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'IV 


MANUAL  OF  CHEMISTRY, 

CONTAINING 

THE  PRINCIPAL  FACTS  OF  THE  SCIENCE, 


THE  ORDER  IN  WHICH  THEY  ARE  DISCUSSED  AND  ILLUSTRATED  IN  THE  LECTURES 


AT 

HARVARD  UNIVERSITY,  N.  E. 

AND 

SEVERAL  OTHER  COLLEGES  AND  MEDICAL  SCHOOLS  IN  THE  UNITED  STATES. 


COMPILED  AND  ARRANGED  AS 

A TEXT  BOOK  FOR  THE  USE  OF  STUDENTS, 

AND  PERSONS  ATTENDING  LECTURES  ON  CHEMISTRY. 


THIRD  EDITION, 

COMPRISING  A SUMMARY  OF  THE  LATEST  DISCOVERIES  AS  CONTAINED  IN  THE  WORKS  OF 
BRANDE,  TURNER,  THOMSON  AND  OTHER  DISTINGUISHED  CHEMISTS,  ILLUSTRATED 
WITH  UPWARDS  OF  TWO  HUNDRED  ENGRAVINGS  ON  WOOD. 


BY  JOHN  W.  WEBSTER,  M.  D. 

ERVING  PROFESSOR  OF  CHEMISTRY  AND  MINERALOGY  IN  HARVARD  UNIVERSITY. 


BOSTON: 

PUBLISHED  BY  MARSH,  CAPEN,  LYON  AND  WEBB. 


Entered  according  to  Act  of  Congress,  in  the  year  1839, 
By  Marsh,  Capen,  Lyon  and  Webb, 

In  the  Clerk’s  Office  of  the  District  Court  of  Massachusetts. 


TUTTLE,  DENNETT  AND  CHISHOLM’S 
POWER  PRESS, 

No.  17  School  Street,  Boston. 


i* 


TO 

JOHN  GORHAM,  M.  D. 

LATE  ERVING  PROFESSOR  OF  CHEMISTRY, 

AND 

JAMES  JACKSON,  M.  D . 

HERSEY  PROFESSOR  OF  THE  THEORY  AND  PRACTICE  OF  PHYSICK,  IN  HARVARD 
UNIVERSITY,  EMERITUS, 

THE 

FOLLOWING  PAGES 

ARE  INSCRIBED. 


Harvard  University,  1823. 


ADVERTISEMENT 


TO  THE  THIRD  EDITION, 


The  two  former  editions  of  this  work  were  based  upon  the  excellent 
Manual  of  Professor  Brande,  but  the  progress  of  chemical  science  has 
rendered  it  necessary  to  deviate  so  much  from  his  arrangement,  that  in  the 
present  edition  it  has  been  entirely  remodelled.  In  several  institutions, 
where  this  work  had  been  in  use  as  a text  book,  it  became  necessary  to 
seek  for  some  other,  in  consequence  of  its  having  become  out  of  print. 

Several  editions  of  Dr  Turner’s  Elements  of  Chemistry  having  ap- 
peared in  this  country,  under  the  able  supervision  of  a gentleman  eminent 
for  his  scientific  attainments,  that  work  was  adopted  in  many  institutions. 
As  Dr  Turner’s  work  was  not  so  practical  and  elementary  as  was 
desirable,  a new  edition  of  it,  calculated  to  meet  the  wants  of  beginners, 
was  commenced  by  the  compiler  of  this,  but  was  subsequently  relinquished 
on  learning  that  Professor  Bache  was  preparing  a new  edition  of  the  former. 

In  August,  1838,  a part  of  this  new  edition  was  published,  since  that 
time  no  more  of  it  has  appeared.  The  delay  was  attributed  to  the 
decease  of  the  author,  but  it  was  soon  aftei;  announced  that  the  publication 
of  the  sixth  edition  of  the  Elements  would  be  continued  by  the  brother  of 
Dr  Turner  and  Professor  Liebig.  A portion  of  their  joint  work  appeared 
in  London,  a part  of  which  was  republished  in  this  country,  and  a few 
pages  followed  in  England  on  organic  chemistry.  More  than  a year  has 
elapsed  and  no  more  has  been  published.  Under  these  circumstances, 
and  at  the  repeated  request  of  gentlemen  connected  with  various  colleges, 
a new  edition  of  this  Manual  was  commenced  and  has  been  completed,  in 
which  is  incorporated  much  of  the  most  important  elementary  part  of 
Turner  and  Liebig’s  work. 

It  was  deemed  advisable  to  reduce  the  size  of  the  work,  and  to  embody 
more  practical  details  and  more  copious  experimental  illustrations,  than 
are  generally  given  in  the  larger  works. 

This  edition  has  therefore  been  compiled  from  the  volumes  of  Turner, 
Brande,  Faraday,  Liebig,  Thomson,  and  others,  and  as  an  introduction 
to  them,  with  no  more  alteration  than  was  required  to  preserve  uniformity 
and  connexion.*  The  frequent  references  and  designation  of  the  writers’ 


* Numerous  errors  (probably  of  the  press)  in  the  English  edition  of  Turner  and  Liebig’s  work 
have  been  corrected. 


VI 


Advertisement. 


names  by  the  initial  letters,  will  enable  those  who  are  desirous  of  studying 
the  subjects  more  in  detail  to  turn  to  the  originals. 

Chemical  formulae  have  been  largely  employed  in  the  present  edition  : 
those  of  Turner  and  Liebig,  so  far  as  they  have  been  used  in  the  three 
parts  of  the  sixth  English  edition  of  Turner’s  Elements  that  have  appeared. 

Dr  Thomson’s  recent  volume,*  the  most  complete  treatise  on  Organic 
Chemistry  which  we  have  in  the  English  language,  has  been  made  the  basis 
of  the  division  to  which  it  relates.  In  that  work  the  author  has,  with  vast 
labour,  collected  and  embodied  the  materials  that  have  been  for  several 
years  accumulating  from  the  labours  of  the  French  and  German  chemists, 
and  which  are  scattered  through  so  many  of  their  works  and  journals. 
Although  in  Organic  Chemistry  the  arrangement  of  Dr  Thomson  has 
been,  for  the  most  part,  followed,  it  has  not  been  rigidly  adhered  to,  as  it 
promised  more  advantage  to  the  beginner  to  connect  the  description  of 
some  substances  more  immediately  with  the  bodies  affording  them. 

As  but  a very  limited  portion  of  time  is  given  to  the  department  of  what 
has  been  usually  called  Animal  Chemistry,  in  most  institutions  and 
courses  of  lectures,  it  was  concluded  that  a very  concise  chapter  would 
answer  the  purpose.  Many  of  the  facts  also  that  have  usually  been 
arranged  in  that  division,  are  previously  alluded  to  in  the  preceding 
chapters.  It  was  therefore  thought  that  the  account  of  animal  substances 
in  the  text  book  of  Dr  Reid,  of  Edinburgh,  with  some  additions,  would 
be  sufficient. 

In  regard  to  chemical  analysis  its  details  have  now  become  so  extended, 
that  they  require  a distinct  work,  and  as  those  who  intend  to  prosecute 
them  must  very  much  rely  upon  their  familiar  acquaintance  with  chemical 
science,  and  refer  to  the  treatises  particularly  devoted  to  this  depart- 
ment, what  related  to  that  subject  in  former  editions  has  been  omitted. 
No  one  who  intends  to  prosecute  chemical  analysis  will  fail  to  consult  the 
ample  details  of  Rose,  Berzelius,  Faraday,  Dumas,  and  the  various 
Journals  and  Transactions  in  which  the  original  analyses  and  papers  have 
appeared. 

Electricity  and  Electro-Magnetism,  are  now  most  usually  discussed 
in  collegiate  courses  of  instruction  in  the  department  of  Mechanical  Phi- 
losophy. 

The  description  of  complicated  apparatus  has  been  avoided,  as  such  is 
seldom  attainable  by  the  pupil  and  not  necessary  for  elementary  study. 
So  also  has  it  been  thought  sufficient  to  refer,  for  abstruse  points  of  theory, 
and  description  of  complicated  processes,  to  original  papers,  to  which 
those  who  zealously  undertake  the  study  of  chemistry  will  necessarily 
have  recourse.  The  full  descriptions  of  processes  in  the  Chemical  Arts , 
given  by  Dr  Ure  in  his  lately  published  Dictionary  of  Arts  and  Manu- 
factures, have  rendered  it  unnecessary  to  retain  many  in  the  present 
edition  of  this  work. 

Copious  tables  of  chemical  formulae  and  of  atomic  weights,  which  had 
been  prepared,  have  been  omitted,  as  it  was  found  that  their  insertion 


Chemistry  of  Organic  Bodies.  London:  1838.  pp.  1076. 


Advertisement . 


Vll 


would  have  materially  increased  the  size  and  expense  of  the  volume,  and 
such  are  at  hand  in  the  larger  works  on  the  science. 

To  the  gentlemen  who  have  aided  the  progress  of  the  work,  by  public 
documents,  valuable  suggestions,  or  written  communications,  the  compiler 
would  express  his  obligations,  especially  to  the  Honorable  John  Quincy 
Adams,  R.  M.  Patterson,  Esq.,  of  the  U.  S.  Mint,  Professor  Silliman, 
A.  A.  Hayes,  Esq.,  Drs  C.  T.  Jackson  and  S.  L.  Dana,  as  also  to 
Francis  Peabody,  Esq.,  of  Salem,  for  his  usual  liberality  in  allowing 
several  new  instruments,  from  his  richly  appointed  laboratory,  to  be  copied 
and  described. 

In  accordance  with  a ,better  taste  which  prevails  among  the  scientific 
men  of  Europe,  all  titles  have  been  omitted,  it  being  deemed  sufficient 
that  the  names  quoted  are  considered  as  authorities . 

Harvard  University,  Cambridge,  1839. 


Note — All  the  articles  of  apparatus  figured  in  this  work  are  now  manufactured  or  fur- 
nished by  N.  13.  Chamberlain,  Philosophical  Instrument  Maker,  School-street,  Boston.  The 
glass  apparatus  is  beautifully  made  by  the  New-England  Glass  Company,  and  Electro-Mag- 
netic Apparatus  by  Daniel  Davis,  Jj  Cornhill,  Boston. 


NOTE. 

The  letter  D.  refers  to  Davy’s  Elements  of  Chemical  Philosophy . 

H.  “ Henry’s  Chemistry. 

U.  “ Ure’s  Dictionary  of  Chemistry. 

M.  “ Murray’s  System  of  do. 

T.  “ Turner’s  1st  and  2d  part. 

Tr5  “ “ Elements , 5th  edition. 

T.  and  L.  refer  to  Turner  and  Liebig’s  continuation. 

T.  in  chap.  ix.  refers  to  Thomson’s  Organic  Chemistry. 

B.  “ Brande’s  Manual. 

F.  “ Faraday’s  Chemical  Manipulation. 


EXPLANATION  OF  PLATES. 


Description  of  Frontispiece. 

Figs.  1 and  2 represent  a modification  of  the  Argand  lamp,  contrived  by  Dr  C.  T.  Jack- 
son,  and  which  he  has  called  oxyalcohol  and  air  blast  lamp. 

Fig.  1.  A,  reservoir  for  alcohol  containing  JO  oz.  measures;  B,  connecting  tube  from 
reserv  oir  to  burner  ; C,  burner  containing  the  elevator  and  blow-pipe;  D,  blast  tube  for  oxy- 
gen or  air  from  the  bellows  or  gasometer ; e e,  inner  cylinder  or  blow-pipe^  expanded  to  a 
trumpet  form  at  top,  where  the  opening  may  be  regulated  by  turning  the  screw  L t,  so  as  to 
bring  it  nearer  or  farther  from  the  interior  lip  of  the  elevator,//,  the  space  ought  to  be  ytW 
inch,  g g.  wick  elevated  by  means  of  a spiral  groove  in  the  elevator,  //,  and  the  outer 
cylinder,  h h,  vylrieti  has  a slit  and  points  to  move  it  by  turning  the  chimney-holder,  i i. 
k k , chimney  made  of  mica  and  supported'  by  two  copper  rings  and  strips,  see  Fig.  3. 

Fig.  2.  The  lamp  ready  for  work.  A,  reservoir;  B,  burner ; C,.  blast  tube  connected 
with  the  gasometer  or  bellows  pipe,  and  controlled  by  a cock  in  order  to  shut  off  or  let  on 
the  blast  at  pleasure;  E,  crucible  of  platina  on  a stand  ring  and  support  fixed  by  the  clamps 
e and/;  g , screw  for  fixing  the  lamp  at  any  required  height  on  the  rod  or  stand ; A,  brass 
retort  ring  for  larger  vessels  used  to  support  a retort,  or  for  evaporations,  digestions,  &c. 

Fig.  3.  Copper  frame  for  a mica  chimney.  The  mica  being  rolled  it  is  inserted  so  that 
the  lapping  edges  come  under  one  of  the  copper  strips,  k k.  When  the  ends  of  the  copper 
strips  are  bent  down  and  pressed  tight  so  as  to  secure  the  mica  in  place  : one  frame  will 
outlast  many  mica  chimneys. 

Fig.  4.  i,  india-rubber  cloth  bag  and  weighty,  for  oxygen  gas,  when  a gasometer  is  not 
at  hand. 

When  the  lamp  is  to  be  used,  the  reservoir  is  charged  with  alcohol  at  90°  strength,  and 
if  oxygen  gas  is  to  be  employed,  a little  “ spirit  gas”  may  be  added,  but  good  alcohol  is 
preferable.  The  cup  is  unscrewed  from  the  bottom  of  the  burner  and  tne  lower  orifice 
closed  by  a good  cork.  The  blast  tube  is  raised  or  depressed  as  required  to  produce  thp 
best  effect  on  the  flame.  The  platinum  crucible  is  heated  to  full  redness  by  the  natural 
current  of  air  ; then^  having  raised  the  wick,  on  urging  a blast  by  means  of  bellows,  a very 
intense  heat  will  be  obtained. 

This  lamp  is  very  powerful  when  used  with’  oil  and  a blast  of  hot  air,  the  air  being 
heated  in  a copper  tube  over  a charcoal  fire  in  a wire  grate  ; ail  the  smoke  is  consumed. 
With  this  lamp  a piece  of  lime  or  magnesia  may  be  as  intensely  ignited  as  in  Drummond's 
apparatus  (251). 

By  throwing  a current  of  oxygen  gas  outside  the  flame,  a more  perfect  combustion  of  oil 
takes  place,  but  the  wick  will  then  require  to  be  elevated  by  means  of  a rack  and  pinion. 
The  outside  current  is,  however,  not  wanted,  a sufficiently  high  temperature  for  most  pur- 
poses being  obtained  without  it. 

These  lamps  are  manufactured  by  Hooper  and  Blake,  Boston. 

Fig.  5,  represents  an  air  pump  constructed  by  Chamberlain,  of  Boston,  for  Harvard  College. 
The  internal  length  of  the  barrel  is  13  inches,  and  the  diameter  4 inches.  The  piston  rod 
passes  through  an  air-tigbtcollar,  the  upper  part  of  which  is  concave,  to  receive  oil,  and  into 
which  the  oil  that  is  thrown  out  when  the  piston  is  elevated,  is  conveyed  by  a small  bent  tube 
passing  out  of  the  upper  flange  over  the  upper  valve.  The  lower  valve  is  formed  by  6 small 
holes  covered  with  leather,  and  there  is  a similar  valve  in  the  upper  flange  opening  upwards. 
By  this  arrangement  the  atmospheric  pressure  is  cut  ofF,  and  after  the  first  stroke  by  which 
the  air  above  the  piston  is  removed,  the  pump  can  be  worked  with  great  ease  and  rapidity. 
Within  the  receiver  on  the  pump-plate,  is  represented  a section  of  an  improved  method  of 
exposing  water  to  sulphuric  acid  (195/  The  glass  dish  has  an  opening  in  its  centre,  on 
the  elevated  edge  of  which  the  small  dish  containing  the  water  is  securely  supported. 
Fig.  6 and  8 represents  the  arrangement  for  covering  the  water  with  a brass  plate,  (see  note 
page  (>0,)  while  the  exhaustion  is  making.  The  plate  is  then  raised  by  means  of  the  rod 
which  passes  through  an  air-tight  cap,  and  the  water  freezes. 


X 


Description  of  Frontispiece. 

The  piston  is  constructed  of  two  plates  of  brass  and  one  piece  of  leather , the  lower 

fdate  being  of  the  same  diameter  as  the  barrel,  the  upper  plate  is  small  enough  to  admit  the 
eather  turning  up  between  it  and  the  barrel ; the  whole  piston  is  only  one  half 
or  five  eighths  of  an  inch  thick.  Fig.  6 is  an  enlarged  section  of  the  barrel  and  piston 
of  the  pump. 

Fig.  7,  represents  De  Luc’s  electrical  columns,  consisting  of  many  hundred  discs  of  sil 
ver-leaf  and  thin  discs  of  zinc,  alternating  with  writing  paper,  or  silvered  paper  and  zinc, 
or  silvered  paper  and  oxide  of  manganese,  so  arranged  within  the  vertical  and  parallel  glass 
tubes,  that  the  dissimilar  metals  are  in  contact,  and  each  pair  thus  formed,  is  separated  by 
the  paper.  The  tubes  are  terminated  by  small  bells  in  metallic  connexion  with  the  upper 
discs.  The  series  commences  with  silver  in  one  tube  and  is  terminated  by  zinc,  or  the 
other  metal  employed,  while,  in  the  other  tube,  the  order  of  the  discs  is  reversed.  A deli- 
cate metallic  clapper  suspended  between  the  columns,  on  a glass  support,  will  be  attracted 
and  repelled.  See  page  92. 

Fig.  9,  is  a representation  of  Clarke’s  electro-magnetic  machine.  A,  horse-shoe  magnets 
confined  to  the  upright  support  by  a clamp  and  screw.  B is  the  armature,  with 
coils  of  silked  copper  wire,  which  revolves  in  front  of  the  poles  of  the  magnets,  mo- 
tion being  communicated  by  the  wheel  C,  which  is  turned  by  the  hand.  D H,  Drake-pie- 
ces. The  terminations  of  the  coils  are  soldered  to  a brass  cylinder,  being  insulated 
by  a piece  of  hard  wood  attached  to  the  brass  stem.  O O,  iron  wire  springs  pressing 
against  the  cylinder  F,  at  one  end  Q,  Q,,  a metal  spring  that  rubs  upon  the  brake-piece 
H.  T,  a bent  copper  wire  connecting  brass  straps,  on  the  block  L Thus  E,  if,  Q,, 
P,  N,  are  in  connexion  with  the  commencements  of  each  coil,  and  F,  O,  M,  with  the  ter- 
minations. 

Fig.  10  shows  the  arrangement  for  decomposing  water  by  means  of  the  above.  Water  is 
placed  in  a glass  tube  B,  in  a glass  vessel  A,  through  the  bottom  of  which  the  platinum 
wires  pass.  To  the  glass  vessel  a brass  cup  is  attached,  from  which  proceed  stout  wires 
passing  into  holes  in  the  brass  straps  on  M and  N.  The  wire  Q,  rubs  on  the  break-piece 
H.  When  the  armature  is  made  to  revolve  the  decomposition  of  the  water  takes  place. 
For  a more  particular  description  see  Clarke’s  account  of  the  instrument,  &c.  in  Amer 
Jour.  vol.  xxx.  100. 

Fig.  11  represents  a new  self-registering  thermometer,  which  was  exhibited  at  the  last 
meeting  of  the  British  Association.  A is  a glass  tube  filled  with  pure  spirit  of  wine.  B is 
a continuation  of  the  same,  but  much  smaller,  which  is  to  be  about  half  full  of  quicksilver 
to  support  the  spirit  in  the  long  tube.  Upon  the  quicksilver  at  G,  i9  a float  supporting 
the  wire  C,  which  wire  has  a knee  or  bend  in  it,  with  a small  eye,  which  runs  upon  the 
fixed  wire  D,  carrying  an  index  or  pointer ; E is  the  scale  whicn  must  be  made  experi- 
mentally. If  any  change  takes  place  in  the  bulk  of  the  spirit,  the  quicksilver  is  also  af- 
fected, and  with  the  silver  the  ivory  float  G,  carrying  the  index  or  pointer,  which  shows  at 
once  the  degree  of  temperature  upon  the  scale  ; this  is  the  simple  action  of  the  thermome- 
ter- To  make  it  register,  the  two  light  indexes  or  pointers  F,  move  upon  the  wire  D,  their 
own  friction  keeping  them  wherever  they  are  placed.  To  set  it,  the  pointer  F,  below  the 
thermometer’s  index,  must  be  pushed  close  up  to  it,  and  the  pointer  F,  above,  pushed  down 
it ; and  it  is  evident  that  if  any  change  of  temperature  takes  place,  the  thermometer’s  in- 
dex will  move  the  registering  index  eithei  above  or  below,  and  leave  it  there,  thereby 
showing  the  extreme  rise  and  fall  of  the  thermometer  in  any  given  time  The  action 
of  the  air  upon  the  quicksilver  is  also  provided  against  EigJuk  Rep.  Brit.  Assoc.  1839 


I 


PLATE  1 


PLATE 


II. 


Plate  I.  Apparatus  for  the  Solidification  of  Carbonic  Acid , 

Fig.  1.  A.  A cylinder  of  wrought  iron,  23  inches  in  length,  4 in  diameter,  terminated  by 
cast  iron  hemispheres;  supported  by  two  gudgeons  on  an  iron  frame,  upon  which  it  revolves. 

d.  A copper  tube  closed  at  bottom,  for  holding  acid. 

D.  The  same  j.  brass  hook  for  removing  the  acid  holder. 

Fig.  2.  B.  Cylinder  of  wrought  iron  to  receive  the  gas.  Of  the  same  size  as  A. 

h.  A small  tube  passing  down  to  within  a short  distance  from  the  bottom,  up  which  the  lique- 
fied gas  is  forced  by  the  pressure  of  the  gas  above. 

E.  A brass  box,  4 inches  in  diameter  4 in  depth,  to  receive  the  solidified  gas. 

o.  The  same  without  the  cover,  shewing  the  interior  ; the  horizontal  pipe,  (the  mouth  of  which 
is  also  seen  in  E,  under  the  upper  clamp  by  which  and  the  one  below,  the  cover  is  confined  when 
the  box  is  used,)  fits  upon  a short  jet  3.  The  centre  of  each  part  of  the  box  is  pierced  with  several 
small  holes  communicating  with  the  wooden  handles,  which  are  hollow  and  open  to  allow  of  the 
escaj  e of  the  expanding  gas-  In  front  of  the  inner  mouth  of  the  horizontal  pipe  is  a short  curved 
slip  oi  sheet  brass  for  tne  purpose  of  preventing  the  solidified  gas  being  too  rapidly  driven  out 
of  the  handles. 

f.  A copper  pipe  16  inches  in  length  and  | inch  in  diameter,  terminated  by  connecting  pieces, 
by  meansot  which  the  two  iron  cylinders  can  be  connected,  for  the  transfer  of  the  gas. 

g.  A hold-fast  of  iron  with  a small  projection  that  fits  into  the  hole  W in  fig.  1.  By  this  the 
cylinder  can  be  secured  from  turning  when  the  plug  or  valve  is  opened. 

li . A wrench  for  turning  the  plug 

i.  Small  brass  wrench  for  turning  the  steel  screw  of  the  valve-plugs  in  the  upper  parts  of  the 
cylinders  A.  B. 

m.  A vessel  of  zinc,  holding  the  quantity  of  water  required  for  each  charge. 

n.  A funnel  of  zinc  for  introducing  the  carbonate  of  soda  into  the  cylinder  A. 

Fig.  3-  Section  of  one  of  the  connecting  screws  and  pipe ; the  small  projecting  part  on  the 
flange  of  the  pipe  fits  into  the  outlet  of  the  screws  of  the  valve  plugs  l and  2. 

The  cylinder  A may  be  called  the  Generator,  B the  Receiver.  The  materials  employed  for 
each  charge  of  the  Generator,  are,  Bicarbonate  of  Soda  in  powder  2|  lbs.  ; Water  at  100°  6£ 
lbs.;  Sulphuric  acid  1 lb.  7^  oz.  . „ 

The  valve  plugs  are  of  brass  and  alike,  but  a section  of  one  only  is  represented  (in  Fig.  1.  A.) 
with  a double  cone  of  steel,  which  is  accurately  ground  to  its  seat ; the  stem  is  cut  into  a fine 
screw  and  passes  through  the  upper  part  of  the  valve-plug,  it  is  screwed  up  or  down  by  means 
of  the  wrench  i having  a square  hole  into  which  the  square  end  of  the  stem  fits.  It  will  be 
seen  that  when  the  cone  is  screwed  up  there  is  an  outlet  for  any  gas  from  the  cylinder  through 
the  horizontal  branch  of  the  valve-plug,  and  when  it  is  screwed  down  the  passage  is  closed. 
The  opening  under  the  cone,  through  the  lower  part  of  the  valve-plug,  is  one  tenth  of  an  inch 
diameter.  When  the  cone  is  screwed  up  no  gas  can  escape  above  it,  as  the  upper  part  is  also  well 
ground  to  a conical  cavity. 

To  charo-e  the  generator.  Unscrew  the  valve  plug  and  remove  it  from  the  end  ot  the  cylinder  ; 
through  the  funnel  n pour  in  the  soda  salt;  add  the  warm  water,  remove  the  funnel,  and  with  a 
stick  stir  the  salt  and  water,  breaking  down  any  lumps.  Pour  the  sulphuric  acid  into  the  copper 
acid  holder  D,  and  with  the  hooky  introduce  it  into  the  generator.  Remove  the  hook  and  having 
carefully  cleaned  all  the  screws  with  a tooth  brush  (not  with  a cloth)  and  oiled  them,  screw  in 
the  valve  plu^  making  it  secure  by  the  aid  of  ihe  wrench  and  holdfast.  Screw  down  the  steel 
valve  firmly.°  Turn  the  generator  and  cause  it  to  revolve  several  times,  that  the  acid  may  be 
thrown  upon  the  soda  ; repeat  this  and  occasionally  allow  the  cylinder  to  remain  with  the  valve 
downward.  Let  the  generator  remain  5 or  10  minutes  in  the  position  represented  in  the  plate, 
until  the  gas  has  disengaged  itself  and  collected  in  the  upper  part  of  the  cylinder  Haying  pre- 
viously cooled  the  receiver  in  iced  water  (in  which  it  should  be  immersed  up  to  the  valve)  con- 
nect it  with  one  end  of  the  pipe/  securing  the  screw  with  a wrench.  Connect  the  other  end  ol 
the  pipe  with  the  valve  plug  of  Fig.  2.  B also  very  firmly.  Open  the  steel  valve  of  the  receiver 
by  screwing  it  up  entirely — then,  slowly,  and  partially,  open  that  of  the  generator.  the  Sas 
will  pass  over  and  in  about  two  minutes  the  pressure  will  be  equalized,  no  more  gas  then  pass- 
ing • close  the  steel  valve  of  the  receiver  and  then  that  of  the  generator.  Disconnect  the  gen- 
erator, open  the  valve  to  allow  the  remaining  gas  to  escape,  having  a vessel  ready  to  receive  the 
liquid  which  soon  follows.  When  no  more  liquid  passes  out,  remove  the  valve-plug,  place  it  m 
a basin  of  clear  water ; and  having  lifted  out  the  acid  holder,  pour  out  the  sulphate  ot  soda 
and  wash  out  the  inside  of  the  generator  with  water.  Repeat  the  charges  in  the  same  manner 


XIV 


Explanation  of  Plates. 


as  long  as  any  gas  is  heard  to  pass  from  the  generator  to  the  receiver.  Nine  charges  I have 
^usually  found  sufficient,  which,  if  well  managed,  will  completely  till  the  box  E with  solid  gas 
‘several  times. 

To  obtain  the  solid.  Having  previously  cooled  the  box  in  ice,  wipe  it  dry  and  secure  the  top 
on  with  the  clamps.  Screw  the  coupling  and  short  jet  (3)  upon  the  valve  plug  (as  represented  I) 
of  the  Receiver.  Place  the  receiver  between  the  knees,  and  the  box  upon  the  jet.  Open  the 
steel  valve,  slowly,  until  a white  vapour  issues  from  the  handle^  of  the  box;  gradually  enlarge 
the  opening,  and  when  the  brass  box  has  become  thickly  covered  with  the  condensed  and  frozen 
vapour  of  the  apartment,  the  farther  escape  of  the  gas  may  be  stopped  by  closing  the  valve.  On 
removing  the  box  and  opening  it,  the  while  solid  acid  will  be  found  within. 

The  greatest  care  is  necessary  to  avoid  introducing  any  dirt,  fibres  of  wood,  cloth,  &c.  into 
the  vessels,  as  they  are  liable  to  be  forced  under  the  valves  and  into  the  small  tubes  oud  thus 
defeat  the  process. 


Plate  II. 


Figs.  I and  2 represent  a method  of  washing  precipitates  : which  will  bo  often  found  use 
ful.  By  this  arrangement  a column  of  pure  water  can  be  made  continually  to  pass  through  a 
powder  or  precipitate.  A flask,  or  bottle  a,  fig.  2,  is  filled  with  water  and  is  closed  by  a cork, 
having  a glass  tube  of  the  shape,  fig.  1,  passed  through  it.  This  tube  may  be  about  four  inches 
in  length  and  half  an  inch  iu  diameter.  When  the  flask  or  bottle  is  inverted  as  in  fig.  2 u,  the 
water  will  run  out  only  till  the  air  within  it  is  expanded  to  a certain  degree,  the  capillarity 
of  the  tube  a fig.  I,  not  allowing  the  escape  of  any  water  into  the  air.  But  if  the  tube  <i  is 
plunged  into  a liquid,  the  water  from  the  flask  or  bottle  will  flow  into  the  liquid.  As  the  air  ex- 
pands the  water  is  forced  down  the  tube  d and  a bubble  of  air  passes  from  d through  b and  as- 
cends into  the  bottle.  A correponding  quantity  of  water  is  forced  down,  and  every  successive 
bubble  of  air  has  the  same  effect.  This  water  flows  out  at  the  point  a.  and  if  that  point  is  dip- 
ped into  a liquid  contained  in  a funnel,  the  level  of  the  water  in  the  latter  is  kept  at  the  same 
point,  as  for  example  at  the  linec,  fig.  1.  Fig.  2 exhibits  the  arrangement,  with  a vessel  below  to 
receive  the  filtered  liquid. 

Fig.  3,  4,  5.  Gahn’s  cylinder  holder  for  flasks,  cylinders,  jars,  6ic.  5 represents  the  principal 
portion  of  this  apparatus  (seen  from  above).  Fig.  4,  exhibits  the  same  in  profile.  The  instru- 
ment is  made  of  wood.  A slit  Jtb  of  an  inch  deep  is  made  in  the  block  at  u b , and  in  this  slit  a 
strong  baud  or  ribbon  of  the  same  width,  is  placed,  the  end  of  it  being  secured  bv  a thick  edge 
or  seam  down  the  side  b.  The  end  of  this  hand  is  then  carried  round  from  a,  in  the  direction 
A h G t E and  through  the  slit  fgt  (fig.  4.)  into  the  conical  hole  C,  where  it  is  fastened  in 
another  slit  k t,  cut  in  the  conical  peg  D.  The  band  is  wound  up  round  the  conical  peg  and  fixed, 
when  necessary,  by  pressing  the  peg  into  the  conical  hole.  The  band  can  be  loosened  by  slack- 
ening the  conical  peg.  If  a glass  cylinder  as  G (tig.  o)  is  placed  in  the  triangular  opening  h i it 
can  be  held  fast  or  let  loose  at  pleasure.  The  other  part  of  this  apparatus  consists  of  a frame 
(fig.  3)  I H M,  which  can  be  screwed  to  the  side  of  a pneumatic  trough  by  the  screw  at  M.  The 
upright  rod  D is  cylindrical,  the  arm  I square  and  adapted  to  the  square  hole  F in  fig.  4.  The 
screws  N and  K permit  any  required  adjustment. 

Fig.  6 represents  a convenient  apparatus  for  coudensing  vapours,  o b,  A tube  of  tin  2 inches 
wide  17  inches  long,  c,  A leaden  pipe  passing  along  inside  to  within  an  inch  of  each  extremity  of 
the  tin  tube,  it  is  open  at  the  lower  end,  but  passes  through  the  wide  tube  near  the  top  termi- 
nating in  a funnel,  e,  A pipe  entering  the  upper  side  of  the  larger  tube,  close  to  where  tne  other 
pipe  passes  out,  and  hanging  down  an  inch  or  two  below  the  wide  tube.  This  short  tube  is  open 
at  both  ends.  A glnss  tube,  23  inches  in  length,  is  placed  into  the  tin  tube  through  corks  at  a 
and  b which  fit  the  latter  and  prevent  the  passage  of  water.  The  glass  tube  should  he  somewhat 
tapering,  about  an  inch  wide  at  the  upper  end  and  rather  less  than  half  an  inch  at  the  lower  end. 
The  upper  end  should  be  bordered  or  have  a rim,  so  as  to  permit  the  insertion  of  a cork.  Water 
poured  into  the  funnel  d can  only  escape  after  traversing  the  tube  at  e and  thus  the  glass  tube  can 
be  kept  surrounded  by  cold  water. 

Fig.  7.  Cooper’s  mercurial  receiver,  d d,  The  receiver  to  be  filled  with  mercury;  a basin  is 
placed  below  the  mouth  to  receive  what  may  be  displaced  by  the  gas  as  it  passes  in  from  the 
flask  a. 

Fig.  8 represents  Seffstroem’s  support,  made  entirely  of  wood.  The  pieces  can  be  adjusted  by 
means  of  the  screws,  to  grasp  a vessel  or  tube  and  support  it  at  any  desired  height  or  angle. 

Fig.  9.  Hare's  apparatus  for  exploding  hydrogen  and  chlorine.  A flask  is  half  filled  with 
chlorine  and  transferred  to  the  pan  P with  its  orifice  over  that  of  'a  pipe  communicating  with  the 
cock  C and  flexible  pipe  extending  to  a self- regulating  reservoir . (Fig.  120,  page  123)  of  hydro- 
gen. The  flask  is  surrounded  with  a cylinder  of  wire  gauze.  Just  before  the  explosion  is  de- 
sired hydrogen  is  admitted  to  displace  the  water  left  in  the  flask.  The  pan  should  contain  water 
sufficient  to  cover  the  mouth  of  the  flask.  A mirror  is  used  to  reflect  the  solar  rays  upon  the 
flask.  See  Amer.  Jour.  xxix.  243. 


CONTENTS 


CHAPTER  I. 

Of  the  Powers  and  Properties  of  Matter , and  of  the  General  Laws  of 

Chemical  Changes. 


Section  I. 

II. 

III. 

IV. 

V. 


ATTRACTION, 

AFFINITY, 

HEAT  OR  CALORIC, 
LIGHT, 

ELECTRICITY, 


CHAPTER  II. 


Section  I. 

II. 


NOMENCLATURE, 

APPARATUS  AND  MANIPULATION, 


i02 

106 


CHAPTER  III. 


Inorganic  Chemistry. 


I. 

OXYGEN, 

• 

• 

IL 

HYDROGEN,  . 

• 

• 

III. 

NITROGEN, 

. 

IV. 

CARBON, 

. 

V. 

SULPHUR, 

VI. 

PHOSPHORUS, 

• 

• 

VII. 

BORON,  . 

• 

VIII. 

SILICON, 

• 

IX. 

SELENIUM, 

X. 

CHLORINE,  . 

. 

XI. 

IODINE, 

XII. 

BROMINE, 

• 

. 

XIIL 

FLUORINE, 

118 

122 

134 

151 

161 

169 

175 

176 
178 
180 
196 
202 
205 


Compounds  of  Simple  Non-Metallic  Acidifable 

other. 


Combustibles  with  each 


7 


XIV. 

HYDROGEN  AND  NITROGEN— AMMONIA, 

208 

XV. 

HYDROGEN  AND  CARBON, 

. . 211 

XVI. 

HYDROGEN  AND  SULPHUR, 

214 

XVI 


Contents. 


Section  XVII.  HYDROGEN  AND  SELENIUM, 

XVIII.  HYDROGEN  AND  PHOSPHORUS, 

XIX.  NITROGEN  AND  CARBON, 

XX.  SULPHUR  AND  CARBON, 


217 

217 

219 

220 


CHAPTER  IV. 


Metals. 


Section  I.  GENERAL  PROPERTIES,  ... 

II.  METALLIC  BASES  OF  THE  ALKALIES. 

Potassium,  ...... 

Sodium,  ...... 

Lithium,  ...... 

III.  METALLIC  BASES  OF  THE  ALKALINE  EARTHS. 

Barium,  . ...... 

Strontium,  ...*.. 

Calcium,  ....... 

Magnesium,  ...... 

IV.  METALLIC  BASES  OF  THE  EARTHS. 

Aluminium,  ...... 

Glucinium,  ...... 

Yttrium,  ...... 

Thorium,  . . . . . . 

Zirconium,  ...... 

V.  METALS,  THE  OXIDES  OF  WHICH  ARE  NEITHER  ALKALIES 

NOR  EARTHS. 

METALS  WHICH  DECOMPOSE  AT  A RED  HEAT. 

Manganpse, 

Iron, 

Zinc, 

Cadmium, 

Tin,  . 

Cobalt, 

Nickel, 

VI.  METALS;  WHICH  DO  NOT  DECOMPOSE  WATER,  &c. 

Arsenic,  ..... 

Chromium, 

Vanadium, 

Molybdenum, 

Tungsten, 

Columbium, 

Antimony, 

Uranium, 

Cerium, 

Bismuth, 

Titanium, 

Tellurium, 

Copper, 

Lead, 

VII.  METALS,  THE 
RED  HEAT. 

Mercury,  . 

Silver, 

Gold, 


OXIDES  OF  WHICH  ARE  REDUCED  AT  A 


222 

229 

234 

237 

237 

239 

240 
245 

247 

248 

249 

250 
250 


251 

256 

263 

264 

265 
268 

270 

271 
277 
280 
282 

283 

284 

285 
2S9 

289 

290 

291 

293 

294 
298 


301 

307 

312 


Contents. 

Platinum, 

Palladium, 

Rhodium, 

Osmium  and 
Iridium, 

Latanium, 


CHAPTER  V. 


Section  I.  SALTS. 

Order  1.  Oxysalts,  * 
Sulphates, 

Double  Sulphates,  . 
Sulphites, 

Nitrates,  . 

Chlorates, 

lodates, 

Phosphates, 

Arseniates, 

Chromates, 

Borates, 

Carbonates, 

II.  Order  2.  Hydro-salts,  . 

III.  Order  3.  Sulphur-salts, 

IV.  Order  4.  Haloid-salts,  . 


CHAPTER  VI. 

Organic  Chemistry. 


Section  I. 


II. 


VEGETABLE  PRINCIPLES, 
Theory  of  Amides, 

“ of  Benzoyl, 

“ of  Ethers,  . 

“ of  Pyracids, 

“ of  Substitutions, 

VEGETABLE  ACIDS. 

Oxalic  acid, 

Rhodizonie  acid, 

Croconic  acid, 

Formic  acid, 

Mellitic, 

Succinic  acid, 

Acetic  acid, 

Lactic  acid, 

Benzoic  acid,  . 

Malic  acid, 

Citric  acid, 

Tartaric  acid, 

Meconic  acid,  . 

Gallic  acid, 

Kinic  acid, 

Tannic  acid, 

Stearic  acid, 

Margaric  acid, 

Oleic  acid, 

Azulmic  acid, 


XV 11 
316 


31® 


320 


* 

320 

321 
330 
332 
332 
339 

341 

342 

345 
344 

346 

347 
353 
355 
558 


362 

364 
365, 

365 

366 
366 

369 

373 

373 

373 

375 

375 

376 

380 

381 

382 

383 
383 

386 

387 

388 
388 
390 

390 

391 
391 


xviii  Contents. 

Indigotic  acid, 

392 

Carbazotic  acid, 

392 

Pectic  acid,  , . . 

# 

393 

Crenic  acid, 

394 

Apocrenic  acid, 

394 

Althioaic  acid,  . i 

394 

Eth ionic  acid,  . . 

395 

0 Sulphonaphthalic  acid,  . . 

395 

Su'pho-indigotic  acid, 

395 

Formo-benzoilic  acid, 

395 

III.  CYANOGEN  AND  ITS  COMPOUNDS, 

396 

Mellon,  .... 

396 

Melamiu,  . . , 

396 

Melain,  .... 

397 

Ammclin, 

397 

Ammelid, 

398 

Cyanic  acid, 

398 

Fulminic  acid, 

401 

Cyanuric  acid, 

403 

Cyamelid,  . . 

405 

Hydrocyanic  acid,  . . 

405 

Cyanurets,  • . 

409 

Hydroferrocyanic  acid,  . . 

412 

Ferrocyanurcts, 

413 

Ferrid -cyanogen,  • . 

417 

. Hydro  ferridcyanic  acid, 

417 

Chlorides  of  Cyanogen, 

419 

Iodides  of  “ 

419 

Cyanogen  and  Sulphur, 

420 

and  Water, 

421 

and  Ammonia,  . 

422 

Cyanilic  acid, 

422 

IV.  HYPOTHETICAL  COMPOUNDS  OF  CYANOGEN 

AND 

CAR- 

BONIC  OXIDE, 

423 

Uric  acid, 

423 

Allantoin, 

425 

Alloxan,  v 

425 

Alloxanic  acid, 

426 

Mesoxalic  acid, 

427 

Mykomelinic  acid,  . « 

427 

Parabanic  acid,  . . . 

423 

Oxaluric  acid,  . . . 

428 

Thionuric  acid,  . 

429 

Uramil, 

429 

Uramilic  acid.  . . • 

430 

Alloxantin, 

430 

Murexid,  . 

431 

Murexan, 

433 

Uric  oxide,  . 

• 

433 

Cystic  oxide, 

• 

433 

CHAPTER  VII. 

I 

Section  l.  VEGETABLE  ALKALIES,  . 

. 

434 

Cinchonia,  . 

. 

. 

, 

435 

Contents 


xix 


Quinia,  .......  435 

Salicin,  ....*•  436 

Veratria,  ......  437 

Strychnia,  .....  . 437 

Narcotina,  ......  437 

Morphia,  ......  438 

Codeia,  .......  440 

Narceia,  • . . : 440 

Thebaia,  ......  . 440 

Meconia,  ......  440 

Brucia,  ....*..  440 

Conia,  ......  440 

Parillia,  .......  440 

Nicotina,  ......  441 

II.  INTERMEDIATE  BODIES,  . . . .441 

Alcohol,  . . . . . . 441 

Aldehyde,  ......  446 

Acetal,  ....*.  447 

Chloral,  . . . . . . .443 

Ethal,  ......  448 

Sulphuric  ether,  ......  448 

Hydrochloric  ether,  . . . . . 451 

Mercaptan,  ......  452 

Nitric  ether,  ......  453 

Oxalic  ether,  , . • . • • 453 

CEnauthic  ether,  .....  454 

Pyroxylic  spirit,  . .....  454 


CHAPTER  VIII. 


Section  I. 

COLOURING  MATTERS,  . 

455 

CHAPTER  IX. 

Section  I. 

OLEAGINOUS  SUBSTANCES, 

. . 458 

II. 

VOLATILE  OILS, 

461 

Resins,  ..... 

463 

Balsams,  .... 

464 

III. 

GUM  RESINS,  .... 

466 

IV. 

NEUTRAL  VEGETABLE  PRINCIPLES,  . 

467 

Oxamide,  .... 

467 

Benzoyl,  .... 

468 

Spiroil,  . 

469 

Sugar,  .... 

469 

Amylaceous  substances, 

471 

Starch,  . 

471 

Amidin,  ..... 

472 

Hordein,  •'  - 

473 

Lignin,  . 

473 

Xyloidine,  . 

473 

Gums,  ..... 

473 

Glutinous  substances, 

474 

Albumen,  .... 

474 

Emulsin,  .... 

475 

XX 


Caoutchouc, 

Extractive, 


Contents. 


476 

477 


Products  of  the  Destructive  Distillation  of  Vegetable  Substances. 


Naphtha,  477 

Paraffin,  ......  477 

Eupion,  .......  477 

Creosote,  * . . . . . 478 

Picamar,  ......  479 

Pittacal,  ......  479 

Capnomor,  ......  479 

Naphthalin,  ......  479 

Coal  gas,  . . „ , . .480 

Oil  gas,  . . . . .481 

Animal  charcoal,  .....  481 

V.  OF  THE  PARTS  OF  PLANTS,  . .482 

Woods,  ......  483 

Leaves,  .......  484 

Flowers,  ......  484 

Seeds,  ......  485 

Fruits,  ......  486 

Colouring  matter,  ......  486 

VI.  PHENOMENA  AND  PRODUCTS  OF  FERMENTATION.  . 4S7 

Beer,  . . . . . .487 

Wine,  ......  488 

Acetous  fermentation,  .....  489 

Panary  fermentation,  .....  490 

Putrefaction,  ......  490 


CHAPTER  X. 

Animal  Substances. 

Sectioh  I.  ULTIMATE  PRINCIPLES  OF  ANIMAL  MATTER,  AND  PRO- 


DUCTS OF  ITS  DESTRUCTIVE  DISTILLATION,  490 

II.  FIBRIN,  .......  492 

Albumen,  ......  492 

Gelatine,  ......  493 

Osmazome,  ......  493 

III.  BONE,  MUSCLE,  &c.  . . . . .493 

IV.  BLOOD,  RESPIRATION,  ANIMAL  HEAT,  . 494 

V.  SALIVARY  AND  GASTRIC  JUICES,  BILE,  &c.  . 600 

VI.  MILK  AND  CHYLE,  . . . . .601 

VII.  OLEAGINOUS  AND  FATTY  SUBSTANCES,  . 602 

VIII.  MUCUS,  PUS,  &c.  . . . . .603 

IX.  UREA-URINE,  .....  504 

Urinary  calculi,  ......  505 


ADDENDA. 

I 

Radiation  of  Caloric,  .......  506 

Influence  of  Colour  on  Absorption  of  Odours,  .....  506 

Compound  blow-pipe,  .......  507 


Contents. 


xxi 

Photographic  Drawing,  .......  507 

Detection  of  Iodine  and  Bromine,  .....  503 

Oxide  of  Phosphorus,  .......  503 

Detection  of  Nitric  Acid,  ......  509 

Detection  of  Nitrogen,  ........  509 

Indelible  Ink,  ........  509 

Salts  of  Baryta  and  Strontia,  ......  609 

Ethyle,  . . . . . . . . 509 

Diastase,  ........  510 

Dextrine,  ........  510 

Nature  of  Ferment,  . . . . . . .511 

Respiration  of  Plants,  . . . . . . . 5 1 1 

New  Compound  of  Mercury,  .......  512 


APPENDIX. 


Chemical  Formulae,  ....... 

Wollaston’s  Scale,  ....... 

Table  of  Elastic  Force  of  Vapour,  ..... 

“ “ « of  « 

“ “ u of  Vapours  of  Alcohol  and  Ether,  . . . 

“ of  the  Quantity  of  Oil  of  Vitriol  and  Anhydrous  Acid, 
u of  Muriatic  (Hydrochloric)  Acid,  ..... 
u of  the  Quantity  of  Real  or  Anhydrous  Nitric  Acid,  . 

“ of  Lowitz,  showing  the  Quantity  of  Absolute  Alcohol  in  spirits  of  different 
gravity,  ........ 

Specific  Gravity  of  Essential  Oils,  ..... 

“ “ of  Oils  of  Fermented  Liquors,  .... 

Table  of  Weights  and  Measures,  ..... 

Description  of  Apparatus  for  Obtaining  Potassium,  &c. 

Barium,  Strontium  and  Calcium,  ..... 

Absorption  of  Gases  by  Charcoal,  ..... 

General  Index,  ...... 

Index  to  Plates. 


specific 


513 

513 

517 

618 

520 

521 

522 
623 

524 

525 
525 
625 
628 
529 
630 
531 


I 


ERRATA. 


Pago  10. 
“ 10. 
44  50. 

44  50. 

44  C4. 

44  65. 

“ 79. 

44  95. 

“ 107. 
“ 115. 
44  115. 
« 120. 
“ 125. 
44  161. 
44  166. 
“ 184. 
“ 209. 
“ 213. 
“ 219. 
“ 257. 
44  272. 

388. 
44  468. 


Line  17,  for  “system  ” read  systems. 

Line  20,  for  “ square  prismatic  " read  double  oblique  prismatic. 
After  “ 176,”  insert  7. 

Before  “A  curious  ” insert  8. 

Foot  note,  for  “ Hares’s  ” read  Hare’s. 

Third  line  for  “ 11°  ” read  41°. 

5th  line,  for  sjUxt^ov  read  tjJLsxtsov. 

4th  line,  for“  smaller  ” similar. 

Top  of  page  for  “ Gasometers  ” read  Graduated,  vessels. 

Lino  28,  lor  “ substract  ” read  subtract. 

Line  29,  ditto. 

Foot  note,  the  reference  should  be  to  Frontispiece. 

For  “ Doebereiner  ” read  Dobereiner. 

In  margin,  for  “ sodidum  ” read  sodium. 

6th  line,  for  “ sulphurious  ” read  sulphurous. 

12th  line,  for  “sodium  ” read  salts. 

Paragraph  732  for  “ ammonical  ” read  ammoniacal. 

In  the  Formula  for  Olefiant  gas,  add  2 after  the  second  H 
Last  line,  for  “ mercury  ” read  Hydrocyanic  acid. 


5th  line  for  Fe  read  Fe. 

In  margin,  dele  “ Poisonous  effects.” 

Line  29,  for  “ whortleberry  ” read  bear-berry. 
Line  29,  for  44  benzoly”  read  benzoyl. 


MANUAL  OF  CHEMISTRY. 


CHAPTER  I. 

• ' . • ' •_  • V . 

OF  THE  POWERS  AND  PROPERTIES  OF  MATTER  AND  OF  THE 
GENERAL  LAWS  OF  CHEMICAL  CHANGES. 

1.  It  is  the  object  of  Chemistry  to  investigate  all  changes  in  the  object  of 
constitution  of  matter,  whether  effected  by  heat,  mixture  or  other  chemistry;, 
means.* 

Most  of  the  substances  belonging  to  our  globe  are  constantly  un- 
dergoing alterations  in  sensible  qualities,  and  one  variety  of  matter 
becomes  as  it  were  transmuted  into  another.  Such  changes, 
whether  natural  or  artificial,  whether  slowly  or  rapidly  performed, 
are  called  chemical. t The  ends  of  this  branch  of  knowledge  are  the 
application  of  natural  substances  to  new  uses,  for  increasing  the 
comforts  and  enjoyments  of  man,  and  the  demonstration  of  the  order, 
harmony,  and  intelligent  design  of  the  system  of  the  earth. 

2.  The  foundations  of  chemical  philosophy  are  observation,  expe-  pounja., 
riment,  and  analogy.  By  observation,  facts  are  distinctly  andtions. 
minutely  impressed  on  the  mind.  By  analogy,  similar  facts  are 
connected.  By  experiment,  new  facts  are  discovered;  and  in  the 
progression  of  knowledge,  observation,  guided  by  analogy,  leads  to 
experiment,  and  analogy,  confirmed  by  experiment,  becomes  scientific 
truth.  D.1,2. 


* The  word  Chemistry  seems  to  be  of  Egyptian  origin,  and  to  have  been  originally  0ri„in  nf  lhe 
equivalent  to  our  phrase  natural  philosophy  in  its  most  extensive  sense.  In  process  of  term, 
time  it  seems  to  have  acquired  a move  limited  signification,  and  to  have  been  confined 
to  the  art  of  working  metals.  In  the  third  century,  we  find  it  used  in  a much  more 
limited  sense,  signifying  the  ar£  of  making:  gold  and  silver.  Those  who  professed 
this  art  gradually  assumed  the  form  of  a sect,  under  the  name  of  Alchemists  ; a term 
which  is  supposed  to  be  merely  the  word  chemist,  with  the  Arabian  article  al  prefixed. 

The  great  object  of  the  alchemists  was  to  find  out  the  means  of  converting  the  baser 
metals  to  gold,  and  the  grand  instrument  by  which  this  was  to  be  effected  was  the 
philosopher’s  stone.  T.  i.  19. 

t Chemistry  is  the  science  which  treats  of  those  events  and  changes  in  natural  bo-  Definitions, 
dies,  which  are  not  accompanied  by  sensible  motions.  T-  i.  18. 

It  is  the  object  of  Chemistry  to  discover  and  explain  the  changes  of  composition  that 
occur  among  the  integrant  and  constituent  parts  of  different  bodies.  H.  i.  12. 

1 


2 


Chap.  I. 

Arrange- 

ment. 


Attraction 
at  sensible 
distances. 


Weight. 

Particles 

bodies. 


Atoms. 


Contiguous 

attraction. 


Cohesion. 


Effects  of 
attraction 
at  insensi* 
ble  distan- 
ces. 


Attraction — Particles  of  bodies. 

3.  In  the  present  state  of  our  knowledge,  it  will  be  most  conve- 
nient to  begin  the  study  of  chemistry  with  the  discussions  relating  to 
the  general  powers  or  properties  of  matter,  and  afterwards  to  proceed 
to  the  examination  of  individual  substances,  and  to  the  phenomena 
which  they  offer  when  presented  to  each  other  under  circumstances 
favorable  to  the  exertion  of  their  mutual  chemical  agencies. 

The  powers  and  properties  of  matter,  connected  with  chemical 
changes,  maybe  considered  under  the  heads  of  1,  Attraction ; 2, 
Heat;  3,  Electricity;  4,  Light. 


Section  I.  Attraction. 

4.  All  bodies  composing  the  material  system  of  the  universe  have 
a mutual  tendency  to  approach  each  other.  The  operation  of  this 
force  extends  to  the  remotest  parts  of  the  planetary  system.  The 
smaller  bodies,  that  are  under  our  more  immediate  observation,  are 
influenced  by  the  same  power,  and  fall  to  the  earth’s  surface,  when 
not  prevented  by  the  interference  of  other  forces.  From  these  facts 
the  existence  of  a property  has  been  inferred,  which  has  been  called 
attraction , or  more  specifically,  the  attraction  of  gravitation.  Its 
nature  is  entirely  unknown  to  us.  The  attraction  between  these 
bodies  takes  place  at  sensible  distances  : it  exists  in  all  known  form6 
of  matter  ; and  it  acts  upon  them  directly  as  the  mass,  and  inversely 
as  the  square  of  the  distance. 

5.  The  force  required  to  separate,  a body  from  the  surface  of  the 
earth,  or  prevent  it  from  descending  towards  it,  is  called  its  weight. 

G.  Of  the  nature  of  the  particles  of  which  bodies  are  composed, 
we  have  no  satisfactory  evidence.  In  simple  bodies  they  must  be  all 
of  the  same  nature,  or  homogeneoics.  In  compound  bodies,  we  un- 
derstand by  the  term  particles , the  smallest  parts  into  which  bodies 
can  be  resolved  without  decomposition.  The  word  atom * denotes 
both  these  kinds  of  particles.  When  two  atoms  of  different  kinds 
unite  to  form  a third  or  compound  atom,  we  may  term  the  two  first 
component  atoms;  and  if  these  have  not  been  decomposed,  they  may 
be  called  elementary  or  primary  atoms.  H.  i,  29. 

7.  The  attraction  exerted  between  these  minute  particles,  or  atoms, 
when  they  are  placed  in  apparent  contact,  and  which  is  effective  only 
at  insensible  distances,  has  been  called  contiguous  attraction , and  has 
been  distinguished  as  it  is  exerted  between  particles  of  matter  of  the 
same  kind,  or  between  particles  of  a different  kind.  When  the  par- 
ticles of  the  same  kind  are  united  to  form  an  aggregate  or  mass,  they 
are  sometimes  said  to  be  united  by  the  affinity  of  aggregation , the 
cohesive  affinity , or  cohesion. 

8.  This  attraction  preserves  the  form,  and  modifies  the  texture  of 

solids,  gives  a spherical  figure  to  fluids,  causes  the  adhesion  of  sur- 
faces, and  influences  the  mechanical  characters  of  bodies.  Its  force 
is  exerted  with  the  greatest  intensity  in  solids  ;t  in  liquids  it  acts  with 
much  less  energy  ; and  in  aeriform  bodies  it  is  doubtful  if  it  exists  at 
, 

* From  a privative,  and  Teprsir  to  cut. 

t The  force  of  cohesion  in  solids  is  measured  by  the  weight  necessary  to  break  them, 
or  rather  to  pull  them  asunder. 


Chemical  Attraction — Solution. 


3 


all.  Of  this,  water  offers  a good  example  in  its  different  states  of  Sect.  1. 
ice,  water,  and  steam. 

9.  To  cohesion  is  owing  the  spherical  form  which  liquids  assume,  its  effects 
when  suffered  to  form  drops  ; as  also  their  property  of  remaining  in  liquids, 
heaped  above  the  brims  of  the  vessels  that  contain  them.  The  force 

of  cohesion  varies  in  different  liquids  and  hence  the  size  of  their 
drops  must  vary. 

10.  When  attraction  operates  upon  dissimilar  particles,  and  pro-  Heteroge- 
duces  their  union,  it  gives  rise  to  new  and  infinitely  varied,  produc-  chemical 
tions.  It  is  this  kind  of  attraction  which  is  distinguished  as  hetero-  attraction. 
geneous  ; it  is  also  called  chemical  attraction,  or  affinity. 

11.  The  results  of  attraction,  as  relating  to  the  texture  and  forms  Results, 
of  matter,  are  influenced  by  the  circumstances  under  which  it  has 
taken  place.  Sometimes  the  particles  are,  as  it  were  indiscriminately 
collected  ; and  at  others  they  are  beautifully  arranged,  giving  rise 

to  regular  and  determinate  figures. 

12.  The  regular  polyhedral  solids  thus  resulting  from  the  influence  Crystals, 
of  attraction  upon  certain  kinds  of  matter,  are  usually  called  crystals;® 

and  the  bodies  are  said  to  be  susceptible  of  crystallization. 

13.  To  enable  the  particles  of  bodies  to  assume  that  regular  form  Conditions 
which  crystals  exhibit,  they  must  have  freedom  of  motion  ; and  ac-  f^ationTn" 
cordingly  the  first  step  towards  obtaining  a body  in  its  crystalline  general, 
form,  is  usually  to  confer  upon  it  either  the  liquid  or  aeriform  state. 

This  is  effected  by  solution,  or  by  exposure  to  heat. 

14.  The  term  solution , is  applied  to  a very  extensive  class  of  phe-  Solution, 
nomena.  When  a solid  disappears  in  a liquid,  we  have  an  example 

of  solution.  The  expression  is  applied  both  to  the  act  of  combina- 
tion, and  to  the  result  of  the  process.  Solution  is  always  the  result 
of  an  attraction  or  affinity,  between  the  fluid  and  the  solid  which  is 
acted  upon,  feeble  it  is  true,  yet  sufficient  in  force  to  overcome  the 
cohesion  of  the  solid.  The  affinity  continues  to  act  until  at  length  a 
certain  point  is  attained,  where  the  affinity  of  the  solid  and  fluid  for 
each  other  is  overbalanced  by  the  cohesion  of  the  solid,  and  the  solu- 
tion cannot  be  carried  farther.  This  point  is  called  saturation , and  Saturation, 
the  fluid  obtained  is  termed  a saturated  solution. 

15.  The  particles  of  the  solid  may  be  regarded  as  disposed  at  regular  How  the 
distances  throughout  the  fluid  ; and  if  the  quantity  of  solvent  be  con- particles 
siderable,  the  particles  will  be  too  far  asunder  to  exert  reciprocal 
attraction;  in  other  words,  they  will  be  more  powerfully  attracted 

by  the  solvent  than  by  each  other.  If  we  now  slowly  get  rid  of  a 
portion  of  the  solvent,  the  solid  particles  will  gradually  approach 
each  other,  and  they  will  aggregate  according  to  certain  laws,  pro- 
ducing a regular  form. 

18.  There  are  two  other  great  and  general  objects  to  be  gained  by 
solution,  which  render  it  a process  Gf  constant  occurrence  in  the  la-  soiution. 
boratory.  The  first  is  that  of  preparing  substances  for  the  exertion  of 
chemical  action.  The  second  is  that  of  separating  one  substance 
from  another  ; this  being  continually  effected  by  the  use  of  such 
fluids  as  have  a solvent  power  over  one  or  more  of  the  substances 


From  K Qvcrjcdlog,  Ice. 


4 


* Attraction — Crystallization. 


Chap,  i.  present.  Water  is  the  great  solvent  whose  aid  is  first  to  be  called 
in  ; others  are  to  be  resorted  to  only  when  that  is  insufficient.  So 
general  and  important  is  its  use,  that  in  speaking  simply  of  the  solu- 
bility of  a body,  water  is  always  understood  to  be  referred  to.*1 
Evapora-  17.  To  recover  a salt  from  its  solution,  if  its  solubility  does  notvary 
tion.  with  the  temperature  of  the  solvent,  as  in  the  instance  of  common 
salt,  it  is  necessary  to  expel  a portion  of  the  fluid  by  heat.  This 
The  figure  constitutes  the  process  of  evaporation .t  The  regularity  of  the  figure 
influenced  (12)  obtained  will  be  influenced  by  the  rapidity  of  the  evaporation; 
oT  evapora-  ^ Process  be  slowly  conducted,  the  particles  unite  with  great  re- 
flon.  gularity ; if  hurried,  the  crystals  are  irregular  and  confused.  In 
common  cases  the  evaporation  may  be  continued  till  a pellicle  forms 
Time  for  upon  the  surface  of  the  solution.  The  formation  of  a superficial 
slopping  pellicle  is  the  common  criterion  of  the  fitness  of  a solution  for  crvs- 
vaporatioo.  ta^‘zation  ; but  where  the  object  is  to  obtain  very  regular  and  very 
large  crystals,  the  evaporation  must  be  much  slower,  and  carried  to 
much  less  extent ; even  spontaneous  evaporation,  or  that  which 
takes  place  at  common  temperatures,  must  be  resorted  to. 

Crystals  18*  There  are  certain  bodies  which  may  be  dissolved  or  liquefied 
formed  by  by  heat,  and  during  slow  cooling,  may  be  made  to  crystallize.  This 
fusion.  js  case  \Vith  many  of  the  metals,  with  spermaceti,  sulphur,  &c. 

Some  other  substances,  when  heated,  readily  assume  the  state  of 
vapour  or  are  sublimed , and  during  condensation,  present  regular 
crystalline  forms  ; such  as  iodine,  benzoic  acid,  camphor,  &c. : and 
crystals  of  snow  are  produced  by  the  condensation  and  cooling  of 
aqueous  vapour. 

Cry stalli - 19*  Some  substances  are  so  easily  decomposed  by  heat,  and  at 

zation  of  the  same  time  retain  water  with  such  avidity,  that  it  is  impossible  to 
wUhosecom-  crystallize  them  by  any  of  the  above  processes ; in  these  cases  crys- 
position  is  tallization  may  sometimes  be  effected  by  placing  the  solution  under 
feeble.  

Solubility  how  * The  solubility  of  a body  may  be  tried  by  suspending  a piece  of  it  in  a glass  of  clean 
tried.  undisturbed  water;  if  it  be  soluble  a descending  current  will  be  seen  to  fall  from  it, 

and  be  visible  upon  looking  through  the  water  horizontally.  If  it  fall  rapidly  and  in 
dense  strire,  it  will  indicate  rapid  Solubility,  and  the  formation  of  a dense  solution  ; if 
it  fall  in  a very  narrow  stream,  it  will  indicate  only  moderate  or  slight  solubility;  and 
by  its  descending  rapidly  or  in  a slow  broad  stream,  or  by  resting  about  the  substance, 
a judgment  may  be  made  of  the  comparative  density  of  the  solution  produced.  If  no 
descending  current  appear,  nor  any  fluid  round  the  substance  of  a refractive  power  or 
colour  different  to  that  of  the  water,  then  the  body  must  be  very  nearly  if  not  quite  inso- 
luble at  common  temperatures. 

If  the  suhstance  appear  to  be  insoluble,  or  if  it  be  necessary  to  know  whether  it  be 
soluble  in  alcohol,  ether,  oils,  or  any  other  body,  for  the  purpose  of  selecting  a solvent 
from  among  them,  a portion  should  be  pulverized  finely,  and  introduced  into  a small 
tube  with  a li»  tie  of  the  fluid  to  he  tried,  and  heated;  if  the  substance  disappear,  it  is 
of  course  soluble.  But  if  it  be  supposed  to  be  a mixed  body,  and  partly  soluble, 
though  not  altogether  so,  then  the  presumed  solution  should  he  poured  from  the  tube 
into  an  earthenware  or  platinum  capsule,  and  evaporated  carefully  and  slowly;  if  any 
suhstance  remain,  it  of  course  indicates  a degree  of  solubility.  F.  1G8. 

A solution  saturated  when  cold,  may  be  often  obtained  much  more  speedily  by  the 
nanine  * cow  heat,  as  by  boiling  the  suhstance  with  water,  leaving  it  to  cool,  and  afterwards 

saturated  »olu-  filtering  it,  when  a saturated  solution  will  be  at  once  obtained.  If  the  solution  while 
ti<m  cooling  deposits  any  portion  of  the  solid,  it  proves  the  saturation,  if  it  does  not,  there 

is  reason  to  doubt  it,  and  heat  with  more  of  the  solid  substance/ in  powder  should 
again  be  applied.  The  solution  may  also  be  tested  while  hot  by  dipping  into  it  a glass 
rod,  and  thus  transferring  a drop  to  a cold  glass  plate  ; if  crystals  or  solid  substance 
appear  in  a few  moments,  the  solution  will  be  saturated  when  cold.  Sometimes  this 
effect  will  not  take  place  until  the  drop  is  stirred.  F. 

t Performed  in  shallow  vessels  exposing  a large  surface  of  the  liquid. 


Basic  and  Constitutional  Water. 


5 


the  receiver  of  an  air-pump,  over  the  surface  of  sulphuric  acid,  and  Sect,  i. 
exhausting  the  air  ; the  acid,  by  absorbing  the  vapour  as  it  rises, 
causes  rapid  evaporation. 

20.  In  the  act  of  separating  from  the  water  in  which  they  were  Water  of 
dissolved,  the  crystals  of  almost  all  salts  carry  with  them  a quantity  Jl^talliza- 
of  water.  It  is  termed  their  ivater  of  crystallization , the  quantity  of 

which  is  very  variable  in  different  saline  bodies,  but  it  is  uniform  in 
the  same  salt. 

21.  The  hardness,  brilliancy,  and  transparency  of  crystals,  often 

depend  upon  their  containing  this  water,  which  sometimes  exists  in 
them  in  large  quantities.  Thus,  sulphate  of  soda,  in  the  state  of 
crystals,  contains  more  than  half  its  weight.  Gypsum,  in  its  crys- 
tallized form,  contains  about  20  per  cent,  of  water,  which  it  loses  at  a 
red  heat,  and  the  crystals  crumble  down  into  the  white  powder  called 
Plaster  of  Paris.  Some  salts  part  with  it  by  simple  exposure  to  dry  ^e®c°Jeas^d 
air,  when  they  are  said  to  effloresce  ; but  there  are  other  salts  which  del^ues- 
deliquesce , or  attract  water  from  the  atmosphere. # cence. 

22.  The  water  of  crystallization  is  retained  by  a very  feeble  affi- 
nity, as  is  proved  by  the  facility  with  which  such  water  is  separated 
from  the  saline  matter  by  a moderate  heat,  or  by  exposure  to  the 
vacuum  of  an  air-pump  at  common  temperatures.  A portion  of  the 
water  is  sometimes  retained  with  such  obstinacy,  that  it  cannot  be 
expelled  by  a temperature  short  of  that  at  which  the  salt  is  to- 
tally decomposed.  This  water  is  considered  to  act  the  part  of  a Basic  wa- 
base,  and  is  called  basic  water.  From  the  observations  of  Gra-ter> 
ham,f  the  water  thus  retained  does  not  always  appear  to  act  this 

part,  but  to  be  in  a peculiar  state  of  combination.  This  he  calls  con- 
stitutional water ; being  that  which  is  essential  to  the  existence  of  Constitu- 
tive salt.  It  differs  from  basic  water,  by  not  being  removed  even  byjg0^  wa' 
the  most  powerful  alkalies,  but  is  readily  removed,  and  its  place  as- 
sumed, by  certain  anhydrous  salts.  The  character  of  water  in  these 
different  states  of  combination  will  be  understood  from  the  following 
example.  Crystals  of  phosphate  of  soda  are  composed  of  1 propor- 
tion phosphoric  acid,  2 soda,  and  25  water.  At  the  temperature  of 
212°,  24  proportions  of  the  water  are  expelled  ; but  the  25th  propor- 
tion is  retained,  and  a red  heat  is  required  for  its  complete  separation. 

By  the  loss  of  the  24  proportions  the  crystalline  form  and  texture  of 
the  salt  are  destroyed,  but  the  residual  mass  has  all  the  properties  of 
the  common  phosphate  ; whereas,  by  the  loss  of  the  25th  proportion, 
an  entirely  different  salt,  the  pyrophosphate  of  soda,  is  produced. 

23.  In  some  cases  the  proportion  of  water  is  removed  by  an  equi-  Water  re- 
valeht  of  any  base  that  supplies  its  place  in  the  compound  ; in  others  moyed> 

it  is  not  affected  by  bases,  but  may  be  removed  by  certain  anhydrous 
salts  which  occupy  its  place,  and  give  rise  to  the  formation  of  double 
salts.  The  former,  as  acting  the  part  of  a base,  is  the  basic  water ; 
the  latter,  as  influencing  the  constitution  of  a salt,  is  the  constitu- 
tional water. 

24.  The  difference  is  denoted  in  symbols,  by  writing  the  basic  Denoted  by 

. ’ symbols. 

* Those  crystals  which  effloresce  by  exposure  to  air,  may  often  be  conveniently  pre- 
served, by  slightly  oiihig  their  surfaces.  The  best  method  is  to  soak  the  crystals  in 
oil  for  a few  hours.,  and  then  to  wipe  them  and  put  them  up  in  bottles. 

t Phil.  Trans.  Edin. , xii.  297. 


6 


Chap.  I. 


Decrepita- 

tion. 


Watery  fu 
sion. 

Crystal- 

lization 

promoted 


By  a nu- 
cleus. 


Method  of 
obtaining 
perfect 
crystals. 


Crystal- 
lization af- 
fected by 
circum- 
stances, 


By  pres- 
sure. 


Attraction — Crystallization. 

water,  as  is  the  case  with  all  bases,  on  the  left  side  of  the  acid  with 
which  it  is  combined,  and  the  constitutional  water  on  the  right. 
Hence  the  symbol  of  the  crystals  of  phosphate  of  soda  is  2NaO. 
HO,  P05+24Aq. 

25.  Salts,  in  crystallizing,  frequently  enclose  mechanically  within 
their  texture  particles  of  water,  by  the  expansion  of  which,  when 
heated,  the  salt  is  burst  with  a crackling  noise  into  smaller  frag- 
ments. This  phenomenon  is  called  decrepitation.  Those  crystals 
in  which  the  water  of  crystallization  is  so  abundant,  as  to  liquefy 
them  when  its  temperature  is  raised,  are  sometimes  said  to  undergo 
the  toatery  fusion. 

26.  Some  salts,  in  consequence  probably  of  their  strong  attraction 
for  the  water  that  retains  them  in  solution,  cannot  be  brought  to  crys- 
tallize in  the  ordinary  way.  In  such  cases,  crystallization  may  be 
effected  by  the  addition  of  substances  having  a strong  affinity  for  wa- 
ter, by  which  its  attraction  for  the  dissolved  matters  is  weakened; 
thus  alcohol,  added  to  certain  aqueous  saline  solutions,  (as  solution 
of  nitre,)  produces  a separation  of  crystals,  but  they  are  generally 
small  and  indistinct. 

27.  Crystallization  is  accelerated  by  introducing  into  the  solution 
a nucleus,  or  solid  body,  upon  which  the  process  begins  ; and  manu- 
facturers often  avail  themselves  of  this  circumstance.  Thus  we  see 
sugar-candy  crystallized  upon  strings,  and  verdigris  upon  sticks. 
There  are  case^in  which  it  is  particularly  advantageous  to  put  a few 
crystals  of  the  dissolved  salt  into  the  solution,  which  soon  cause  a 
crop  of  fresli  crystals.  In  some  instances,  if  there  be  two  salts  in 
solution,  that  will  most  readily  separate  of  which  the  crystals  have 
been  introduced. 

28.  By  placing  a crystal  of  the  same  nature  in  a saturated  solu- 
tion of  a salt,  and  turning  it  daily,  so  that  the  different  sides  shall 
be  successively  exposed  to  the  liquid,  very  large  and  perfect  crystals 
may  be  obtained. 

29.  When  two  salts  of  different  solubilities  are  present  in  the 
same  solution,  they  often  may  be  separated  by  crystallization,  that 
which  is  least  soluble  constituting  the  earlier  crop  of  crystals. 

30.  Sometimes  crystallization  is  not  effectual  for  the  separation  of 
salts.  When  the  sulphates  of  iron  and  copper  are  in  solution  toge- 
ther, crystals  will  be  obtained  resembling  those  of  sulphate  of  iron, 
but  with  very  variable  proportions  of  sulphate  of  copper  in  them,  the 
latter  salt  being  at  times  present  in  great  quantity  ; on  other  occa- 
sions triple  salts  arc  formed.  F.  254. 

31.  The  pressure  of  the  atmosphere  has  been  said  to  have  consi- 
derable influence  on  crystallization.  Thus  a concentrated  solution 
of  sulphate  of  soda  (Glauber’s  salt),  excluded  from  the  air  while  hot, 
does  not  crystallize  on  cooling;  but  will  generally  crystallize  when 
the  air  is  admitted.*  The  theory  of  this  phenomenon  is  not  very  ap- 


*The  best  method  of  exhibiting  this,  is  to  place  several  pounds  of  Glauber’s  salt  in 
a suitable  vessel,  and  to  pour  upon  it  two  parts  of  water  to  three  of  salt;  boil  it,  and 
while  hot  strain  the  solution  through  a coarse  cloth,  into  a tall,  wide,  thin  glass  jar, 
previously  warmed  ; over  the  mouth  of  the  jar  a piece  of  wet  bladder  is  to  be  securely 
tied,  and  the  whole  left  to  cool.  When  quite  cold,  a puncture  of  the  bladder  with  the 
point  of  a knife  will  often  be  followed  by  crystallization  of  the  salt — if  it  should  not 
commence,  the  introduction  of  a fragment  of  the  salt  will  be  required.  The  tempera- 


Primitive  Forms. 


1 


parent.  It  does  not  depend  upon  atmospheric  pressure,  for  the 
solution  may  be  cooled  in  open  vessels,  without  becoming  solid,  pro- 
vided its  surface  be  covered  with  a thin  film  of  oil ; and  Turner 
succeeded  with  the  same  experiment  without  the  use  of  oil,  by  caus- 
ing the  air  of  the  vessel  to  communicate  with  the  atmosphere  by 
means  of  a narrow  tube.  It  appears  from  some  experiments  of 
Graham,^  that  the  influence  of  the  air  may  be  ascribed  to  its  uniting 
chemically  with  water  ; for  he  has  proved  that  gases  which  are  more 
freely  absorbed  than  atmospheric  air,  act  more  rapidly  in  producing 
crystallization. 

32.  The  presence  of  light  also  influences  the  process  of  crystalli- 
zation. Thus  we  see  the  crystals  collected  in  camphor  bottles  in 
druggists’  windows  always  most  copious  upon  the  surface  exposed  to 
light ; and  if  we  place  a solution  of  nitre  in  a room  which  has  the 
light  admitted  only  through  a small  hole  in  the  window  shutter, 
crystals  will  form  most  abundantly  upon  the  side  of  the  basin  most 
exposed  to  the  aperture  through  which  the  light  enters,  and  often  the 
whole  mass  of  crystals  will  turn  towards  it.  Many  saline  solutions 
form  arborescent  crystalline  pellicles,  when  left  to  spontaneous  eva- 
poration, which  slowly  travel  up  the  sides  of  the  basin,  and  gradually 
proceed  down  upon  the  outside  ;t  this  process  also  always  begins  on 
the  side  nearest  the  light,  and  is  often  confined  to  it 

33.  It  is  commonly  observed,  that  crystallized  bodies,  affect  one 
form  in  preference  to  others.  The  fluor  spar  of  Derbyshire  crystal- 
lizes in  cubes  : so  does  common  salt.  Nitre  assumes  the  form  of  a 
six-sided  prism,  and  sulphate  of  magnesia  that  of  a four^sfded  prism. 
These  forms  are  liable  to  vary.  Fluor  spar  and  salt  crystallize 
sometimes  in  the  form  of  octohedrons  ; and  there  are  so  many  forms  of 
carbonate  of  lime,  that  it  is  difficult  to  select  that  which  most  com- 
monly occurs. 

34.  Rome  de  Lisle  referred  these  variations  of  form  to  certain 
truncations  of  an  invariable  primitive  nucleus;  and  Gahn  afterwards 
observed,  that  when  a piece  of  calcareous  spar  was  carefully  broken, 
all  its  particles  were  of  arhomboidal  figure.  This  induced  Bergman 
to  suspect  the  existence  of  a primitive  nucleus  in  all  crystallized  bo- 
dies.! This  subject  was  more  extensively  prosecuted  by  Haiiy. 
He  determined  the  primary  forms  of  minerals,  and  showed  how  sec- 
ondary forms  could  be  derived  from  them  by  simple  laws  of  decre- 
ment.^ 

35.  Haiiy  obtained  his  primary  forms  by  mechanical  division: 
thus  hy  the  skilful  division  of  a six-sided  prism  of  calcareous  spar,  he 
reduced  it  to  a rhomb,  precisely  resembling  that  which  is  known 
under  the  name  of  Iceland  crystal.  Other  forms  of  calcareous  spar 
were  subjected  to  the  same  operation  ; and,  however  different  at  the 
outset,  finally  agreed  in  yielding,  as  the  last  product,  a rhomboidal  solid. 


ture  of  the  jar  will  rise  during  the  change  from  the  fluid  to  the  solid  state.  If  a glo- 
bular vessel,  as  a matrass,  is  employed,  it  will  often  be  broken  during  the  crystalliza- 
tion. The  crystallization  will  olten  take  place  on  slight  agitation  without  the  access 
of  air. 

* Phil.  Trans.  Edin.  1828-  See  also  N.  Edin.  Jour.  xiii.  309. 

+ This  may  be  prevented  by  smearing  the  edge  of  the  vessel  with  oil. 

t Phys.  and  Cherti.  Essays,  Yol.  II.  p.  1.  § TraiU  de  Min.  Paris : 1801. 


Sect.  1. 


By  light. 


Assume 
one  form 
rather  than 
another. 


Primitive 

nuclei. 


Hatty’s 

primitive 

forms. 


8 


Attraction — Crystallization. 


Chap.  I. 


Daniell’s 

method. 


Wollas- 
ton’s theo- 
ry- 


Fig.  7. 


It  was  discovered  also  by  Haiiy,  that  if  we  take  a crystal  of  another 
kind  (the  cubic  fluor  spar,  Derbyshire  spar,  for  instance,)  the  nucleus 
obtained  by  its  mechanical  division,  will  have  a different  figure,  viz. 
an  octohedron.* 

36.  A method  of  developing  the  structure  of  crystals,  has  been 
described  by  Daniell.t  It  consists  in  exposing  any  moderately 
soluble  salt  to  the  slow  and  regu- 
lated action  of  a solvent.  Thus  if  a 
lump  of  alum  is  placed  in  water,  after 
some  days,  oetohedrons  and  sections  of 
octohedrons  will  be  seen  in  relief  upon 
its  lower  part.  (Fig.  7.)  The  crystal- 
line forms  of  metals  may  be  in  a similar 
manner  developed  by  immersion  in  di- 
lute acids. 

37.  From  the  imperfect  explanation  of  many  of  the  appearances  of 
crystals,  afforded  by  the  theory  of  Haiiy,  Wollaston  proposed  to 
consider  the  primitive  particles  as  spheres,  which,  by  mutual  attrac- 
tion, have  assumed  that  arrangement  which  brings  them  as  near  as 
possible  to  each  other.  By  the  due  application  of  spheres  to  each 
other,  he  has  shown  that  a variety  of  crystalline  forms  may  be  pro- 
duced.f 


♦The  primary  forms  of  HaOy  are  reducible  to  six;  the  paralleiopiped,  fig.  1.  which 
includes  the  cube,  the  rhomb,  and  all  the  solids  which  are  terminated  by  six  faces, 
parallel  two  and  two ; the  tetrahedron,  fig.  2 ; the  octohedron,  fig.  3 ; the  regular  hexahe- 


Fig.  1.  Fig.  2.  I ig.  3. 


drnl  prism,  fig  4 ; the  dodecahedron  with  equal  and  similar  rhomltoidal  planes,  fig.  5 ; 
and  the  dodecahedron  with  triangular  planes,  fig.  6. 


Fig.  4.  Fig.  6 Fig.  6. 


The  instruments  used  for.mcasnring  the  angles  at  which  the  plaoes  of  crystals  meet, 
or  incline  to  each  other,  are  called  goniometers.  For  the  description  of  these  and  the 
method  of  using  them  see  Cleareland’s  Mineralogy,  chap.  2d.  (edit.  IS22-)  Brooke's 
Crystallography,  p.  25. 
t Jour,  of  Sd.  and  Arls,  I.  24. 

t Philos.  Trans.  1813,  p.  51.  Other  and  very  different  views  of  the  subject  of  pri- 
mitive forms,  have  been  taken  by  Brooke.  Mohs  and  others.  For  more  ample 
information  on  this  subject  consult  the  “ Familiar  introduction  to  Crystallogra- 
phy, by  H.  J.  Brooke”;  Mohs’  Treatise  on  Mineralogy ; M Elements  of  Crystallo- 
graphy,'' hy  G.  Rose;  or  Whewell's  Essay  in  the  Phil.  Trans.  Lmd..  1825  : “ She- 
s'  Mineralogy ,"  aud  " A System  of  Mineralogy  including  an  (Mended  Treatise  on 
Crystallography ,M  by  James  D.  Dana,  M.  D.  New  Haven  : 1837. 


9 


Simple  and  Compound  Forms. 

38.  The  forms  of  crystals  may  be  divided  into  simple  and  com-  Sect-  l 
pound;  a simple  form  has  all  its  faces  equal  and  similar  to  each  simple  and 
other,  while  a compound  form  is  bounded  by  at  least  two  different  compound 
classes  of  faces;  thus  figs.  8,  9,  10  are  simple  forms.  Figs.  11,  12,  furms‘ 


Fig.  8.  Fig.  9.  Fig.  10. 


Fig.  11.  Fig.  12.  Fig.  13, 


six  octagonal,  and  twelve  quadratic.  The  lines  round  which  the  dif"Axes 
ferent  parts  of  crystals  are  grouped,  are  called  crystalline  axes.  It 
will  be  observed  that  in  the  figures  8,  9,  10,  three  right  lines,  which 
are  equal  in  length  and  perpendicular  to  each  other,  may  pass 
through  the  centre  of  the  crystal ; in  fig.  8 by  joining  the  opposite 
angles,  in  fig.  9 by  joining  the  centres  of  the  opposite  faces,  and  in 
fig.  10  by  connecting  the  opposite  angles  formed  by  the  meeting  of 
four  edges.  These  forms  are  thus  connected  by  having  the  same 
axes  of  crystallization,  and  proceeding  from  these  three  equal  and 
rectangular  axes,  either  the  octohedron,  the  cube,  or  the  rhombic 
dodecahedron  may  be  constructed,  the  resulting  form  depending  solely 
on  the  law  according  to  which  planes  are  symmetrically  arranged 
around  the  axes. 

39.  From  the  law  that  every  plane  shall  pass  through  an  extre-  Laws. 
mity  of  each  axis , results  the  octohedron  fig.  8-  This  law  limits  the 
number  of  faces  to  eight,  and  as  these  intersect  in  the  lines  joining 

the  extremities  of  the  axes,  each  face  is  an  equilateral  triangle,  and 
the  resulting  form  is  the  regular  octohedron.  From  the  law  that 
each  plane  shall  pass  through  an  extremity  of  one  axis  and  be  paral- 
lel to  the  other  two>  results  the  cube  fig.  9.  As  each  axis  has  two 
extremities,  only  six  planes  can  be  grouped  around  them,  and  by 
their  intersection  the  hexahedron,  or  cube,  is  produced.  In  a similar 
manner  may  the  rhombic  dodecahedron,  fig.  10,  be  shown  to  be 
formed  according  to  the  law  that  each  plane  shall  pass  through  the 
extremities  of  two  axes , and  be  parallel  to  the  third. 

40.  Simple  forms  thus  associated  by  being  reducible  from  the  same 

2 


10 


Attraction — Crystallization. 


ChaP-  i-  axes,  constitute  what  is  termed  a system  of  crystallization . Thus  the 
Systems  of  octohedron,  cube,  and  rhombic  dodecahedron  are  three  forms  of  the 
crystaUiza-  octo^c<^ra^  or  regular  system.  Such  forms  are  connected  still  more 
intimately  by  the  remarkable  fact,  that  any  substance  which  in  crys- 
tallizing assumes  one  form  of  a system,  may,  and  frequently  does,  as- 
sume other  forms  belonging  to  that  system ; and  what  is  still  more 
remarkable,  the  same  substance  is  not  only  capable  of  assuming  dif- 
ferent forms  of  the  same  system,  but  during  the  act  of  crystallization, 
the  faces  of  two,  three,  four,  and  in  some  cases  even  more,  of  these 
forms  are  simultaneously  developed,  whereby  compound  crystals  of 
the  greatest  diversity  of  form  and  appearance  are  produced.* 

41.  A knowledge  of  all  the  simple  forms  of  a system,  as  being 
those  in  which  the  same  substance  may  occur,  and  which  alone  can 
give  rise  to  compound  crystals,  is  highly  important.  Haiiy  first 
proved  the  existence  of  a mathematical  connexion  between  them ; 
but  we  are  indebted  (o  Weiss,  of  Berlin,  for  the  distinction 
of  the  system  of  crystallization.  He  has  shown  that  all  crystalline 
forms  may  be  brought  under  one  of  the  six  following  systems,  which 
may  be  distinguished  as 

1.  The  octohedrnl,  or  regular  system.  4..  The  oblique  prismatic  system. 

2.  The  square  prismatic  system.  5.  The  square  prismatic  system. 

3.  The  right  prismatic  system.  6.  The  rhombohedral  system. 

42.  The  octohedral  system  is  characterized  by  the  three  equal 
and  rectangular  axes  already  described.  If  we  suppose  that  two  of 
the  axes  are  horizontal,  and  the  third  vertical  (figs.  8,  9,  and  10), 

?vc«i°«mdral  the  ^aw  symmetry  is  such,  that  if  a face  of  a crystal  be  observed 
to  bear  a certain  relation  to  one  of  the  horizontal  axes,  other  faces 
must  fulfil  the  same  condition  to  the  other  equal  axes.  From  the 
perfect  symmetry  in  the  different  parts  of  the  crystal,  this  group  is 
often  called  the  regular  system  of  crystallization.  It  consists  of  but 
few  simple  forms,  the  number  being  necessarily  limited  to  the  num- 
ber of  different  ways  in  which  a plane  can  intersect  the  three  axes. 
These  are  only  seven. 

Number  of  1.  The  plane  may  cut  each  at  an  equal  distance  from  the  centre, 
as  in  the  octohedron  (fig.  8). 

2.  The  plane  may  cut  two  axes  at  an  equal,  and  the  third  at  a 
greater  distance  from  the  centre.  The  resulting-  form  is  called 
the  Triakisoctohedron. 

3.  The  plane  may  cut  two  axes  at  an  equal,  and  the  third  at  a less 
distance  from  the  centre.  The  resulting  form  is  the  Ikositetra- 
hedron. 

4.  The  plane  may  cut  all  three  axes  unequally.  The  resulting  form 
is  the  Herakisoctohedron. 

5.  The  plane  may  cut  two  axes  at  unequal  distances  from  the  cen- 
tre, and  be  parallel  to  the  third.  The  resulting  crystal  is  the 
Tetrakishexahedron. 

6.  The  plane  may  cut  two  axes  in  points  equally  distant  from  the 


system. 


forms. 


* Thus  alum  may  crystallize  in  the  form  of  a cube,  or  •'ctohedron.  but  the  compound 
crystal,  fig.  II,  is  more  common,  where  the  faces  of  the  cube  truncate  the  angles  of 
the  octohedron.  Fig.  12,  is  another  form  of  the  alum,  where,  in  addition  to  the  octo- 
hedron, the  faces  of  the  rhombic  dodecahedron  are  also  developed.  Fig.  13  represents 
a combination  of  all  three  forms. 


Systems  of  Crystallization. 


11 


The  form  is  the  rhombic  Sect. 


centre,  and  be  parallel  to  the  third, 
dodecahedron  (fig.  10). 

7.  The  plane  may  cut  one  axis,  and  be  parallel  to  the  other  two. 

The  form  is  the  cube  or  hexahedron  (fig.  9). 

Of  these  forms,  1,  6,  and  7 are  of  frequent  occurrence  ; the  others 
are  usually  found  in  combination. 

43.  The  square  prismatic  system.  The  forms  of  this  system  Square 
are  also  characterized  by  three  axes  which  intersect  each  other  at  prismatic 
right  angles ; but  they  differ  from  those  of  the  first  system  by  two  system’ 
only  out  of  the  three,  laeing  equal.  Let 
the  third  axis  be  supposed  in  a vertical  po- 
sition (fig.  14),  the  octohedron  formed 
is  either  longer  or  shorter  in  the  direction 
of  this  axis,  than  in  that  of  its  horizontal’ 
axis.  These  octohedrons  may  be  com- 
pared to  a double  four  sided  pyramid  on  a 
square  base.  The  parts  about  the  base 
are  similar  to  each  other,  but  differ  from  those  about  its  upper  or 
lower  extremity;  and  this  character  distinguishes  the  system. 

44.  The  right  prismatic  system.  The  crystals  of  this  system  are  Right  pris- 


Fig.  14, 


Fig.  15. 


Fig.  16. 


Fig.  17. 


malic  sys- 
tem. 


like  the  preceding,  characterized  by  three  rectangular  axes,  and 
are  distinguished  from  both  by  no  two  of  these  axes  being  equal. 


45.  The  oblique  prismatic  system.  The  crys- 
tals of  this  system  (fig.  18),  differ  from  those 
of  the  last  by  the  front  and  back  parts  being 
dissimilar.  This  is  owing  to  two  of  the  axes 
intersecting  each  other  obliquely,  while  the  third 
still  remains  perpendicular  to  both. 


Fig.  18. 


Oblique. 


46.  The  double  oblique  system  is  readily  re- 
cognized by  the  complete  absence  of  all  sym- 
metry in  its  crystalline  forms.  This  results 
from  all  three  axes  intersecting  each  other 
obliquely ; owing  to  which  the  left  and  right 
sides,  as  well  as  the  back  and  front,  are  of 
different  crystalline  values.  Hence  no  two  faces 
are  connected  except  those  which  are  parallel, 
and  all  symmetry  of  form  disappears. 


Fig.  19. 


Double  ob- 
lique. 


12 


Attraction — Isomorphism. 


Chap.  I. 

Rhombohe- 

dral. 


Fig.  20. 


Discovery 
of  Mitscher- 
lich. 


Isomorph- 

ism. 


Crystalli- 
zation and 
separation 
of  isomor- 
phous  sub- 
staucos. 


Advantages 
from  iso- 
morphism, 


47.  The  rhombokedral  system.  The  forms  of  this  system  are,  like 
the  octohedral,  characterized  by  three  equal  and  si- 
milar axes  ; but  these  axes  intersect  each  other  at 
equal,  but  not  at  right  angles.  Its  most  simple 
form  is  the  rhombohedron  (fig.  20),  which  is 
bounded  by  six  equal  and  similar  rhombic  faces. 

The  axes  are  obtained  by  joining  the  centre  of  the 
opposite  faces.* 

48.  In  the  year  1819,  a discovery,  extremely  important  both  to 
mineralogy  and  chemistry,  was  made  by  Mitscherlich  of  Berlin, 
relative  to  the  connexion  between  the  crystalline  form  and  com- 
position of  bodies.  It  appears  from  his  researches,!  that  certain 
substances  have  the  property  of  assuming  the  same  crystalline  form, 
and  may  be  substituted  for  each  other  in  combination  without  affect- 
ing the  external  character  of  the  compound.  Thus  crystals  pos- 
sessed of  the  form  and  aspect  of  alum  may  be  made  with  sulphates 
of  potassa  and  sesquioxide  of  iron,  without  a particle  of  aluminous 
earth;  and  a crystal  composed  of  selenic  acid  and  soda  will  have  a 
perfect  resemblance  to  Glauber’s  salt. 

49.  To  the  new  branch  of  science  laid  open  by  this  discovery,  the 

term  isomorphism  (from  loos  equal,  and  form)  is  applied  : 

and  those  substances  which  assume  the  same  figure,  are  said  to  be 
isomorphous.  Of  these  isomorphous  bodies,  several  distinct  groups 
have  been  described  by  Mitscherlich.! 

50.  From  the  facts  observed,  the  form  of  crystals  is  inferred  to 
depend  on  their  atomic  constitution,  and  they  at  first  induced  Mits- 
cherlich to  suspect  that  crystalline  form  is  determined  solely  by  the 
number  and  arrangement  of  atoms,  quite  independently  of  their  na- 
ture, Subsequent  observations,  however,  induced  him  to  abandon 
this  view  ; and  to  incline  to  the  opinion  that  certain  elements,  which 
are  themselves  isomorphous,  when  combined  in  the  same  manner 
with  the  same  substance,  communicate  the  same  form. 

51.  Isomorphous  substances  crystallize  together  with  great  readi- 
ness, and  are  separated  from  each  other  with  difficulty.  Thus 
a weak  solution  of  lime,  which  in  pure  water  would  be  instantly 
indicated  by  oxalate  of  ammonia,  is  very  slowly  affected  by  that  test 
when  much  sulphate  of  magnesia  is  present  and  Turner  found 
that  chloride  of  manganese  cannot  be  purified  from  lime  by  oxalate 
of  ammonia. 

The  sulphates  of  zinc  and  copper,  of  copper  and  magnesium,  of 
copper  and  nickel,  of  zinc  and  manganese,  and  of  magnesium  and 
manganese  crystallize  together,  and  have  the  same  form  as  green  vit- 
riol, without  containing  a particle  of  iron.  These  mixed  salts  may  be 
crystallized  over  and  over  again  without  the  ingredients  being  sepa- 
rated from  each  other.  T.  418. 

52.  The  tendency  of  isomorphous  bodies  to  crystallize  together, 

* For  more  minute  details  see  Turner’s  Elements , 6th  edit.  p.  409. 

t Ann.  de  Ch.  ei  dc  Phys.,  vol.  xiv.  172,  xix.  350,  and  xxiv.  264  and  366. 

t For  a table  of  isomorphous  substances  see  Johnston's  Report  on  Chemistry , 
in  vol.  1st  of  Reports  of  British  Association,  1831 — 2. 

§ Daubeny,  in  Edin.  Phil.  Jour . vii.  108- 


Chemical  Attraction.  13 

accounts  for  the  difficulty  of  purifying  mixtures  of  isomorphous  salts  Sect,  n. 
by  crystallization.  The  same  property  sets  the  chemist  on  his  guard 
against  the  occurrence  of  isomorphous  substances  in  crystallized 
minerals.  It  is  a useful  guide  in  discovering  the  atomic  constitu- 
tion of  compounds.  For  example,  from  the  composition  of  the  oxides 
of  iron,  and  the  compounds  which  this  metal  forms  with  other  bodies, 
it  is  known  that  the  sesquioxide  consists  of  two  atoms  of  iron  and 
three  atoms  of  oxygen;  and,  therefore,  it  is  inferred  that  alumina, 
which  is  isomorphous  with  sesquioxide  of  iron,  has  a similar  consti- 
tution.* 

53.  In  connexion  with  chemistry,  the  theory  of  crystallization  Connexion 
opens  a new  avenue  to  the  science,  and  frequently  enables  us  to  as- 
certain  directly,  that  which,  independent  of  such  aids,  could  only  be  with  chem- 
arrived  at  by  an  indirect  and  circuitous  route.  We  frequently  read  istry- 
the  chemical  nature  of  substances,  in  their  mechanical  forms.  In 
the  arts,  the  process  of  crystallization  is  turned  to  very  valuable 
account,  in  the  separation  and  purification  of  a variety  of  substances. 


Section  II.  Heterogeneous  Attraction , or  Affinity. 

54.  Having  considered  attraction  as  disposing  the  particles  of  bo-  Chemical 
dies  to  adhere  so  as  to  form  masses  or  aggregates ; and  in  many  in.  attraction 
stances,  to  arrange  themselves  according  to  peculiar  laws,  and  to  as- 

sume  regular  geometrical  figures — we  are  now  to  regard  this  power 
as  operating  upon  dissimilar  particles  ; as  presiding  over  the  com- 
position of  bodies  ; and  as  producing  their  chemical  varieties.  This 
is  Chemical  Attraction,  or  Affinity. 

55.  Chemical  affinity,  like  the  cohesive  attraction,  is  effective  on-  Distin- 

ly  at  insensible  distances ; but  it  is  distinguished  from  the  latter  fromhcohe- 
force,  in  being  exerted  between  the  particles  or  atoms  of  bodies  of  sive  attrac- 
different  kinds.  The  result  of  its  action  is  a new  compound,  in  tion- 
which  the  properties  of  the  components  have  either  entirely  or  part-  ^^urac- 
ly  disappeared,  and  in  which  new  qualities  are  also  apparent.  tion. 

Thus,  a piece  of  marble  is  an  aggregate  of  smaller  portions  of  marble  attach- 
ed to  one  another  by  cohesion , and  the  parts  so  attached  are  the  integrant  parti- 
cles ; each  of  which,  however  minute,  is  as  perfect  marble  as  the  mass  itself. 

But  the  integrant  particles  consist  of  two  substances,  lime  and  carbonic  acid, 
which  are  different  from  one  another  as  well  as  from  marble,  and  are  united  by 
chemical  attraction. 

The  integrant  particles  of  a body  are  therefore  aggregated  togeth- 
er by  cohesion  ; the  component  parts  are  united  by  affinity. 

56.  The  most  simple  instance  of  the  exercise  of  chemical  attrac-  Instances, 
tion  is  afforded  by  the  mixture  of  two  substances  with  one  another. 

Water  and  sulphuric  acid,  or  water  and  alcohol  combine  readily.  So 

when  potassa  is  added  to  sulphuric  acid  chemical  affinity  is  exerted, 
and  they  combine  together.  If  the  two  last  substances  are  examin- 
ed before  being  presented  to  each  other,  each  will  be  found  to  be 
distinguished  by  peculiar  properties.  The  potassa  will  convert  the 


* Plesiomorphism  (from  the  Greek  near)  is  the  term  proposed  by 

Miller  to  indicate  the  forms  of  substances  that  approximate  but  are  not  identical  ; 
such  have  been  brought  forward  by  Brooke  against  the  doctrine  of  isomorphism.  See 
his  essay,  and  the  reply  of  Whewell,  in  Philos.  Mag.  and  Ann.  N.  S-  X.  161  & 401. 


14 


Attraction — Chemical. 


Chap  i. 


Neutraliza 

tion, 


Distin- 
guished 
from  satu- 
ration. 


The  com- 
pound may 
nave  dis- 
tinct pro- 
perties. 

Exp.  1. 


Exp.  2. 
Exp.  3. 

Results. 


blue  colour  of  vegetable  infusions*  to  green,  the  acid  will  turn 
them  red.  But  if  we  gradually  add  the  potassa  to  the  acid,  we  shall 
obtain  a liquid  which  will  have  neither  the  properties  of  the  potassa 
or  of  the  acid ; and  which  will  no  longer  change  the  colour  of  the 
vegetable  infusion,  and  the  taste  of  which  will  have  been  converted 
into  a bitter  one. 

57.  In  cases  of  this  kind  where  chemical  combination  takes  place, 
and  the  qualities  of  the  component  parts  of  a compound  are  no  lon- 
ger to  be  detected  in  it ; the  bodies  combined  are  said  to  neutralize 
each  other. 

58.  Neutralization  is  to  be  distinguished  from  saturation,  (14)  by 
which  we  express  those  weaker  combinations  where  there  is  no  re- 
markable alteration  of  qualities,  as  in  cases  of  solution. — Water,  for 
example,  will  dissolve  successive  portions  of  common  salt,  or  sugar, 
until  at  length  it  refuses  to  take  up  more  ; or  is  saturated;  the  so- 
lution retaining  the  saline  or  sweet  taste  and  some  other  qualities  of 
the  salt  or  sugar.  The  only  physical  quality  that  is  changed  being 
that  of  cohesion. t 

59.  In  many  cases,  the  properties  of  the  compounds  resulting 
from  chemical  affinity  differ  essentially  from  those  of  their  compo- 
nent parts,  and  a series  of  new  bodies,  possessed  of  distinct  and  pe- 
culiar characters,  is  produced. 

Thus  when  two  volumes  of  nitric  oxide  gas  (Deutoxide  of  Nitrogen)  are 
mixed  with  one  of  oxygen,  an  orange-coloured  gas  results,  very  sour,  ana  soluble 
in  wator,  wheroas,  the  gases  before  mixture  were  colourless,  tasteless,  and  insolu- 
ble in  water. 

If  into  a glass  vessel,  exhausted  of  air,  be  introduced  sulphur,  and  copper  fi- 
lings, and  heat  he  applied  so  as  to  melt  the  former,  it  will  presently  combine  with 
the  lattor. 

If  we  mix  a quantity  of  iron  filings  and  sulphur,  nnd  melt  them  in  a crucible, 
we  obtain  a brittle  mass  which  has  properties  different  from  those  of  either  of 
its  constituent  parts. 

60.  We  observe  as  the  results  of  this  attraction  between  these  sub- 
stances, 1,  that  the  substances  produced  have  not  the  intermediate 
properties  of  their  elements  but  that  they  present  new  characters , 


Te*t  liquid.  * An  infusion  of  purple  cabbage  affords  an  economical  and  convenient  liquid  for 
this  and  similar  purposes.  For  its  preparation.  <>no  or  more  red  cabbages  should  be 
cut  into  strips,  and  boiling  water  poured  upon  the  pieces,  a little  dilute  sulphuric  acid 
is  to  be  added,  and  the  whole  well  stirred  : it  is  then  to  be  covered  and  kept  hot  as 
long  as  possible,  or  if  convenient,  should  be  heated  nearly  to  boiling  for  an  hour  or 
two  in  a c »pper  or  earthen  vessel.  The  quantity  of  water  to  be  added  at  first  should 
be  sufficient  to  cover  the  cabbage,  and  the  sulphuric  acid  should  be  in  the  proportion 
of  about  half  an  ounce  of  strong  oil  of  vitriol  bv  measure  to  each  good  sized  plant. 
This  being  done,  the  lluid  should  be  separated  and  drained  off.  and  as  much  more  hot 
water  poured  on  as  will  cover  the  solid  residue,  adding  a very  little  sulphuric  acid.  The 
whole  is  to  be  closed  up,  and  suffered  to  stand  until  cooled,  and  then  the  liquid  poured 
off  and  added  to  the  former  infusion.  The  in  fusion  is  to  be  evaporated  to  one  half 
or  one  third  its  first  bulk,  poured  into  a jar,  allowed  to  settle,  and  the  clear  red  fluid 
decanted  and  preserved  in  bottles.  This  solution  will  keep  a year.  When  required 
for  use,  the  acid  of  a small  portion  of  it  should  be  neutralized  by  caustic  potassa  or 
soda,  (not  by  ammonia.)  when  it  will  assume  an  intensely  deep  blue  colour,  andwill  in 
most  cases,  require  dilution  with  twelve  or  fourteen  parts  of  water.  Faraday. 

+ Neutralizations  are  best  effected  with  the  assistance  of  heat,  especially  if  a car- 
bonate be  used,  or  if  precipitation  occur  during  the  operation.  The  carbonic  acid  in 
the  first  case  is  dissipated,  and  in  the  latter  the  combination  is  more  rapidly  and 
perfectly  effected.  Evaporating  basins  are  highly  useful  for  these  purposes, 
their  contents  being  easily  stirred,  and  the  rod  used  for  that  purpose  also  applied 
to  moisten  the  test  paper  when  required.  The  solution  to  be  neutralized  should 
not  be  very  strong,  and  the  substance  added  should  be  diluted  upon  approaching  the 
point  of  neutralization,  if  it  be  accurately  required.  F.  274. 


Change  of  Properties. 


15 


Solid  pro- 
ducts. 


Fig.  21. 


2,  that  in  the  second  experiment  much  heat  and  light  are  evolved  Sect,  n. 
during  the  mutual  action  ; 3,  that  the  substances  will  unite  in  cer- 
tain proportions  only. 

61.  In  liquids  and  gases,  similar  changes  of  properties  may  be 
exhibited,  and,  in  many  cases,  a change  of  form  or  state  results. 

Thus  the  combination  of  aeriform  bodies  produces  a solid. 

Into  a retort  (fig.  21,  a,)  introduce 
a small  quantity  of  liquid  ammonia 
(volatile  alkali,)  and  into  another  a 
little  hydrochloric  (muriatic)  acid ; in- 
sert the  beaks  of  the  retorts  into  the 
extremities  of  a glass  cylinder,  b. 

The  gases  arising  from  the  acid  and 
ammonia,  pass  into  the  cylinder  and 
unite  to  form  a new  solid  compound, 
hydrochlorate  of  ammonia  (sal  am- 
moniac.) 


Exp.  1. 


If  to  a concentrated  solution  of  hydrochlorate  of  lime,  sulphuric  acid  or  a sat- 
urated solution  of  carbonate  ofpotassa  be  gradually  added,  a white  solid  will  result. 

62.  In  other  cases  the  solids  are  converted  into  aeriform  matter, 
of  which  the  combustion  of  gunpowder  is  a familiar  instance. — Gas- 
es also,  form  a liquid  ; as  when  olefiant  gas  is  mixed  with  chlorine. 

When  certain  liquids  are  presented  to  each  other,  gases  are  the 
result,  as  when  to  two  parts  of  alcohol  we  add  one  part  of  nitric  acid, 
an  effervescence  ensues,  and  aeriform  matter  is  copiously  evolved. 

Solids  also  produce  liquids. 

Rub  together  in  a mortar  a few  crystals  of  Glauber’s  salt  with  nitrate  of  am- 
monia, the  two  solids  will  become  fluid. 

Such  operations  are  not  confined  to  art.  Nature  presents  them 
on  an  extended  scale  ; and  in  connexion  with  the  functions  of  life, 
renders  them  subservient  to  the  most  exalted  purposes. 

63.  The  new  chemical  powers  that  bodies  thus  acquire  in  conse- 
quence of  combination,  are  often  extremely  remarkable,  and  can  on- 
ly be  learned  by  experiment.  It  frequently  happens  that  inert  bodies 
produce  inert  compounds,  and  that  active  substances  remain  active 
when  combined  ; but  the  reverse  often  occurs : thus  oxygen,  sulphur, 
and  water,  in  themselves  tasteless  and  comparatively  inert,  produce 
sulphuric  acid  when  chemically  combined  ; and  potassa,  which  is  a 
powerful  caustic,  when  combined  with  sulphuric  acid,  forms  a salt* 
possessing  little  activity. 

64.  The  colours  of  bodies  are  altered  by  chemical  action. 

Into  a weak  solution  of  nitrate  of  copper,  drop  liquid  ammonia,  a rich  blue 
colour  will  be  produced.  Add  gradually,  on  the  end  of  a glass  rod,  a little  sul- 
phuric acid,  the  liquid  will  become  colourless. 

To  an  infusion  of  purple  cabbage  add  a few  drops  of  an  acid,  the  colour  will 
be  changed  to  red. — The  addition  of  liquid  potassa,  in  quantity  just  sufficient  to 
neutralize  the  acid,  will  restore  the  original  colour. 

The  addition  of  potassa  alone,  produces  a green  colour. 

Into  a small  jar  of  chlorine  gas,  confined  by  water,  introduce  a piece  of  lit- 
mus paper,  the  colour  will  be  wholly  destroyed. 

When  sulphate  of  copper  (blue  vitriol,)  and  acetate  of  lead  (sugar  of  lead) 
are  rubbed  together  in  a mortar;  the  new  compound  has  a green  colour. 

Calomel  and  potassa,  both  colourless,  when  rubbed  in  a mortar  form  a black 
compound. 


Eip.  2. 
Gaseous. 


Liquid. 

Exp. 


Changes 
produced 
by  chemi- 
cal action. 
Exp. 

Exp. 


Exp. 

Exp. 

Exp. 

Exp. 


* The  term  salt  in  chemistry  is  not  confined  to  those  substances  called  salts  in  or- 
dinary discourse. 


16 


Attraction — Chemical. 


Chap.  I. 
Exp. 

Change  of 

specific 

gravity, 


And  of 

tempera- 

ature. 


Kxp. 


Ignition. 


Rip. 


Eip. 


Chemical 
action  pro- 
moted by 
mechanical 
division, 

Exp. 


By  heat, 
Exp. 


Iodine,  whose  vapour  is  of  a violet  hue,  forms  a beautiful  red  compound  with 
" mercury,  and  a yellow  one  with  lead. 

65.  The  specific  gravity  of  bodies  is  altered  by  chemical  action. 
Two  bodies  rarely  occupy  the  same  space  after  combination  which 
they  did  separately.  In  general  their  bulk  is  diminished,  so  that  the 
specific  gravity  of  the  new  body  is  greater  than  the  mean  of  its 
components.  Thus  a mixture  of  100  equal  measures  of  water  and 
an  equal  quantity  of  sulphuric  acid  does  not  occupy  the  space  of  200 
measures,  but  considerably  less.  A similar  contraction  frequently 
attends  the  combination  of  solids.  Gases  often  experience  a re- 
markable condensation  when  they  unite.  But  there  are  exceptions. 
The  reverse  happens  in  some  metallic  compounds ; and  there  are 
examples  of  combination  between  gases  without  any  change  in  bulk. 

66.  A change  of  temperature  generally  accompanies  chemical 
action.  Caloric  is  evolved  either  when  there  is  a diminution  in  the 
bulk  of  the  combining  substances  without  a change  of  form,  or  when 
a gas  is  condensed  into  a liquid,  or  when  a liquid  becomes  solid 
(61.  Exp.  2)  ; and  as  when  water  is  poured  upon  quicklime. 

When  equal  parts  of  sulphuric  acid  and  water  are  mixed,  the  temperature  is 
so  much  increased  that  if  the  mixture  bo  made  in  a phial  about  which  tow  is 
wrapped  containing  a few  pieces  of  phosphorus,  the  phosphorus  will  be  in- 
flamed.* 

67.  Ignition  is  a frequent  attendant  upon  chemical  action, 
(59.  Exp.  2.) 

Mix,  cautiously,  a small  quantity  of  sugar  with  about  half  its  weight  of  the 
salt  called  chlorato  of  notnssa,  form  the  mixture  into  a heap  upon  a plate  of 
iron,  and  drop  upon  it  from  the  extremity  of  a glass  rod,  a little  sulphuric  acid,  it 
will  bo  inflamed. 

Drop  a small  piece  of  potassium  into  water,  or  upon  ice,  hydrogen  gas  will  be 
disengaged  and  take  fire. 

68.  As  chemical  action  takes  place  among  the  ultimate  or  con- 
stituent elements  of  bodies,  it  must  obviously  be  opposed  by  the  co- 
hesion of  their  particles,  and  chemical  attraction  is  often  prevented 
by  mechanical  aggregation. 

Introduce  a pieco  of  tho  metal  antimony  into  a jar  of  chlorine  gas,  it  will  be 
only  slowly  and  superficially  acted  upon  ; but  if  tire  mechanical  aggregation  be 
previously  diminished,  by  reducing  tiro  metal  to  powder,  it  in  that  state  rapidly 
unites  with  the  gas,  and  bums  the  instant  that  it  is  introduced. 

The  influence  of  mechanical  division  in  promoting  the  action  of 
chemical  affinity,  and  in  favouring  solution,  will  be  obvious,  if  into 
a vessel  containing  dilute  hydrochloric  acid  we  drop  a lump  of  mar- 
ble ; and  into  another  vessel  containing  the  same  acid  we  pour  an 
equal  weight  of  marble  reduced  to  powder. 

69.  The  chemical  energies  of  bodies,  are  increased  by  heat. 

To  four  ounce- measures  of  water,  at  the  temperature  of  the  atmosphere,  add 
three  ounces  of  sulphate  of  soda  in  powder,  only  part  of  the  salt  will  be  dissolv- 
ed, even  after  being  agitated  some  time.  Apply  neat,  and  the  whole  of  the  salt 
will  disappear. 

To  this  law,  however,  there  are  several  exceptions ; for  many 
salts  are  equally,  or  nearly  equally,  soluble  in  cold  as  in  hot  water ; 
as  will  be  seen  hereafter. 

The  effects  of  heat  are  sometimes  only  referable  to  the  diminution 
of  adhesion  by  expansion,  or  liquefaction  ; but  in  other  cases  they 


* As  the  phial  is  often  broken,  it  should  be  placed  upon  a plate. 


Double  Elective  Affinity. 


17 


are  peculiar  and  cmnplicated,  and  probably  concerned  in  modnying  Sect,  u. 
the  electrical  energies  of  the  acting  substances. 

70.  Mechanical  agitation,  also  favours  the  chemical  action  of  And  by  Me- 

bodies.  chanical 

Into  a wine  glass  full  of  water,  tinged  blue  with  the  infusion  of  cabbage  let  JL 
fall  a small  lump  of  solid  tartaric  acid.  The  acid,  if  left  at  rest,  even  during 
some  hours,  will  only  change  to  red  that  portion  of  the  infusion,  which  is  in 
immediate  contact  with  it.  Stir  the  liquid,  and  the  whole  will  immediately 
become  red. 

Sulphuric  acid  poured  into  alcohol  will  subside  to  the  bottom,  and  chemical  g 
action  will  take  place  only  at  the  touching  surfaces  of  the  two  substances — but 
it  will  be  brought  on  through  the  whole  mixture  by  agitation. 

71.  Some  bodies  evince  no  affinity  for  each  other.  Some 

* i i • 

Oil  and  water,  or  powdered  chalk  and  water,  may  be  agitated  together,  but  v°n(!g 
they  will  not  combine.  On  allowing  the  vessels  containing  them  to  remain  ata^ 
rest,  the  oil  or  water  rises  to  the  surface,  and  the  chalk  falls  to  the  bottom.  Exp.  ^ 

72.  The  intervention  of  a third  body  will  sometimes  promote  the  Union  pro- 
union of  two  other  bodies  which  have  no  affinity  for  each  other.  thir^body1 

Thus  oil  and  water  unite  immediately  on  adding  an  alkali,  as  caustic  potassa.  Exp. 

73.  It  very  frequently  happens,  on  the  contrary,  that  the  tenden- Or  destroy- 
cy  of  two  bodies  to  unite,  or  remain  in  combination  together.,  is ed- 
weakened  or  destroyed  by  the  addition  of  a third.  Thus  alcohol 

unites  with  water  in  such  a manner  as  to  separate  most  salts  from  it. 

A striking  instance  of  this  is  seen  in  a saturated  or  strong  solution  of  nitre  in  Exp. 
water.  If  to  this  there  be  added  an  equal  measure  of  alcohol,  the  greater  part 
of  the  nitre  instantly  falls  down. 

Or,  if  to  a solution  of  camphor  in  alcohol,  water  be  added,  the  water  will  Exp. 
unite  with  the  alcohol  and  the  camphor  will  be  separated. 

Oil  has  an  affinity  for  the  volatile  alkali,  ammonia,  and  will  unite  with  it,  gXpo 
forming  a soapy  substance  called  a liniment.  But  the  ammonia  has  a still  great- 
er attraction  for  sulphuric  acid  ; and  hence  if  the  acid  be  added  to  the  -liniment* 
the  alkali  will  quit  the  oil,  and  unite  by  preference  with  the  acid.. 

74.  The  affinity  existing  between  any  two  bodies,  is  inferred  from  ^o®nj^er 
their  entering  into  chemical  combination,  and  that  this  has  happened,  r°d>  n 
we  have  a proof  in  the  change  of  properties. 

75.  From  a great  number  of  facts,  it  appears  that  some'  bodies 
have  a stronger  tendency  to  unite  than  others,  and  that  the  union 
of  a substance  with  another  will  often  exclude,  or  even  bring  about 
the  separation  of  a third  substance  which  may  have  been  previously 
united  with  one  of  them.  This  preference  of  uniting,,  exhibited 

with  regard  to  other  bodies,  has  been  called  Elective  Affinity.  Thus’jj^)j*e 

To  a solution  of  camphor  in  alcohol  add  water ; the  camphor  will  be  separa-  g5p  j 
ted,  and  the  water  and  alcohol  will  unite. 

Add  to  water  a few  drops  of  sulphuric  acid  ; the  addition  of  a solution  of  Exp.  2. 
baryta  will  cause  the  separation  of  the  acid.  The  white  substance  that  wil1 
subside  will  be  a new  compound  of  sulphuric  acid  and  baryta. 

In  these  and  many  similar  cases  combination  and  decomposition 
occur. 

76.  When  a compound  is  decomposed  and  but  one  substance  is  Single, 
separated,  or  brought  into  combination,  the  affinity  has  been  called 
Single  Elective.  But  the  phenomena  are  often  more  complex. 

77.  When  two  compounds,  each  consisting  of  two  ingredients,  Double, 
are  decomposed  and  two  new  compounds  formed,  we  have  an  in- 
stance of  Double  Elective  Affinity. 

3 


18 


Attraction — Chemical. 


Chap.  1. 
Exp. 

Dt  compo- 
sition. 

Exp. 


Tables  of 
affinity, 


Objections 

to. 


Diagrams. 


Mix  together  a solution  of  carbonate  of  ammonia  and  hydrochlorate  of  lime  ; 
carbonate  of  lime  and  hydrochlorate  of  ammonia  will  be  formed, 

78.  The  knowledge  of  the  affinities  which  bodies  have  for  each 
other,  enables  us  to  separate  them  when  united,  or  to  perform  the 
process  of  decomposition.  Thus, 

In  a solution  of  nitrate  of  silver  (common  lunar  caustic)  place  a piece  of 
polished  copper;  it  will  soon  be  covered  with  metallic  silver.  The  solution 
will  have  been  decomposed,  and  the  silver  precipitated. 

79.  The  order  in  which  decompositions  take  place  has  been  ex- 
pressed in  tables,  of  which  the  following,  drawn  up  by  Geoffroy,  is 
an  example  : — 

SULPHUR IC  ACID. 

Baryta, 

Strontia, 

Potassa, 

Soda, 

Lime, 

Ammonia, 

Magnesia. 

This  table  signifies,  first,  that  sulphuric  acid  has  an  affinity  for  the 
substances  placed  below  the  horizontal  line,  and  may  unite  separately 
with  each  ; and,  secondly,  that  the  base  of  the  salts  so  formed  will  be 
separated  from  the  acid  by  adding  any  of  the  alkalies  or  earths  which 
stand  above  it  in  the  column.  Thusammouia  will  separate  magnesia, 
lime  ammonia,  and  potassa  lime  ; but  none  can  withdraw  baryta 
from  sulphuric  acid,  nor  can  ammonia  or  magnesia  decompose  sul- 
phate of  lime,  though  strontia  or  baryta  will  do  so.  Bergmann  con- 
ceived that  these  decompositions  are  solely  determined  by  chemical 
attraction,  and  that  consequently  the  order  of  decomposition  repre- 
sents the  comparative  forces  of  affinity;  and  this  view,  from  the 
simple  and  natural  explanation  it  affords  of  the  phenomenon,  was  for 
a time  very  generally  adopted.  But  it  does  not  necessarily  follow, 
because  lime  separates  ammonia  from  sulphuric  acid,  that  the  lime 
has  a greater  attraction  for  the  acid  than  the  volatile  alkali.  Other 
causes  are  in  operation  which  modify  the  action  of  affinity  to  such  a 
degree,  that  it  is  impossible  to  discover  how  much  of  the  effect  is 
owing  to  that  power. 

80.  Berthollet  was  the  first  to  show  that  the  relative  forces  of 
chemical  attraction  cannot  always  be  determined  by  observing  the 
order  in  which  substances  separate  each  other  when  in  combination, 
and  that  the  tables  of  Geoffrov  are  merely  tables  of  decomposition, 
not  of  affinity.  He  likewise  traced  all  the  various  circumstances  that 
modify  the  action  of  affinity,  and  gave  a consistent  explanation  of  the 
mode  in  which  they  operate.  He  denied  the  existence  of  elective 
affinity  as  an  invariable  force,  capable  of  effecting  the  perfect  separa- 
tion of  one  body  from  another;  he  maintained  that  all  the  instances 
of  complete  decomposition  attributed  to  elective  affinity  are  in  real- 
ity determined  by  one  or  more  of  the  collateral  circumstances  that 
influence  its  operation.  But  here  this  acute  philosopher  went  too 
far.  Bergmann  erred  in  supposing  the  result  of  chemical  action  to 
be  in  every  case  owing  to  elective  affinity  ; but  Berthollet  ran  into 
the  opposite  extreme  in  declaring  that  the  effects  formerly  ascribed  to 
that  power  are  never  produced  by  it. 

81.  The  chemical  changes  are  often  illustrated  by  diagrams, 


19 


Influence  of  Cohesion. 

which  may  either  be  constructed  so  as  merely  to  show  the  result  of.  Sect* 
the  change,  or  may  exhibit  the  composition  of  the  acting  bodies. 

The  addition  of  sulphate  of  soda  to  nitrate  of  baryta  (both  in  solution),  will  be  Exp. 
attended  with  the  formation  of  sulphate  of  baryta  and  nitrate  of  soda. 

The  following  diagram  exhibits  the  substances  before  mixture,  on 
parallel  lines  ; after  mixture,  by  diagonal  lines  : 

Nitric  Acid.  Baryta. 


Sulphuric  Acid.  . 


Soda. 


Or  a more  complete  view  of  the  change  is  given  in  the  following 
diagram,  where  the  bodies  before  mixture  are  placed  upon  the  out- 
side of  the  perpendicular  lines ; their  component  parts  are  shown 
within  them  ; and  the  new  results  on  the  outside  of  the  horizontal 
lines. ^ 


Nitrate  of  Baryta. 


Nitrate  of  Soda. 

Nitric  Acid. 

Soda. 

Baryta. 

Sulphuric  Acid. 

Sulphate  of  Soda. 


Sulphate  of  Baryta. 


82.  Chemical  affinity  is  influenced  by  various  extraneous  eircum-  Circum- 
stances and  forces.  Of  these  the  most  important  are,  cohesion,  elas-  ®tance.s  in' 
ticity,  quantity  of  matter,  and  gravity.  To  these  may  be  added  the  affinity, 
agency  of  the  imponderables. 

S3.  The  first  obvious  effect  of  cohesion  is  to  oppose  affinity,  byc°hesion, 
impeding  or  preventing  that  mutual  penetration  and  close  proximity 
of  the  particles  of  different  bodies,  which  is  essential  to  the  success- 
ful exercise  of  their  attraction.  For  this  reason,  bodies  seldom  act 
chemically  in  their  solid  state.  Liquidity,  on  the  contrary,  favours 
chemical  action  ; it  permits  the  closest  possible  approximation,  while 
the  cohesive  power  is  comparatively  so  trifling  as  to  oppose  no  ap- 
preciable barrier  to  affinity. 

84.  Cohesion  may  be  diminished  in  two  ways,  by  mechanical  How  di- 
division, or  by  the  application  of  heat.  The  former  is  useful  by  in-  minished> 
creasing  the  extent  of  surface.  Heat  acts  with  greater  effect,  and 
never  fails  in  promoting  combination,  whenever  the  cohesive  power 
is  a barrier  to  it.  Its  intensity  should  always  be  so  regulated  as  to 
produce  liquefaction.  The  fluidity  of  one  of  the  substances  fre- 
quently suffices  for  effecting  chemical  union,  as  is  proved  by  the 
facility  with  which  water  dissolves  many  salts  and  other  solid  bodies. 

The  reduction  of  both  substances  to  the  liquid  state  is  the  best  me- 


* Various  methods  have  been  made  use  of  to  express  chemical  changes,  and  the  re- 
sults of  chemical  actions,  by  means  of  diagrams,  for  which  the  student  may  consult 
Henry’s  andBrande’s  Chem.,  the  Medical  Chemistry  of  Paris,  and  Ure’s  Dictionary , 
Art.  Attraction. 


20 


Attraction — Chemical . 


ChaP- 1»  thod  for  ensuring  chemical  action.  The  slight  degree  of  cohesion 
possessed  by  liquids  does  not  appear  to  cause  any  impediment  to  com- 
bination. It  seems  fair  to  infer,  that  very  little,  if  any,  affinity  exists 
between  two  bodies  which  do  not  combine  when  they  are  intimately 
mixed  in  a liquid  state. 

Agency  in  85.  The  phenomena  of  crystallization  are  owing  to  the  ascendancy 
tiontal  */a  c°hes*on  over  affinity.  When  a large  quantity  of  salt  has  been 
dissolved  in  water  by  the  aid  of  heat,  part  of  the  saline  matter  gene- 
rally separates  as  the  solution  cools,  because  the  cohesive  power  of 
the  salt  then  becomes  comparatively  too  powerful  for  chemical  at- 
traction. Its  particles  begin  to  cohere  together  and  are  deposited  in 
crystals,  the  process  of  crystallization  continuing  till  it  is  arrested  by 
the  affinity  of  the  liquid.  A similar  change  happens  when  a solution 
made  in  the  cold  is  gradually  evaporated.  The  cohesion  of  the 
saline  particles  is  no  longer  counteracted  by  the  affinity  of  the  liquid, 
and  the  salt,  therefore,  assumes  the  solid  form. 

Affects  re-  86.  Cohesion  plays  a still  more  important  part.  It  sometimes  de- 
termines the  result  of  chemical  action,  probably  even  in  opposition  to 
affinity. 


Exp. 


Its  action 
in  particu- 
lar cases. 


Exp. 


Thus,  on  mixing  together  a solution  of  two  acids  and  one  alkali,  of  which  two 
salts  may  be  formed,  one  soluble,  and  the  other  insoluble,  the  alkali  will  unite 
with  that  acid  with  which  it  forms  the  insoluble  compound,  to  the  exclusion  of 
the  other.  This  is  one  of  the  modifying  circumstances  employed  by  Berthollet 
to  account  for  the  phenomena  of  single  Elective  attraction,  and  is  certainly  appli- 
cable to  many  of  tne  instances  to  be  found  in  the  tables  of  affinity. 

87.  To  comprehend  the  manner  in  which  cohesion  nets  in  some 
instances,  it  ia  necessary  to  consider  what  takes  place  when  in  the 
same  liquid  two  or  more  compounds  are  brought  together,  which  do 
not  give  rise  to  an  insoluble  substance. 

Thus  on  mixing  solutions  of  sulphate  of  potnssa  and  nitrate  of  soda,  no  precipi- 
tate ensues  ; because  the  salts,  capable  of  being  funned  by  double  decomposition, 
sulphate  of  soda  and  nitrate  of  potnssa,  are  likewise  soluble.  In  this  case  it  is 
possible  either  that  each  acid  may  be  confined  to  one  base,  so  as  to  constitute  two 
neutral  salts  : or  that  each  acid  may  be  divided  between  both  bases,  yielding 
four  neutral  salts.  It  is  difficult  to  decide  this  point  in  an  unequivocal  manner: 
but  judging  from  many  chemical  phenomena,  it  is  probable  that  the  arrangement 
last  mentioned  is  the  most  frequent,  and  is  probably  universal  whenever  the  rela- 
tive forces  of  affinity  are  not  very  unequal.  When  two  acids  and  two  bases  meet 
together  in  neutralizing  proportion,  it  may,  therefore,  be  inferred,  that  each  acid 
unites  with  both  the  bases  in  a munnor  regulated  by  their  respective  forces  of 
affinity,  and  that  four  salts  are  contained  in  solution.  In  like  manner  the  pre- 
sence of  three  acids  and  three  bases  will  give  rise  to  nine  salts  ; and  when  four 
of  each  are  presont,  sixteen  salts  will  be  produced.  This  view  affords  the  most 
plausible  theory  of  the  constitution  of  mineral  waters,  and  of  the  products  which 
they  yield  by  evaporation.  T. 


Influence  of  88.  The  influence  of  insolubility  in  determining  the  result  of  che- 
insolubil-  mical  action  may  be  readily  explained  on  this  principle.  If  nitric 
acid,  sulphuric  acid,  and  baryta,  are  mixed  together  in  solution,  the 
base  may  be  conceived  to  be  at  first  divided  between  the  two  acids, 
and  nitrate  and  sulphate  of  baryta  to  be  generated.  The  latter  being 
insoluble  is  instantly  removed  beyond  the  influence  of  the  nitric  acid, 
so  that  for  an  instant  nitrate  of  baryta  and  free  sulphuric  acid  remain 
in  the  liquid  ; but  as  the  base  left  in  solution  is  again  divided  between 
the  two  acids,  a fresh  quantity  of  the  insoluble  sulphate  is  generated ; 
and  this  process  of  partition  continues,  until  either  the  baryta  or  the 


Influence  of  Heat.  21 

sulphuric  acid  is  withdrawn  from  the  solution.  Similar  changes  en-  Seet.  11. 
sue  when  nitrate  of  baryta  and  sulphate  of  soda  are  mixed. ^ 

89.  The  efflorescence  of  a salt  is  sometimes  attended  with  a simi-  of  efflores- 
lar  result.  If  carbonate  of  soda  and  chloride  of  calcium  are  mingled  cence, 
together  in  solution,  the  insoluble  carbonate  of  lime  subsides.  But  if 
carbonate  of  lime  and  sea-salt  are  mixed  in  the  solid  state,  and  a 
certain  degree  of  moisture  is  present,  carbonate  of  soda  and  chloride 

of  calcium  are  slowly  generated  , and  since  the  former,  as  soon  as 
it  is  formed,  separates  itself  from  the  mixture  by  efflorescence,  its 
production  continues  progressively.  The  efflorescence  of  carbonate 
of  soda,  which  is  sometimes  seen  on  old  walls,  or  which  in  some 
countries  is  found  on  the  soil,  appears  to  have  originated  in  this 
manner. 

90.  From  the  obstacle  which  cohesion  puts  in  the  way  of  affinity,  of  elastic- 
the  gaseous  state,  in  which  the  cohesive  power  is  wholly  wanting,  ity, 
might  be  expected  to  be  peculiarly  favourable  to  chemical  action. 

The  reverse,  however,  is  the  fact.  Bodies  evince  little  disposition  to 
unite  when  presented  to  each  other  in  the  elastic  form.  Combina- 
tion does  indeed  sometimes  take  place  in  consequence  of  a very 
energetic  attraction  ; but  examples  of  an  opposite  kind  are  much 
more  common.  This  want  of  action  seems  to  arise  from  the  distance 
between  the  particles  preventing  that  close  approximation  which  is 
so  necessary  to  the  successful  exercise  of  affinity.  Hence  many 
gases  cannot  be  made  to  unite  directly,  which  nevertheless  combine 
readily  while  in  their  nascent  state;  that  is- while  in  the  act  of  as- 
suming the  gaseous  form  by  the  decomposition  of  some  of  their  solid 
or  fluid  combinations. 

Elasticity  operates  likewise  as  a decomposing  agent.  If  two  gases, 
the  reciprocal  attraction  of  which  is  feeble,  suffer  considerable  con- 
densation when  they  unite,  the,  compound  will  be  decomposed  by 
very  slight  causes.  Chloride  of  nitrogen  affords  an  apt  illustration 
of  this  principle,  being  distinguished  for  its  remarkable  facility  of 
decomposition. 

91.  Many  familiar  phenomena  of  decomposition  are  owing  to  Of  heat, 
elasticity.  All  compounds  that  contain  a volatile  and  a fixed  prin- 
ciple, are  liable  to  be  decomposed  by  a high  temperature.  The  ex- 
pansion occasioned  by  heat  removes  the  elements  of  the  compound 

to  a greater  distance  from  each  other,  and  thus  by  diminishing  the 
force  of  chemical  attraction,  favours  the  tendency  of  the  volatile  prin- 
ciple to  assume  the  form  which  is  natural  to  it.  The  evaporation  of 
water  from  a solution  of  salt  is  an  instance  of  this  kind. 


* The  separation  of  salts  by  crystallization,  from  mineral  waters  or  other  saline  mix- 
tures, is  explicable  by  a similar  mode  of  reasoning.  Thus  on  mixing  nitrate  of  potassa 
and  sulphate  of  soda,  four  salts,  according  to  this  view,  are  generated,  namely,  the 
sulphates  of  soda  and  potassa,  and  the  nitrates  of  those  bases  ; and  if  the  solution  be 
allowed  to  evaporate  gradually,  a point  at  length  arrives  when  the  least  soluble  of 
these  salts,  the  sulphate  of  potassa,  will  be  disposed  to  crystallize.  As  soon  as 
some  of  its  crystals  are  deposited,  and  thus  withdrawn  from  the  influence  of  the  other 
salts,  the  constituents  of  these  undergo  a new  arrangement,  whereby  an  additional 
quantity  of  sulphate  of  potassa  is  generated  ; and  thijs  process  continues  until  the 
greater  part  of  the  sulphuric  acid  and  potassa  has  combined,  and  the  compound  is  re- 
moved by  crystallization.  If  the  difference  in  solubility  is  considerable,  the  separa- 
tion of  salts  may  be  often  rendered  very  complete  by  this  method.  T. 


22 


Attraction — Chemical. 


ChaP*  I-  Many  solid  substances,  which  contain  water  in  a state  of  intimate 
combination,  part  with  it  in  a strong  heat  in  consequence  of  the 
volatile  nature  of  that  liquid.  The  separation  of  oxygen  from  some 
metals,  by  heat  alone,  is  explicable  on  the  same  principle. 

Heat  may  92.  It  appears  that  the  influence  of  heat  over  affinity  is  variable  ; 
favour  or  for  at  one  time  it  promotes  chemical  union,  and  opposes  it  at  another. 

Its  action,  however,  is  always  consistent.  Whenever  the  cohesive 
power  is  an  obstacle  to  combination,  heat  favours  affinity  either  by 
diminishing  the  cohesion  of  a solid,  or  by  converting  it  into  a liquid. 
As  the  cause  of  the  gaseous  state,  on  the  contrary,  it  keeps  at  a dis- 
tance particles  which  would  otherwise  unite ; or,  by  producing 
expansion,  it  tends  to  separate  from  one  another  substances  which 
are  already  combined. 

Influence  of  93.  Some  of  the  decompositions,  which  were  attributed  by  Berg* 
ondecom-  mann  t0  l^e  so^e  influence  of  elective  affinity,  may  be  ascribed  to 
positions,  elasticity.  If  three  substances  are  mixed  together,  two  of  which  can 
form  a compound  which  is  less  volatile  than  the  third  body,  the  last 
will,  in  general,  be  completely  driven  off  by  the  application  of  heat. 
The  decomposition  of  the  salts  of  ammonia  by  the  pure  alkalies  or 
alkaline  earths,  may  be  adduced  as  an  example. 

On  results  94.  The  influence  of  elasticity  in  determining  the  result  of  che- 
of  chemical  mical  action  in  these  instances,  seems  owing  to  the  same  cause 
action,  which  enables  insolubility  to  be  productive  of  similar  effects.  Thus, 
on  mixing  hydrochlorate  of  ammonia  with  lime,  the  acid  is  divided 
between  the  two  bases;  some  ammonia  becomes  free,  which,  in 
consequence  of  its  elasticity,  is  entirely  expelled  by  a gentle  heat. 
The  acid  of  the  remaining  hydrochlorate  of  ammonia  is  again  divided 
between  the  two  bases ; and  if  a sufficient  quantity  of  lime  is  pre- 
sent, the  ammoniacal  salt  will  be  completely  decomposed. 

95.  The  influence  of  quantity  of  matter  over  affinity,  is  utiiver- 
Of  quantity  sally  admitted.  If  one  body  a unites  with  another  body  b in  several 
of  matter,  proportions,  that  compound  will  be  most  difficult  of  decomposition 

which  contains  the  smallest  quantity  of  b.  Of  the  three  oxides  of 
lead,  for  instance,  the  peroxide  parts  most  easily  with  its  oxygen 
by  the  action  of  heat;  a higher  temperature  is  required  to  decom- 
pose the  red  oxide ; and  the  protoxide  will  bear  the  strongest  heat 
of  our  furnaces  without  losing  a^parlicle  of  its  oxygen. 

96.  The  influence  of  quantity  over  chemical  attraction,  may  be 
hxample.  furt|ler  illustrated  by  the  phenomena  of  solution.  When  equal 

weights  of  a soluble  salt  are  added  in  succession  to  a given  quantity 
of  water,  which  is  capable  of  dissolving  almost  the  whole  of  the  salt 
employed,  the  first  portion  of  the  salt  will  disappear  more  readily 
than  the  second,  the  second  than  the  third,  the  third  than  the  fourth, 
and  so  on.  The  affinity  of  the  water  for  the  saline  substance,  dimi- 
nishes with  each  addition,  till  at  last  it  is  weakened  to  such  a degree 
as  to  be  unable  to  overcome  the  cohesion  of  the  salt.  The  process 
then  ceases,  and  a saturated  solution  is  obtained.* 


* Quantity  of  matter  is  employed  advantageously  in  many  chemical  operations.  If, 
for  instance,  a chemist  is  desirous  of  separating  an  acid  from  a metallic  oxide  by 
means  of  the  superior  affinity  of  potassa  for  the  former,  he  frequently  uses  rather 
more  of  the  alkali  than  is  sufficient  for  neutralizing  the  acid.  He  takes  the  precau- 
tion of  employing  an  excess  of  alkali,  in  order  the  more  effectually  to  firing  every 
particle  of  the  substance  to  be  decomposed  in  contact  with  the  decomposing  agent. 


Measure  of  Affinity. 


23 


97.  But  Berthollet  attributed  a much  greater  influence  to  quanti-  Sefct.  II. 
ty  of  matter.  It  was  the  basis  of  his  doctrine,  developed  in  the  Berthollet’? 
Statique  Chimique , that  bodies  cannot  be  wholly  separated  from  views' 
each  other  by  the  affinity  of  a third  substance  for  one  element  of  a 
compound  ; and  to  explain  why  a superior  chemical  attraction  does 

not  produce  the  effect  which  might  be  expected  from  it,  he  contend- 
ed that  quantity  of  matter  compensates  for  a weaker  affinity. 

Berthollet  confounded  two  things,  namely,  force  of  attraction  and 
neutralizing  power,  which  are  really  different,  and  ought -to  be  held 
distinct.  M.  Dulong  has  also  found  that  the  principle  of  Berthollet 
is  not  in  accord  with  the  results  of  experiment,  t.  i33. 

98.  The  influence  of  gravity  is  perceptible  when  it  is  wished  to  influence 
make  two  substances  unite,  the  densities  of  which  are  different.  In  °f  gravity, 
a case  of  simple  solution,  a larger  quantity  of  saline  matter  is  found 

at  the  bottom  than  at  the  top  of  the  liquid,  unless  the  solution  shall 
have  been  well  mixed  subsequently  to  its  formation.  In  making  an 
alloy  of  two  metals,  which  differ  from  one  another  in  density,  a 
larger  quantity  of  the  heavier  metal  will  be  found  at  the  lower  than 
in  the  upper  part  of  the  compound  ; unless  great  care  be  taken  to 
counteract  the  tendency  of  gravity  by  agitation.  This  force  obvious- 
ly acts,  like  the  cohesive  power,  in  preventing  a sufficient  degree  of 
approximation. 

99.  Pressure  has  an  important  influence  upon  chemical  action.  It  of  pres- 
appears  to  operate  both  by  bringing  the  particles  into  closer  contact,  sure, 
and  by  inducing  elevation  of  temperature.  As  when  chlorate  of  po- 

tassa  and  phosphorus  are  ignited  by  percussion. 

100.  The  chemical  agency  of  galvanism,  and  the  effects  of  light  and  of  impon- 
electricity,  will  be  most  conveniently  stated  in  other  parts  of  the  derabies, 
work.  t.  123. 

101.  As  the  order  of  decomposition  is  not  always  a satisfactory  Measure  of 
measure  of  the  force  of  affinity,  when  no  disturbing  causes  operate,  affinity, 
the  phenomena  of  decomposition  afford  a sure  criterion  ; but  when 

the  conclusions  obtained  in  this  way  are  doubtful,  assistance  may 
be  derived  from  other  sources.  The  surest  indications  are  procured 
by  observing  the  tendency  of  different  substances  to  unite  with  the 
same  principle,  under  the  same  circumstances,  and  subsequently  by 
marking  the  comparative  facility  of  decomposition  by  the  same  de- 
composing agent.  Thus,  on  exposing  silver,  lead,  and  iron,  to  air 
and  moisture,  the  iron  soon  rusts,  the  lead  is  oxidized  in  a slight  de- 
gree only,  and  the  silver  resists  oxidation  altogether.  It  is  hence 
inferred  that  iron  has  the  greatest  affinity  for  oxygen,  lead  next,  and 
silver  the  least.  It  is  inferred  from  the  action  of  heat  on  the  carbo- 
nate of  potassa,  baryta,  lime,  and  oxide  of  lead,  that  potassa  has  a 
stronger  attraction  for  carbonic  acid  than  baryta,  baryta  than  lime, 
and  lime  than  oxide  of  lead. 

102.  Of  all  chemical  substances,  our  knowledge  of  the  relative  de-  Of  acids 
grees  of  attraction  of  acids  and  alkalies  for  each  other  is  the  most  ^ alka" 
uncertain.  Their  action  on  one  another  is  affected  by  so  many,  cir- 
cumstances, that  it  is  in  most  cases  impossible,  with  certainty,  to  re- 
fer any  effect  to  its  real  cause,  t. 

103.  Substances  which  unite  chemically  have  been  found  to  do  so  Substances 
in  certain  proportions.  In  some  cases  they  are  united  in  a great  unite.in 
many  proportions, in  others  only  in  a few.  In  a few  instances  combi-  portions, 


24 


A ttr  action — Chemical. 


Chap.  I. 
Unlimited, 


Limited, 


Character 
of  com- 
pounds of 
many  pro- 
portions, 

Of  few. 


Laws. 
First  law. 


How  ac- 
counted for. 


nation  takes  place  unlimitedly  in  all  proportions  ; in  others  it  occurs 
, in  every  proportion  within  a certain  limit.  The  union  of  water  with 
alcohol  and  the  liquid  acids,  such  as  the  sulphuric,  hydrochloric,  and 
nitric  acids,  affords  instances  of  the  first  mode  of  combination  ; the 
solutions  of  salts  in  water  are  examples  of  the  second.  One  drop 
of  sulphuric  acid  may  be  diffused  through  a gallon  of  water,  or  a drop 
of  water  through  a gallon  of  the  acid  ; or  they  may  be  mixed  to- 
gether in  any  intermediate  proportions  ; and  in  each  case  they  ap- 
pear to  unite  perfectly  with  each  other.  A hundred  grains  of  water, 
on  the  contrary,  will  dissolve  any  quantity  of  sea-salt  which  does 
not  exceed  forty  grains.  Its  solvent  power  then  ceases,  because  the 
cohesion  of  the  solid  becomes  comparatively  too  powerful  for  the 
f<?rce  of  affinity.  The  limit  to  combination  is  in  such  instances  ow- 
ing to  the  cohesive  power ; and  but  for  the  obstacle  which  it  occa- 
sions, the  salt  would  most  probably  unite  with  water  in  every  pro- 
portion. 

104.  All  the  substances  that  unite  in  many  proportions,  give  rise  to 
compounds  which  have  this  common  character,  that  their  elements 
are  united  by  a feeble  affinity,  and  preserve,  when  combined,  more 
or  less  of  the  properties  which  they  possess  in  a separate  state. 

105.  The  most  interesting  series  of  compounds  is  produced  by  sub- 
stances which  unite  in  a few  proportions  only  ; and  which,  in  com- 
bining, lose  more  or  less  completely  the  properties  that  distinguish 
them  when  separate.  Of  these  bodies,  some  form  but,  one  combi- 
nation. Others  combine  in  two  proportions.  Others  again  unite  in 
three,  four,  five,  or  even  six  proportions,  which  is  the  greatest  num- 
ber of  compounds  that  any  two  substances  are  known  to  produce, 
except  perhaps  carbon  and  hydrogen,  and  those  which  belong  to  the 
first  division. 

106.  The  combination  of  substances  that  unite  in  a few  propor- 
tions only,  is  regulated  by  the  three  following  remarkable  laws: — 

1.  The  first  law  is,  that  the  composition  of  bodies  is  fixed  and 
invariable.  A compound  substance,  so  long  as  it  retains  its  charac- 
teristic properties,  always  consists  of  the  same  elements  united  to- 
gether in  the  same  proportion.  Water  is  formed  of  1 part*  of  hy- 
drogen and  8 of  oxygen  ; and*  were  these  two  elements  to  unite  in 
any  other  proportion,  some  new  compound,  different  from  water, 
would  be  the  product.  The  same  observation  applies  to  all  other 
substances,  however  complicated,  and  at  whatever  period  they  were 
produced.  This  law  is  universal  and  permanent.  Its  importance  is 
equally  manifest : it  is  the  essential  basis  of  chemistry. 

107.  Two  views  have  been  proposed  by  way  of  accounting  for  this 
law.  The  explanation  now  universally  given,  is  confined  to  a mere 
statement,  that  substances  are  disposed  to  combine  in  those  propor- 
tions to  which  they  are  so  strictly  limited,  in  preference  to  any  oth- 
ers ; it  is  regarded  as  an  ultimate  fact,  because  the  phenomena  are 
explicable  on  no  other  known  principle. 

The  tendency  of  bodies  to  unite  in  definite  proportions  only,  is  so 
great  as  to  excite  a suspicion  that  all  substances  combine  in  this 
way ; and  that  the  exceptions  thought  to  be  afforded  by  the  pheno- 
mena of  solution,  are  rather  apparent  than  real. 


* By  the  expression  “ parts”  is  meant  parts  by  weight. 


Neutral  Compounds.  25 

108.  The  second  law  of  combination  is,  that  the  relative  quanti-  Sect,  n. 
ties  in  which  bodies  unite  may  be  expressed  by  proportional  num-  Second 
bers.  Thus,  8 parts  of  oxygen  unite  with  1 part  of  hydrogen,  16.1 law- 

of  sulphur,  35.42  of  chlorine,  39.6  of  selenium,  and  108  parts  of 
silver.  Such  are  the  quantities  of  these  five  bodies  which  are  dis- 
posed to  unite  with  8 parts  of  oxygen  ; and  it  is  found  that  when 
they  combine  with  one  another,  they  unite  either  in  the  proportions 
expressed  by  those  numbers,  or  in  multiples  of  them  according  to 
the  third  law  of  combination. 

109.  From  the  occurrence  of  such  proportional  numbers  has  aris-  Equiva- 
en  the  use  of  certain  terms,  as  Proportion , Combining  Proportion , lents>  &c- 
Proportional , and  Chemical  Equivalent , or  Equivalent , to  express 

them.  The  fatter  term,  introduced  by  Wollaston,  was  suggested  by 
the  circumstance  that  the  combining  proportion  of  one  body  is, 
as  it  were,  equivalent  to  that  of  another  body,  and  may  be  substitu- 
ted for  it  in  combination.  . 

110.  This  law  does  not  apply  to  elementary  substances  only,  since  lennTof 
compound  bodies  have  their  combining  proportions  or  equivalents,  compounds, 
which  may  likewise  be  expressed  in  numbers.  Thus,  since  water  is 
composed  of  one  equivalent  or  8 parts  of  oxygen,  and  one  equiva- 
lent or  1 of  hydrogen,  its  combining  proportion  or  equivalent  is  9. 

The  equivalent  of  sulphuric  acid  is  40.1,  because  it  is  a compound 
of  one  equivalent  or  16.1  parts  of  sulphur,  and  three  equivalents  or 
24  parts  of  oxygen.  The  equivalent  number  of  potassium  is  39.15, 
and  as  that  quantity  combines  with  8 of  oxygen  to  form  potassa, 
the  equivalent  of  the  latter  is  39. 15— |— 8=47. 15.  Now  when  these 
compounds  unite,  one  equivalent  of  the  one  combines  with  one,  two, 
three,  or  more  equivalents  of  the  other,  precisely  as  the  simple  sub- 
stances do.  The  equivalent  of  sulphate  of  potassa  will  therefore  be 
40.1+47.15=87.25. 

111.  The  composition  of  the  salts  affords  a very  instructive  illus-  Examples, 
tration  of  this  subject;  and  to  exemplify  it  still  further,  a list  of  the 
equivalents  of  a few  acids  and  alkaline  bases  is  annexed: — 


Hydrofluoric  acid 

19.68 

Lithia 

14.44 

Phosphoric  acid 

71.4 

Magnesia 

20.7 

Hydrochloric  acid 

36,42 

Lime 

28.5 

Sulphuric  acid 

40.1 

Soda 

31.3 

Nitric  acid 

54.15 

Potassa 

47.15 

Arsenic  acid 

115.4 

Strontia 

51.8 - 

Selenic  acid 

63.6 

Baryta 

76.7 

It  will  be  seen  at  a glance  that  the  neutralizing  power  of  the  dif- 
ferent alkalies  is  very  different ; for  the  equivalent  of  each  base  ex- 
presses the  quantity  required  to  neutralize  an  equivalent  of  each  of 
the  acids.  Thus  14.44  of  lithia,  31.3  of  soda,  and  76.7  of  baryta, 
combine  with  54.15  of  nitric  acid,  forming  the  neutral  nitrates  of 
lithia,  soda,  and  baryta.  The  same  fact  is  obvious  with  respect  to 
the  acids  ; for  71.4  of  phosphoric,  40.1  of  sulphuric,  and  115.4  of 
arsenic  acid  unite  with  76.7  of  baryta,  forming  a neutral  phosphate, 
sulphate,  and  arseniate  of  baryta. 

112.  These  circumstances  afford  a ready  explanation  of  a curious  Neutrai 
fact,  first  noticed  by  the  Saxon  chemist  Wenzel ; namely,  that  when  compounds, 
two  neutral  salts  mutually  decompose  each  other,  the  resulting  com- 
pounds are  likewise  neutral.  The  cause  of  this  fact  is  now  obvious. 

If  71.4  parts  of  neutral  sulphate  of  soda  are  mixed  with  130.85  of 

4 


26 


Attraction — Chemical. 


Chap.  L 


Third  law. 

Ratios. 

Whole 

numbers. 


Half  equiv 
alents. 


nitrate  of  baryta,  the  76.7  parts  of  baryta  unite  with  40.1  of  sulphuric 
acid,  and  the  54.15  parts  of  nitric  acid  of  the  nitrate  combine  with 
the  31.3  of  soda  of  the  sulphate,  not  a particle  of  acid  or  alkali  re- 
maining- in  an  uncombined  condition. 

Sulphate  of  Soda.  Nitrate  of  Baryta. 

Sulphuric  acid  . 40.1  54.15  Nitric  acid, 

Soda  . . . 31.3  76.7  Baryta, 


71.4  130.85 

It  matters  not  whether  more  or  less  than  71.4  parts  of  sulphate 
of  soda  are  added  ; for  if  more,  a small  quantity  of  sulphate  of  so- 
da will  remain  in  solution  ; if  less,  nitrate  of  baryta  will  be  in  ex- 

cess ; but  in  either  case  the  neutrality  will  be  unaffected. 

113.  The  third  law  of  combination  is,  that  when  one  body  a 
unites  with  another  body  b in  two  or  more  proportions,  the  quanti- 
ties of  the  latter,  united  with  the  same  quantity  of  the  former,  bear 
to  each  other  a very  simple  ratio.  The  progress  of  chemical  re- 
search, in  discovering  new  compounds  and  ascertaining  their  exact 
composition,  has  shown  that  these  ratios  of  b may  be  represented 
by  one  or  other  of  the  two  following  series  : — 

1st  Series,  a unites  with  1,  2,  3,  4,  5,  &c.  of  b. 

2d  Series,  a unites  with  1,  1£,  2,  24,  &c.  of  b. 


The  first  series  is  exemplified  by  the  subjoined  compounds  : 


Water  is  composed  of 

Hydrogen 

1 

Oxygen  8 , 

) 1 

Binoxide  of  hydrogen 

'Do. 

1 

Do.  16  < 

is 

Carbonic  oxide 

Carbon 

6.12 

Do.  8j 

1 1 

Carbonic  acid 

Do. 

6.12  . 

Do.  16  < 

12 

Nitrous  oxide 

Nitrogen 

14.15 

Do.  8i 

I 1 

Nitric  oxide 

Do. 

14.15 

Do.  16  | 

1 2 

Hyponitrous  acid  . 

Do. 

14.15 

Do.  21 

Y3 

Nitrous  acid 

Do. 

14.15 

Do.  32  | 

4 

Nitric  acid 

Do. 

14.15 

Do.  40  J 

1 5 

It  is  obvious  that  in  all  these  compounds  the  ratios  of  the  oxygen 
are  expressed  by  whole  numbers.  In  water  the  hydrogen  is  com- 
bined with  half  as  much  oxygen  as  in  the  binoxide  of  hydrogen,  so 
that  the  ratio  is  as  1 to  The  same  relation  holds  in  carbonic 
oxide  and  carbonic  acid.  The  oxygen  in  the  compounds  of  nitro- 
gen and  oxygen  is  in  the  ratio  of  1,  2,  3,  4,  and  5.  In  like  manner 
the  ratio  of  sulphur  in  the  two  sulphurets  of  mercury,  and  that  of 
chlorine  in  the  two  chlorides  of  mercury,  is  as  1 to  2.  So,  in  bicar- 
bonate of  potassa,  the  alkali  is  united  with  twice  as  much  carbonic 
acid  as  in  the  carbonate  ; and  the  acid  of  the  three  oxalates  of  po- 
tassa is  in  the  ratio  of  1,  2,  and  4. 

The  following  compounds  exemplify  the  second  series  : — 


Protoxide  of  iron  consists  of  Iron 

28 

Oxygen 

s; 

[ 1 

Sesquioxide  or  Peroxide  . 

. Do. 

28 

Do. 

12  < 

M4 

Protoxide  of  manganese  . 

Manganese 

27.7 

Do. 

8i 

>1 

Sesquioxide* 

. Do. 

27.7 

Do. 

12 ; 

Binoxide 

. Do. 

27.7 

Do. 

16* 

12 

Arsenious  acid 

. Arsenic 

37.7 

Do. 

12  1 

[14 

Arsenic  acid 

. Do. 

37.7 

Do. 

20  < 

>24 

Hypophosphorous  acid 

Phosphorus 

15.7 

Do. 

4 ] 

) 4 

Phosphorous  acid 

Do. 

15.7 

Do. 

12 

,14 

Phosphoric  acid 

Do. 

15.7 

Do. 

20  * 

124 

♦ The  Latin  sesqui , one  and  a half,  is  used  when  the  elements  of  an  oxide,  chloride, 
&c.,  are  as  1 to  l£  or  as  2 to  3. 


27 


Laws  of  Combination . 


Both  of  these  series,  which  together  constitute  the  third  law  of  Sect,  n. 
combination,  result  naturally  from  the  operation  of  the  second  law. 

The  first  series  arises  from  one  equivalent  of  a body  uniting  with 
1,  2,  3,  or  more  equivalents  of  another  body.  The  second  series  is 
a consequence  of  two  equivalents  of  one  substance  combining  with 
3,  5,  or  more  equivalents  of  another.  Thus  if  two  equivalents  of 
phosphorus  unite  both  with  3 and  with  5 equivalents  of  oxygen,  we 
obtain  the  ratio  of  1£  to  2h  ; and  should  one  equivalent  of  iron  com- 
bine with  one  of  oxygen,  and  another  compound  be  formed  of  two 
equivalents  of  iron  to  three  of  oxygen,  then  the  oxygen  united  with 
the.  same  weight  of  iron  would  have  the  ratio,  as  in  the  table,  of  1 
to  1£.  Still  more  complex  arrangements  will  be  readily  conceived,  More  com- 
such  as  3 equivalents  of  one  substance  to  4,  5,  or  more  of  another,  plex 
But  it  is  remarkable  that  combinations  of  the  kind  are  very  rare  ; 
and  even  their  existence,  though  theoretically  possible,  has  not  been 
decidedly  established.^ 

114.  The  utility  of  being  acquainted  with  these  important  laws  is  Advanta- 
almost  too  manifest  to  require  mention  Through  their  aid,  and  by^°  1 es@ 
remembering  the  equivalents  of  a few  elementary  substances,  the 
composition  of  an  extensive  range  of  compound  bodies  may  be  cal- 
culated with  facility.  Thus,  by  knowing  that  6.12  is  the  equivalent 
of  carbon  and  8 of  oxygen,  it  is  easy  to  recollect  the  composition  of 
carbonic  oxide  and  carbonic  acid  ; the  first  consisting  of  6.12  parts 
of  carbon  -j-  8 of  oxygen,  and  the  second  of  6.12  carbon  -j-  16  of 
oxygen.  The  equivalent  of  potassium  is  39.15;  and  potassa,  its 
protoxide,  is  composed  of  39.15  of  potassium  -j-  8 of  oxygen.  From 
these  few  data,  we  know  at  once  the  composition  of  carbonate  and 
bicarbonate  of  potassa;  the  former  being  composed  of  22.12  parts 
of  carbonic  acid  -j-  47.15  potassa,  and  the  latter  of  44.24  carbonic 
acid  + 47.15  potassa.  This  method  acts  as  an  artificial  memory, 
the  advantage  of  which,  compared  with  the  common  practice  of 
stating  the  composition  in  100  parts,  will  be  manifest  by  inspecting 
the  following  quantities,  and  attempting  to  recollect  them. 


Carbonic  Oxide. 
Carbon  42.86 

Oxygen  57.14 


Carbonic  Acid. 
27.27 
72.73 


Carbonate  of  Potassa. 
Carbonic  acid  31.43 
Potassa  68.57 


Bicarbonate  of  Potassa. 

47.83 

52.17 


From  the  same  data,  calculation's,  which  would  otherwise  be  diffi- 
cult or  tedious,  may  be  made  rapidly  and  with  ease,  without  refer- 


* The  merit  of  establishing  the  first  law  of  combination  seems  justly  due  to  Wen- 
zel a Saxon  chemist ; and  the  second  law  is  also  deducible  from  his  expenments  on 
the’ composition  of  the  salts.  His  work,  entitled  Lehre  der  Verwandtschaft,  was  pub- 
lislied  in  1777.  The  late  Mr  Higgins,  also,  in  1789,  speculated  on  the  atomic  consti- 
tution of  compound  bodies;  but  it  is  to  Dalton*  that  we  are  indebted  for  a theory  of 
chemical  union,  embracing  the  whole  science,  and  giving  it  a consistency  and  f 

before  his  time  it  had  never  possessed.  Of  all  who  have  sum »sfol y Jabou  ed 
in  establishing  the  laws  of  combination,  the  most  splendid  contribution  is  that  of  the 
celebrated  Berzelius, 


* New  System  of  Chem.  Philos.  1808. 


28 


Attraction — Chemical. 


Chap.  I. 
Uses, 


In  analysis. 


Numbers 
how  deter- 
mined. 


Essential 

point. 


ence  to  books,  and  frequently  by  a simple  mental  process.  The  ex- 
act quantities  of  substances  required  to  produce  a given  effect  may 
be  determined  with  certainly,  thus  affording  information  which  is 
often  necessary  to  the  success  of  chemical  processes,  and  of  great 
consequence  both  in  the  practice  of  the  chemical  arts,  and  in  the 
operations  of  pharmacy. 

115.  The  same  knowledge  affords  a good  test  to  the  analyst  by 
which  he  may  judge  of  the  accuracy  of  his  result,  and  even  some- 
times correct  an  analysis  which  he  has  not  the  means  of  performing 
with  rigid  precision.  Thus  a powerful  argument  for  the  accuracy 
of  an  analysis  is  derived  from  the  correspondence  of  its  result  with 
the  laws  of  chemical  union.  On  the  contrary,  if  it  form  an  excep- 
tion to  them,  we  are  authorized  to  regard  it  as  doubtful ; and  may 
hence  be  led  to  detect  an  error,  the  existence  of  which  might  not 
otherwise  have  been  suspected.  If  an  oxidized  body  be  found  to 
contain  one  equivalent  of  the  combustible  with  7.99  of  oxygen,  it  is 
fair  to  infer  that  8,  or  one  equivalent  of  oxygen,  would  have  been 
the  result,  had  the  analysis  been  perfect. 

The  composition  of  a substance  may  sometimes  be  determined  by 
a calculation,  founded  on  the  laws  of  chemical  union,  before  an 
analysis  of  it  has  been  accomplished. 

116.  The  method  of  determining  equivalent  numbers  will  be  an- 
ticipated from  what  has  already  been  said.  The  commencement  is 
made  by  carefully  analyzing  a definite  compound  of  two  simple  sub- 
stances which  possess  an  extensive  range  of  affinity.  Thus  water, 
a compound  of  oxygen  and  hydrogen,  is  found  to  contain  8 parts  of 
the  former  to  1 of  the  latter ; and  if  it  be  assumed  that  water  con- 
sists of  one  equivalent  of  oxygen  and  one  of  hydrogen,  the  relative 
weights  of  these  equivalents  will  be  as  8 to  1.  The  chemist  then 
selects  for  analysis  such  compounds  as  he  believes  to  contain  one 
equivalent  of  each  element,  in  which  either  oxygen  or  hydrogen, 
but  not  both,  is  present.  Carbonic  oxide  and  hydrosulphuric  acid 
are  suited  to  his  purpose : as  the  former  consists  of  8 parts  of 
oxygen  and  6.12  of  carbon,  and  the  latter  of  1 part  of  hydrogen  and 
16.1  of  sulphur,  the  equivalent  of  carbon  is  inferred  to  be  6.21,  and 
that  of  sulphur  16.1.  The  equivalents  of  all  the  other  elements 
may  be  determined  in  a similar  manner.* 

117.  Since  the  equivalents  merely  express  the  relative  quantities 
of  different  substances  which  combine  together,  it  is  in  itself  imma- 
terial what  figures  are  employed  to  express  them.  The  only  essen- 


* In  researches  on  chemical  equivalents  there  are  two  kinds  of  difficulty,  <?ne  in- 
volved in  the  processes  for  ascertaining  the  exact  composition  of  compounds,  and  the 
other  in  the  selection  of  the  compounds  which  contain  single  equivalents.  Impor- 
tant general  precautions  in  the  experimental  part  of  the  subject  are  the  following  : — 
1,  to  exert  scrupulous  care  about  the  purity  of  materials  ; 2,  to  select  methods  which 
consist  of  a few  simple  operations  only  ; 3,  to  repeat  experiments,  and  with  mate- 
rials prepared  at  different  times;  4,  to  arrive  at  the  same  conclusion  by  two  or  more 
processes  independent  of  each  other.  In  the  selection  of  compounds  of  single  equiv- 
alents, there  are  several  circumstances  calculated  to  direct  the  judgment ; for  wnich 
see  Turner’s  Elements  of  Chemistry,  p.  139.  The  ready  decomposition  by  galvan- 
ism, observed  by  Faraday,  of  compounds  which  consist  of  single  equivalents,  and 
the  resistance  to  the  same  agent  of  many  others  not  so  constituted,  promises  to  be- 
come an  indication  of  great  value  in  determining  equivalent  numbers. 


Atomic  Theory . 

tial  point  is,  that  the  relation  should  be  strictly  observed.  Thus,  Sect-  n. 
the  equivalent  of  hydrogen  may  be  assumed  as  10 ; but  then 
oxygen  must  be  80,  carbon  61.2  and  sulphur  16.1.  We  may  call  hy- 
drogen 100  or  1000 ; or,  if  it  were  desirable  to  perplex  the  subject  as 
much  as  possible,  some  high  uneven  number  might  be  selected,  pro- 
vided the  due  relation  between  the  different  numbers  were  faithful- 
ly preserved.  But  such  a practice  would  effectually  do  away  with 
the  advantage  above  ascribed  to  the  use  of  equivalents;  and  it  is 
the  object  of  every  one  to  employ  such  as  are  simple,  that  their  re- 
lation may  be  perceived  by  mere  inspection.  Thomson  makes 
oxygen  1,  so  that  hydrogen  is  eight  times  less  than  unity,  or  0.125, 
carbon  0.75,  and  sulphur  2.  Wollaston,  in  his  scale  of  chemical 
equivalents,  estimated  oxygen  at  10;  and  hence  hydrogen  is  1.25,  Unit, 
carbon  7.5  and  so  on.  According  to  Berzelius,  oxygen  is  100.  And 
lastly,  several  other  chemists,  such  as  Dalton,  Davy,  Henry,  and 
others,  selected  hydrogen  as  their  unit ; and,  therefore,  the  equiva- 
lent of  oxygen  is  8.  One  of  these  series  may  be  reduced  to  either 
of  the  others  by  an  obvious  and  simple  calculation.  The  numbers 
adopted  in  this  work  refer  to  hydrogen  as  unity.  T.  i4i. 

118.  These  equivalent  numbers,  when  once  well  ascertained  and  Woilas- 
arranged  in  a tabular  form,  become  a safe  and  invaluable  source  0fton’sscae' 
information  to  the  chemist.  By  adapting  a table  of  this  sort  to  a 
moveable  scale,  on  the  principle  of  Gunter’s  sliding  rule,  Wol- 
laston constructed  a logometric  scale  of  chemical  equivalents, 

which  is  capable  of  solving  with  great  facility  many  problems  of 
chemistry.* 

119.  To  account  for  the  laws  observed  with  regard  to  the  definite  Atomic 
combinations  of  bodies,  Dalton  proposed  what  may  be  termed,  the theory' 
atomic  theory  of  the  chemical  constitution  of  bodies.  The  laws 
themselves  are  the  deductions  from  experiment,  the  mere  expression 

of  the  facts,  and  are  not  necessarily  connected  with  any  speculation. 

120.  Two  opposite  opinions  have  long  existed  concerning  the  Atoms, 
ultimate  elements  of  matter.  It  is  supposed,  according  to  one  party,  wliat> 
that  every  particle  of  matter,  however  small,  m§y  be  divided  into 
smaller  portions,  provided  our  instruments  and  organs  were  adapted 

to  the  operation.  Their  opponents  contend,  on  the  other  hand,  that 
matter  is  composed  of  certain  ultimate  particles  or  molecules,  which 
by  their  nature  are  indivisible,  and  are  hence  termed  atoms  (from  a 
not  and  veyveiv  to  cut).  These  opposite  opinions  have  from  time  to 
time  been  keenly  contested,  and  the  progress  of  modern  che- 
mistry has  revived  attention  to  this  controversy.  We  have  only 
to  assume  with  Dalton,  that  all  bodies  are  composed  of  ulti- 
mate atoms,  the  weight  of  which  is  different  in  different  kinds  of 
matter,  and  we  explain  at  once  the  foregoing  laws  of  chemical 
union ; and  this  mode  of  reasoning  is,  in  the  present  case,  almost 
decisive,  because  the  phenomena  do  not  appear  explicable  on  any 
other  supposition. 

121.  According  to  the  atomic  theory,  every  compound  is  formed 


* For  description  of  this  instrument,  and  a table  of  chemical  equivalents  of  elemen- 
tary substances,  see  Appendix.  See  also  Faraday’s  Chemical  Manipulation. 


30 


Attraction — Chemical. 


ChaP-  L of  the  atoms  of  its  constituents.  An  atom  of  A may  unite  with  one, 
Form  com-  two,  three,  or  more  atoms  of  B.  Thus  supposing  water  to  be  com- 
pounds. posed  of  one  atom  of  hydrogen  and  one  atom  of  oxygen,  binoxide  of 
hydrogen  will  consist  of  one  atom  of  hydrogen  and  two  atoms  of 
oxygen.  If  carbonic  oxide  is  formed  of  one  atom  of  carbon  and  one 
atom  of  oxygen,  carbonic  acid  will  consist  of  one  atom  of  carbon  and 
two  atoms  of  oxygen. 

If,  in  the  compounds  of  nitrogen  and  oxygen  enumerated  at  (page 
26,)  the  first  or  protoxide  consist  of  one  atom  of  nitrogen  and  one 
atom  of  oxygen,  the  four  others  will  be  regarded  as  compounds  of 
one  atom  of  nitrogen  to  two,  three,  four,  and  five  atoms  of  oxygen. 
From  these  instances  it  will  appear,  that  the  law  of  multiple  propor- 
tions is  a necessary  consequence  of  the  atomic  theory.  There  is  also 
no  apparent  reason  why  two  or  more  atoms  of  one  substance  may 
not  combine  with  two,  three,  four,  five,  or  more  atoms  of  another ; 
but,  on  the  contrary,  these  arrangements  are  necessary  in  explana- 
tion of  the  not  unfrequent  occurrence  of  half  equivalents,  as  formerly 
stated.  (Page  27.)  Such  combinations  will  also  account  for  the 
complicated  proportion  noticed  in  certain  compounds,  especially  in 
many  of  those  belonging  to  the  animal  and  vegetable  kingdom. 

Use  of  the  122.  In  consequence  of  the  satisfactory  explanation  which  the  laws 
term  atom.  0f  chemical  union  receive  by  means  of  the  atomic  theory,  it  has 
become  customary  to  employ  the  term  atom  in  the  same  sense  as 
combining  proportion  or  equivalent.  For  example,  instead  of  de- 
scribing water  as  a compound  of  one  equivalent  of  oxygen  and  one 
equivalent  of  hydrogen,  it  is  said  to  consist  of  one  atom  of  each 
element.  In  like  manner  sulphate  of  potassa  is  said  to  be  formed  of 
one  atom  of  sulphuric  acid  and  one  atom  of  potassa  ; the  word  in  this 
case  denoting  as  it  were  a compound  atom,  that  is,  the  smallest  inte- 
gral particle  of  the  acid  or  alkali, — a particle  which  does  not  admit 
of  being  divided,  except  by  the  separation  of  its  elementary  or  con- 
stituent atoms.  The  numbers  expressing  the  proportions  in  which 
bodies  unite,  must  likewise  indicate,  consistently  with  this  view,  the 
relative  weights  #f  atoms  ; and  accordingly  these  numbers  are  often 
Atomic  called  atomic  weights.  Thus,  as  water  is  composed  of  8 parts  of  oxy- 
wdght.  g.en  an(j  j 0f  hydrogen,  it  follows,  on  the  supposition  of  water 
consisting  of  one  atom  of  each  element,  that  an  atom  of  oxygen  must 
be  eight  times  as  heavy  as  an  atom  of  hydrogen.  If  carbonic  oxide 
be  formed  of  an  atom  of  carbon  and  an  atom  of  oxygen,  the  relative 
weight  of  their  atoms  is  as  6.12  to  8;  and  in  short  the  chemical 
equivalents  of  all  bodies  may  be  considered  as  expressing  the  rela- 


tive weights  of  their  atoms. 

Arguments  123.  The  arguments  in  favour  of  the  atomic  constitution  of  matter 
in  support  become  much  stronger,  when  we  trace  the  intimate  connexion  which 
of  the  the-  subsists,  among  many  substances,  between  their  crystalline  form  and 
chemical  composition.  The  only  mode  of  satisfactorily  accounting 
for  the  striking  identity  of  crystalline  form  observable,  first,  between 
two  substances,  and  secondly,  between  all  their  compounds,  which 
have  an  exactly  similar  composition,  is  by  supposing  them  to  consist 
of  ultimate  particles,  possessed  of  the  same  figures,  and  arranged  in 
precisely  the  same  order.  The  phenomena  presented  by  isomor- 


31 


Union  of  Gases. 

phous  bodies  (50),  afford  a powerful  argument  in  favour  of  the  atomic  Sect.  n. 
theory.^  T.  418. 

124.  Soon  after  the  publication  of  Dalton’s  views  of  the  atomic  Tiieory  of 
constitution  of  bodies,!  a paper  appeared  by  Gay-Lussac,!  in  which  volumes, 
he  proved  that  gases  unite  together  by  volume  in  very  simple  and 
definite  proportions.  It  was  found  that  water  is  composed  precisely 

of  100  measures  of  oxygen  gas  and  200  measures  of  hydrogen  ; and 
Gay-Lussac,  being  struck  by  this  peculiary  simple  proportion,  was 
induced  to  examine  the  combinations  of  other  gases,  with  the  view 
of  ascertaining  if  any  thing  similar  occurred  in  other  instances. 

The  first  compounds  which  he  examined  were  those  of  ammoniacal 
gas  with  hydrochloric,  carbonic,  and  fluoboric  acid  gases.  100  vo- 
lumes of  the  alkali  were  found  to  combine  with  precisely  100  volumes 
of  hydrochloric  acid  gas,  and  they  could  be  made  to  unite  in  no  other 
ratio.  With  both  the  other  acids,  on  the  contrary,  two  distinct  com- 
binations were  possible.  These  are 

100  Fluoboric  acid  gas,  with  100  Ammoniacal  gas. 

100  do.  200  do. 

100  Carbonic  acid  gas  100  do. 

100  do.  200  do. 

Various  other  examples  were  quoted,  both  from  his  own  experi- 
ments and  from  those  of  others,  all  demonstrating  the  same  fact. 

125.  From  these  and  other  instances  Gay-Lussac  established  the  union  0f 
fact,  that  gaseous  substances  unite  in  the  simple  ratio  of  1 to  1,  1 to  gases. 

2,  1 to  3,  &c. ; and  this  original  observation  has  been  confirmed  by 

a multiplicity  of  experiments.  Nor  does  it  apply  to  gases  merely, 
but  to  vapours  also. 

126.  Another  remarkable  fact  established  by  Gay-Lussac  intheofcom- 
same  essay  is,  that  the  volumes  of  compound  gases  and  vapours  pound 
always  bear  a very  simple  ratio  to  the  volumes  of  their  elements.  Sases* 
Thus, 

Volumes  o f Elemen  ts . Volumes  o f resulting  Compounds . 

100  Nitrogen  gas  -j-  300  Hydrogen  gas  yield  200  Ammoniacal  gas. 

50  Oxygen  “ -j-  100  Hydrogen  “ . . . 100  Water. 

50  Oxygen  “ -j-  100  Nitrogen  “ . . . ] 00  Protoxide  of  nitrogen  gas. 

100  Chlorine  “ -f-  100  Hydrogen  “ . . . 200  Hydrochloric  acid  “ 

100  Iodine  “ -|-  100  Hydrogen  “ . . . 200  Hydriodic  acid  “ 

100  Oxygen  “ -j-  100  Nitrogen  “ . . . 200  Binoxide  of  nitrogen  “ 


* Dalton  supposes  that  the  atoms  of  bodies  are  spherical;  and  he  has  invented  cer- 
tain symbols  to  represent  the  mode  in  which  he  conceives  they  may  combine  together, 
as  illustrated  by  the  following  figures : 

0 Hydrogen.  - > O Oxygen. 

0 Nitrogen.  9 Carbon. 

BINARY  COMPOUNDS. 

O 0 Water. 

O 9 Carbonic  oxide. 

TERNARY  COMPOUNDS. 

O O O Binoxide  of  hydrogen. 

O • O Carbonic  acid. 

&c.  &c.  &c. 

All  substances  containing  only  two  atoms  he  called  binary  compounds  ; those  com- 
posed of  three  atoms,  ternary  compounds  ; of  four,  quaternary,  &c.  For  a more  full 
account  of  the  doctrine  of  atoms,  see  Daubeny  on  the  Atomic  Theory , and  Prout’s 
Bridgewater  Treatise. 

t New  System  of  Chem.  Philos.  1808.  t Mem.  d'Arcueil. 


32 


Jltttr  action — Chemical. 


volumes. 


Volumes  of  Elements. 
100  Nitrogen 


Chap.  I.  The  law  of  multiples  (page  26)  is  equally, demonstrable  by  means 
Combining  of  combining  volumes  as  by  combining  weights.  Thus, 

Resulting  Compounds- 
eld  Protoxide  of  nitrogen. 
Binoxide  of  nitrogen. 
Hyponitrous  acid. 
Nitrous  acid. 

Nitric  acid. 

Water. 

Binoxide  of  hydrogen. 
Carbonic  oxide. 
Carbonic  acid. 

nation  may  equally  well  be 


100 

100 

100 

100 


do. 

do. 

do. 

do. 


100  Hydrogen 
100  do. 

100  Carbon  vapour  -j- 
100  do 


t 

50  Oxygen 

+ 

100 

do. 

+ 

150 

do. 

+ 

200 

do. 

+ 

250 

do. 

+ 

50 

do. 

+ 

100 

do. 

+ 

50 

do. 

4- 

100 

do. 

Table  of 
equivalent 
weights, 
&c. 


It  thus  appears  that  the  laws  of  combi 
deduced  from  the  volumes  as  from  the  weights  of  the  combining 
substances,  and  that  the  composition  of  gaseous  bodies  may  be  ex- 
pressed as  well  by  measure  as  weight. 

127.  The  following  table  exhibitsa  view  of  equivalent  weights  and 
volumes,  to  which  are  added  the  respective  specific  gravities  in  rela- 
tion both  to  air  and  hydrogen. 


Gasrs  and  Vapovhs. 

Specific  Gravities. 

Chemical  Equivalents. 

Air  as  1. 

Hydrogen  as  1. 

By  Vol. 

By  Weight. 

Hydrogen,  ... 

M.ntW.i 

1.00 

100 

1. 

Nitrogen,  - 

0.9727 

14.15 

100 

14.15 

Chlorine,  ... 

2.4700 

35.42 

100 

35.42 

Carbon,  (hypothetical), 

0.4215 

6.12 

100 

6.12 

Iodine,  - 

8.7020 

126.30 

100 

126.3 

Bromine,  - 

6.4017 

78.40 

100 

78.4 

Water,  - 

Alcohol,  .... 

0.6201 

9.00 

100 

9. 

1.C009 

23.24 

100 

23.24 

Sulphuric  ether, 

Light  carburetted  hydrogen, 

2.5817 

37.48 

too 

37.48 

0.5593 

8.12 

100 

8.12 

Olefiant  gas,  ... 

Carbonic  oxide, 

0.9S08 

14.24 

100 

14.24 

0.9727 

14.12 

100 

14.12 

Carbonic  acid,  - 

l .6839 

22.12 

100 

22.12 

Protoxide  of  nitrogen, 

1.5239 

22.15 

100 

22.15 

Sulphurous  acid, 

2.2117 

32.10 

100 

32.1 

Sulphuric  acid,  (anhydrous) 

2.7629 

40.10 

100 

40.1 

Cyanogen,  - 
Hydrosulphuric  acid, 

1.8157 

26.39 

100 

26.39 

1.1782 

17.10 

100 

17.1 

Binoxide  of  nitrogen,  - 

1 .0375 

15.75 

200 

30.15 

Mercury,  - 

6.9689 

101.00 

200 

202. 

Ammonia,  - 

0.5897 

8.75 

200 

17.15 

Hydrochloric  acid,  - 

1.2694 

18.21 

200 

36.42 

Hydriodic  acid,  - 

4.3354 

63.65 

200 

127.3 

Hydrohromic  acid,  - 

2 7353 

39.70 

200 

79.4 

Hydrocyanic  acid, 

0.9423 

13.95 

200 

27.39 

Arseniuretted  hydrogen,  - 

2.7008 

39.20 

200 

78.4 

Sesquichloride  of  arsenic,  * 

6 3025 

90.83 

200 

181.66 

Sesquiodide  of  arsenic,  - 

15.6505 

227.15 

200 

454.3 

Protochloride  of  mercury,  - 

8.1939 

118.71 

200 

237.42 

Bichloride  of  mercury,  - 

9.4289 

136.42 

200 

272.84 

Bromide  of  mercury',  - 

9.6597 

140.20 

200 

280.4 

Bibromide  of  mercury,  - 

12.3606 

179  40 

200 

353.8 

Biniodide  of  mercury, 

15.6609 

227.30 

200 

454.6 

Oxvgen, 

1.1024 

16.00 

50 

8. 

Arsenious  acid,  «- 

13.6972 

198.80 

50 

99.4 

Phosphorus,  ... 

4.3269 

62.80 

25 

15.7 

Arsenic,  - 

10.3901 

150.80 

25 

37.7 

Sulphur,  .... 

6.6558 

96.60 

16.66 

16.1 

l.isulphuret  of  mercury,  - 

5.3788 

78.06 

300 

234.2 

Chemical  Symbols.  w 

128.  From  the  examination  of  the  table  it  will  be  seen,  1st,  that  Sect- IL 
the  combining  volumes  are  either  equal,  or  in  the  simple  ratio  of  1 to  Ratios  of 
2,  1 to  3,  &c.  The  same  simplicity  rarely  exists  among  the  equiva- 

lent  weights.  2.  The  specific  gravities  and  weights  of  the  18  first 
substances  are  seen  to  be  identical.  As  these  have  the  same  uniting  identity  of 
volume  as  hydrogen,  the  assumed  unit,  and  as  the  specific  gravities  specific 
are  merely  the  weights  of  equal  volumes,  the  numbers  in  the  column  f^vlties 
of  specific  gravities  and  those  in  the  column  of  weights  coincide.  3.  weights. 
The  identity  in  the  equivalent  volumes  of  the  elementary  gases, 
hydrogen,  nitrogen,  and  chlorine,  led  to  the  notion  that  the  equivalent 
volumes  of  most  other  elements  might  also  be  identical.  Assuming  specific 
that  identity,  the  specific  gravity,  for  example,  of  the  elements  gravity 
hydrogen,  carbon,  and  sulphur,  in  a gaseous  state,  may  easily  be  calculate  * 
calculated.  Thus,  taking  1,  6.12,  and  16.1  as  the  equivalents  of 
hydrogen,  carbon,  and  sulphur,  their  specific  gravities  in  the  gaseous 
state,  supposing  combining  volumes  equal,  will  be  in  the  same  ratio 
of  1,  6.12  and  16.1.  But  such  hypothetical  numbers  cannot  be 
always  confided  in  ; the  real  specific  gravity  of  a vapour  is,  in 
some  cases,  as  much  greater  than  the  hypothetical,  as  its  equivalent 
volume  is  less  than  that  of  hydrogen.^ 

129.  The  tables  supply  materials  for  calculating  the  specific  gra-  s^*jJcof 
vity  of  compound  gases,  and  of  verifying  the  accuracy  of  other  con-  compound 
elusions  respecting  their  composition.  The  specific  gravities  of  gases  cal- 
certain  gases  being  known,  together  with  their  uniting  proportions  culated' 
by  volumes,  and  the  resulting  volume,  we  can  easily  deduce  the 
weight  of  100  volumes  of  the  compound  gas  that  may  be  formed. 

130.  We  can  assume  the  specific  gravity  as  the  weight  of  100 
volumes,  or  the  weight  of  100  volumes  as  the  specific  gravity  when 
the  number  of  volumes  is  100  ; then  50  volumes  may  be  indicated  by 
one  half,  25  by  a fourth,  and  16.66  by  a sixth  of  the  specific  gravity 
of  100  volumes.  Thus  the  specific  gravity  of  hydrosulphuric  acid 
gas  will  be  that  of  its  constituents,  viz.  of  100  volumes  of  hydrogen 
-|-  £th  of  100  volumes  of  the  vapour  of  sulphur.! 

131.  As  vapours  are  easily  condensed  by  cold,  and  in  many  cases 
exist  as  such  only  at  high  temperatures,  their  specific  gravities  may 
often  be  obtained  by  calculation  more  accurately  than  by  experiment. 

132.  The  impracticability  of  contriving  convenient  names  expres- 
sive of  the  constitution  of  chemical  compounds,  suggested  the  em- 
ployment of  symbols  as  an  abbreviated  mode  of  denoting  the  compo- Chemical 
sition  of  bodies.  The  symbols  contrived  by  Berzelius  are  now  5m0j- 
extensively  used  by  chemists  and  mineralogists.  These  are  also 
called  chemical  formula,  and  it  is  important  that  the  chemical  stu- 
dent should  not  be  unacquainted  with  them.  The  following  table 
includes  the  symbols  of  the  elementary  substances  according  to 
Berzelius. 


♦The  identity  in  the  equivalent  volumes  of  hydrogen,  nitrogen,  and  chlorine,  sug- 
gested the  idea  that  the  atoms  of  all  the  elements  are  of  the  same  magnitude,  and 
equal  volumes  of  the  elements  in  a gaseous  state  were  supposed  to  contain  an  equal 
number  of  atoms.  The  late  researches  of  Dumas  and  Mitscherlich  have  shown  that 
this  is  not  the  fact.  t For  further  examples  see  Turner’s  Chemistry , 147. 


5 


34 


Attraction — Chemical. 


Chap.  I. 


TABLE  OF  SYMBOLS. 


Elements. 

Symb 

Elements. 

Symb. 

Elements. 

Symb. 

Aluminium 

Antimony  (Stibium) 

Arsenic 

Barium  - 

Bismuth 

Boron  - , 

Bromine 
Cadmium 
Calcium 
Carbon  - 
Cerium 
Chlorine  - 
Chromium  - 
Cobalt 

Columbium  (Tanta- 
lum) 

Copper  (Cuprum) 

Fluorine 

Glucinium 

A1 

Sb 

As 

Ba 

Bi 

B 

Br 

Cd 

Ca 

C 

Ce 

Cl 

Cr 

Co 

Ta 

Cu 

F 

G 

Gold  (Aurum) 
Hydrogen 
Iodine 
Iridium  - 
Iron  (ferrum) 

Lead  (Plumbum) 
Lithium 
Magnesium 
Manganese 
Mercury  (Hydrargy- 
rum) 

Molybdenum 
Nicae!  - 
Nitrogen 
Osmium  - 
Oxygen 
Palladium 
Phosphorus  - 
Platinum  - 

Au 

H 

I 

Ir 

Fe 

Pb 

L 

Mg 

Mn 

Hg 

Mo 

Ni 

N 

Os 

O 

Pd 

P 

Pt 

Potassium  (Kalium) 
Rhodium  - 
Selenium 
Silicium 

Silver  (Argentum) 
Sodium  (Natrium) 
Strontium  - 
Sulphur  - 
Tellurium  - 
Thorium  - 
Tin  (Stannum) 
Titanium 

Tungsten  (Wolfram) 
jUranium 
Vanadium 
Yrttrium 
Zinc 

| Zirconium  - 

K 

R 

Se 

Si 

n! 

Sr 

S 

Te 

Th 

Sn 

Ti 

W 

U 

V 

Y 
Zn 
Zr 

Explana-  The  foregoing  symbols  are  intended  to  represent  tbe  chemical 
equivalents  of  the  elements.  Thus,  the  letters  H,  I,  and  Ba,  stand 
for  one  equivalent  of  hydrogen,  iodine,  and  barium  ; and  2H,  3H, 
and  4H,  for  2,  3,  and  4 equivalents  of  hydrogen.  Two  equivalents 
of  an  element  are  often  denoted  by  placing  a dash  through,  or  more 
commonly  under  its  symbol : thus,  H means  2H,  and  P signifies 
2P.  Certain  compounds  are  often,  for  the  sake  of  brevity,  denoted 
by  single  symbols  in  the  same  manner  as  the  elements ; thus,  an 
equivalent  of  water,  ammonia,  and  cyanogen,  is  sometimes  expressed 
by  Aq,  Am,  and  Cy;  but  in  general  the  formulae  for  compound  bo- 
dies are  so  contrived  as  to  indicate  the  elements  they  contain,  and 
the  mode  in  which  they  are  united.  This  may  be  done  in  several 
ways ; but  that  which  first  suggests  itself,  is  to  connect  together  the 
symbols  by  the  same  signs  as  are  used  in  Algebra.  Thus  the  for- 
mula? K+O,  Ca+O,  Ba+O,  Mn+O,  Fe+O,  2Fe+30,  3H+N, 
2H+2C,  C+20,  N+50,  S+30,and  H+Cl,  denote  single  equiva- 
lents of  potassa,  lime,  baryta,  protoxide  of  manganese,  protoxide  of  iron, 
sesquioxide  of  iron,  ammonia,  olefiant  gas,  carbonic  acid,  nitric  acid, 
sulphuric  acid,  and  hydrochloric  acid.  The  formula  K-j-N-j-60  indi- 
cates the  elements  which  are  contained  in  an  equivalent  of  nitrate  of 
potassa : in  order  to  express  further  that  the  potassiu  m is  combined  with 
only  one  equivalent  of  oxygen,  the  remaining  oxygen  with  the  nitro- 
gen, and  the  potassa  with  nitric  acid,  the  symbols  are  placed  thus, — 
(K+0)+(N+50),  the  brackets  containing  the  symbols  of  those  ele- 
ments which  are  supposed  to  be  united.  A number  placed  on  the  out- 
side of  a bracket,  multiplies  the  compound  within  it:  thus  (K— (-0)— (- 
(S-(-30)  is  sulphate  of  potassa,  and  (K-|-0)-|-2(S-f-30)  is  the  bisul- 
phate. All  the  elements  contained  in  a compound  are  thus  visibly  re- 
presented, and  the  chemist  is  able  readily  to  trace  all  possible  modes  of 
combination,  and  to  select  that  which  is  most  in  harmony  with  the 


Chemical  Formula ?. 


35 


facts  and  principles  of  his  science.  He  may,  and  often  does,  thereby  Sect,  n. 
detect  relations  which  might  otherwise  have  escaped  notice. 

133.  Another  advantage  attributable  to  such  formulas  is,  that  they  Advantage 
facilitate  the  comprehension  of  chemical  changes,  If  hydrosulphuric  of  formulae, 
acid  acts  upon  the  protoxide  of  lead,  it  is  easy  to  say  that  the  sul- 
phur combines  with  the  lead,  and  the  hydrogen  with  the  oxygen  ; 

but  the  exact  adaptation  of  the  quantities  for  mutual  interchange 
appears  to  be  more  clearly  shown  by  symbols  than  by  a description 
or  a diagram.  In  the  simple  instance  alluded  to,  H-j-S  reacts  on 
Pb-f-O,  and  the  products  are  Pb-f-S  and  H-f-O.  When  hydrosul- 
phuric acid  acts  on  bicyanuret  of  mercury,  the  result  is  bisulphuret 
of  mercury  and  hydrocyanic  acid  ; the  substances  which  interchange 
elements  are2(H-j-S)  andHg-f-2Cy;  and  the  products  are  Hg-f-2S, 
and  2 (H-(-Cy).  In  more  complicated  changes  the  advantage  of  che- 
mical formulas  Is  still  more  manifest,  examples  of  which  kind  will  be 
found  in  other  parts  of  this  volume. 

134.  Useful  as  the  algebraic  chemical  formulae  are  for  the  purpose  of  Abbrevia- 
studying  chemical  changes,  they  are  sometimes  found  inconveniently  ted- 
long  where  the  object  is  merely  to  express  the  composition  of  bodies, 

and  accordingly  Berzelius  has  introduced  several  abbreviations.  For 
instance,  he  indicates  degrees  of  oxidation  by  dots  placed  over  the 

symbol,  writing  K,  C,  N,  instead  of  K-(-0,  C-j-20,  N-j-50,  for 
potassa,  carbonic  acid,  and  nitric  acid.  In  like  manner  he  denotes 

compounds  of  sulphur  by  commas,  writing  K,  Hg,  H instead  of  K-f-S, 

Hg-f-2S,  H-f-S,  for  sulphuret  of  potassium,  bisulphuret  of  mercury, 
and  hydrosulphuric  acid.  When  the  ratio  is  that  of  two  to  three 
he  employs  the  symbol  for  two  equivalents  above  stated  ; thus, 

Fe,  P,  As  is  used  instead  of  2Fe-f-30,  2P-|-50,  2As-)-50,  for  an 
equivalent  of  sesquioxide  of  iron,  phosphoric  acid,  and  arsenic  acid  ; 

and  similarly  we  have  As,  As  instead  of  2As-}-3S,  2As-j-5S  for  the 
sesquisulphuret  and  persulphuret  of  arsenic.  These  last  formulae 
are  sometimes  used  to  indicate  two  equivalents  instead  of  one  ; but 
as,  agreeably  to  the  atomic  theory,  the  smallest  possible  molecule  of 
sesquioxide  of  iron  consists  of  2 atoms  of  iron  and  3 of  oxygen,  the 
formula  2Fe-f-30  ought  to  stand  for  one  equivalent  only. 

Berzelius  often  dispenses  with  the  sign  -J-,  and  writes  combined 
elements  side  by  side,  the  sign  of  addition  being  understood  instead 

of  expressed.  Thus  he  uses  KS,  CaC,  BaN,  KS-f-NiS,  instead  of 

K+S,  Ca+C,  Ba+N,  (K+S)+(Ni+S),  for  sulphate  of  potassa, 
carbonate  of  lime,  nitrate  of  baryta,  and  the  double  sulphate  of 
potassa  and  oxide  of  nickel.  Two  or  more  equivalents  of  one  consti- 
tuent of  a compound  are  denoted  by  numbers  placed  in  the  same 
position  as  the  indices  of  powers  in  algebra : thus  NH3,  NC2, 

Fe2  H3  is  the  abbreviation  of  N-f-3H,  N-|-!2C,  2Fe-j-3H,  for  ammo- 
nia, cyanogen,  and  sesquihydrate  of  iron,  a compound  of  2 equiva- 


36 


Attraction — Chemical. 


Chap.  I. 


Isomeric 

bodies. 


Modes  of 
ascertain- 
ing the 
composi- 
tion of 
bodies. 


Ultimate 

and 


Proximate 

analysis. 


lents  of  sesquioxide  of  iron  and  3 of  water.  A number  used  before 
symbols,  like  coefficients  in  algebra,  multiplies  all  the  following 

symbols  not  separated  from  it  by  a -f-  sign.  Thus  in  8 Ca  Si3-|-K  Si6 
— j— 16  Aq  (which  is  the  formula  for  the  mineral  called  apophyllite), 

the  8 denotes  8 equivalents  of  Ca  Si3,  or  tersilicate  of  lime,  which 
are  united  with  1 equivalent  of  sexsilicate  of  potassa,  and  16  of 
water. 

Berzelius  also  expresses  the  vegetable  and  animal  acids  by  the 
first  letter  of  their  name,  with  a dash  over  it.  Thus  T,  A,  C,  B, 

G,  F,  are  the  symbols  for  tartaric,  acetic,  citric,  benzoic,  gallic,  and 
formic  acids. 

135.  It  was  formerly  thought  that  the  same  elements  united  in 
the  same  ratio  must  always  give  rise  to  the  same  compound  ; but 
examples  have  been  discovered  of  two  or  even  more  substances  con- 
taining the  same  elements  in  the  same  ratio,  and  yet  exhibiting 
chemical  properties  distinct  from  each  other.  For  such  compounds 
Berzelius  has  suggested  the  general  appellation  of  isomeric u from 
too;  equal , and  peqo ; part , expressive  of  equality  in  the  ingredients. 

Isomerism  is  quite  consistent  with  our  theories  of  chemical  union  ; 
insomuch  as  the  same  elements  may  be  grouped  or  combined  in  dif- 
ferent ways,  and  give  rise  to  compounds  essentially  distinct.* 

Some  bodies  consist  of  the  same  elements  in  the  same  ratio,  and 
yet  differ  in  their  equivalents.  The  nature  of  these  compounds  is  at 
once  detected  by  their  equivalents  being  unlike,  and  by  the  volume 
which  they  occupy  as  gases  compared  with  the  volumes  of  the  ele- 
ments of  which  they  consist.  Isomeric  bodies  of  this  kind  are  obvi- 
ously much  less  intimately  allied  than  those  above  described.  T.  153. 

136.  The  proof  which  establishes  the  nature  of  chemical  com- 
pounds, is  of  two  kinds,  synthesis  and  analysis . Synthesis  consists 
in  effecting  the  chemical  union  of  two  or  more  bodies  ; and  analysis, 
in  separating  them  from  each  other,  and  exhibiting  them  in  a sepa- 
rate state.  The  composition  of  sulphate  of  copper  (blue  vitriol)  is 
synthetically  demonstrated  by  uniting  sulphuric  acid  to  oxide  of 
copper.  When  we  have  a compound  of  two  or  more  ingredients, 
which  are  themselves  compounded  also,  the  separation  of  the  com- 
pounds from  each  other  may  be  called  the  proximate  analysis  of  the 
body ; and  the  farther  separation  of  these  compounds  into  their  most 
simple  principles,  its  ultimate  analysis. 

Thus  the  sulphuric  acid  of  the  sulphate  of  copper  consists  of  sul- 
phur and  oxygen,  and  oxide  of  copper  consists  of  copper  and  oxygen  ; 
consequently  we  should  say  that  the  ultimate  component  parts  of  blue 
vitriol  are  copper,  sulphur,  and  oxygen. 


♦Thus  the  elements  of  sulphate  of  potassa  may  perhaps  be  united  indiscriminately 
with  each  other,  as  expressed  by  the  formula  KSCM ; or  they  may  form  KO-f  SO3 ; or 
KS+O';  or  KO-H-SO2;  and  other  combinations  might  be  made.  The  second  of 
these  is  doubtless  the  real  one  ; but  no  one  can  say  that  the  others  are  impracticable. 
Again,  the  elements  of  peroxide  of  tin,  Sn  and  20,  may  either  form  SnO2,  or  SnO+O; 
and  those  of  the  sesquioxide  of  iron,  2Fe  and  30,  may  either  be  Fe203  or  FeO+FeOa, 
not  to  mention  other  possible  combinations-  The  elements  of  alcohol  are  2C,  3H,  and 
O,  which  may  be  united  indiscriminately  as  H3C20,  or  H^Cs-l-O,  or  as  H^-I-HO, 
besides  others  ; it  is  commonly  considered  a compound  of  olefiant  gas  and  water,  as 
indicated  by  the  last  formula.  T. 


Caloric. 


37 


The  proximate  analysis  of  sulphate  of  potassa  consists  in  resolving  Sect,  hi. 
it  into  potassa  and  sulphuric  acid ; and  its  ultimate  analysis  is 
effected  by  decomposing  the  potassa  into  potassium  and  oxygen,  and 
the  sulphuric  acid  into  oxygen  and  sulphur. 

When  the  analysis  of  any  substance  has  been  carried  as  far  as 
possible,  we  arrive  at  its  most  simple  principles  or  elements  ; by 
which  expression  we  are  to  understand,  not  a body  that  is  incapable 
of  further  decomposition,  but  only  one  which  has  not  yet  been  decom- 
posed. 


Section  III.  Heat  or  Caloric. 

137.  No  sensations  are  more  familiar  to  us  than  those  of  heat  Sens^ations^ 
and  cold.  They  are  excited  by  bodies  applied  to  our  organs,  and  at°old< 
different  times  very  different  degrees  of  sensation  are  excited  by  the 

same  body.  The  power  of  inducing  these  sensations  does  not  de- 
pend upon  the  matter  itself,  which  is  applied  to  our  organs  ; for  ev- 
ery shade  of  sensation  is  produced,  without  the  qualities  of  that 
matter  being  permanently  changed ; it  is  considered  as  depending 
on  the  operation  of  a certain  subtle  principle,  present  in  bodies,  and 
which,  according  to  its  quantity,  gives  rise  to  the  power  of  exciting 
different  sensations. 

138.  This  principle,  or  power,  has  been  distinguished  by  various  Has  receiv- 
appellations,  as  Fire,  Heat,  the  matter  of  Heat,  or  the  Igneous  fluid ; names!°US 
terms  which  are  either  ambiguous,  or  which  involve  some  hypothe- 
sis, and  which  are  superseded  by  the  unexceptionable  appellation  of 
Caloric,  m.  i.  183.* 

139.  Caloric,  so  far  as  its  chemical  agencies  are  concerned,  mayMaybe 
be  chiefly  considered  under  two  views — as  an  antagonist  to  the  co“  under  two 
hesive  attraction  of  bodies — and  as  concurring  with,  and  increasing  views, 
elasticity.  By  removing  the  particles  of  any  solid  to  a greater  dis- 
tance, from  each  other,  their  cohesive  attraction  is  diminished ; and 

one  of  the  principal  impediments  to  their  union  with  other  bodies  is 
overcome.  On  the  other  hand,  caloric  may  be  infused  into  bodies 
in  such  quantity,  as  not  only  to  overcome  cohesion,  but  to  place  their 
particles  beyond  the  sphere  of  chemical  affinity. 

In  many  cases,  when  two  bodies  are  combined  together,  one  of 
which  is  fixed,  and  the  other  becomes  elastic  by  union  with  caloric, 
we  are  able,  by  its  interposition  alone,  to  effect  their  disunion.  Thus 
carbonate  of  lime  gives  up  its  carbonic  acid  by  the  mere  applica- 
tion of  heat. 

140.  We  may  consider,  then,  all  bodies  in  nature  as  subject  to  The  state 
the  action  of  two  opposite  forces,  the  mutual  attraction  of  their  par-  £fflE25iced 
tides  on  the  one  hand,  and  the  repulsive  power  of  caloric  on  the  by  caloric, 
other  ; and  bodies  exist  in  the  solid,  liquid,  or  elastic  state,  as  one  or 

the  other  of  these  forces  prevails. 

Water,  by  losing  caloric,  has  its  cohesion  so  much  increased,  that  it  assumes 
the  solid  form  of  ice;  adding  caloric,  we  diminish  again  its  cohesion,  and  render 
it  fluid;  and  finally,  by  a still  farther  addition  of  caloric,  we  change  it  into  va- 


* Or  we  may  define  caloric  as  the  agent  to  which  the  phenomena  of  heat  and  com- 
bustion are  ascribed.  U. 


38 


Caloric — Expansion . 


Chap.  I. 


It  expands 
bodies. 


Prored  by 
experi- 
ments. 


Principle 
upon  which 
pyrometers 
are  made. 
Expansion 
of  solids. 


pour,  and  give  it  so  much  elasticity,  that  it  may  be  rendered  capable  of  bursting 
' the  strongest  vessels.  In  many  liquids,  the  tendency  to  elasticity  is  even  so 
great,  that  they  pass  to  the  gaseous  form  by  the  mere  removal  of  the  weight  of 
the  atmosphere  ; as  is  the  case  with  ether  in  the  exhausted  receiver  of  the  air 
pump. 

141.  Expansion  is  the  most  obvious  and  familiar  effect  of  caloric 
and  it  takes  place,  though  in  different  degrees,  in  all  forms  of  mat- 
ter. When  a body  which  occasions  the  sensation  of  heat  on  our 
organs,  is  brought  into  contact  with  another  body  which  has  no  such 
effect,  the  result  of  their  mutual  action  is  that  the  hot  body  contracts, 
and  loses  to  a certain  extent  its  power  of  communicating  heat,  and 
the  other  body  expands,  and  in  a degree  acquires  this  power. 

The  expansion  of  solids  may  be  made  apparent  by  heating  a rod  of  iron, 
of  such  a length  as  to  be  included,  when  cold,  between  two  points,  and 
the  diameter  of  which  is  such,  as  barely  to  allow  it  to  pass  into  an  iron  ring. 
When  heated,  it  will  have  become  sensibly  larger ; and  it  will  be  found  incapa- 
ble of  passing  through  the  ring. 

142.  This  property  of  metals  has  been  applied  to  the  construction 
of  an  instrument  for  measuring  temperature,  called  a pyrometer .* 

143.  The  expansion  of  solids  has  engaged  the  attention  of  sever- 
al experimenters, t and  the  following  results  have  been  obtained  : — 
I.  Different  solids  do  not  expand  to  the  same  degree  from  equal  ad- 
ditions of  heat.  2.  A body  which  has  been  heated  from  the  tem- 
perature of  freezing  to  that  of  boiling  water,  and  again  allowed  to 
cool  to  32°  F.,  recovers  precisely  the  same  volume  which  it  posses- 
sed at  first.  3.  The  dilatation  of  the  more  permanent  or  infusible 
solids  is  very  uniform  within  certain  limits ; their  expansion,  for  ex- 


Danlcll'*  py- 
roin«tir. 


* Au  instrument  of  this  kind  is  repre- 
rcsented  by  fig.  22,  which  will  be  found 
very  convenient  for  showing  the  expansi- 
bilities of  bars  of  different  metals,  at  tem- 
peratures not  exceeding  that  of  boiling 
water.  Upon  a flat  piece  of  mahogany 
are  tixed  brass  studs,  g g,  ou  which  the 
metallic  bar,y  f is  placed.  One  end  of  „ , r 
this  bar  bears  against  a lever  b at  a point  , 
very  near  its  fulcrum;  the  other  end  of  / {*«= 

this  lever,  which  is  bent,  bears  against 
another  lever  c,  the  lower  extremity  of 
which  is  an  index.  Beneath  this  index  is  a graduated  arc  d.  When  we  wish  to  immerse 
the  bar  in  hot  water,  or  to  apply  heat  gradually  through  the  medium  of  water,  the 
bar  is  passed  through  the  brass  box  a,  which  has  an  aperture  at  each  end.  An  open- 
ing is  left  in  the  board  immediately  under  the  box,  to  allow  the  application  of  a lamp. 
The  small  expansion  of  the  metallic  bar  is  magnified  by  the  first  lever  in  the  pro- 
portion of  the  distances  of  the  point  of  pressure  from  its  plane,  and  from  its  other 
extremity ; and  this  magnified  effect  is  again  magnified  by  the  other  lever,  so  that  an 
expansion  of  the  tooth  part  of  an  inch  corresponds  to  a whole  inch  on  the  scale. 
This  pyrometer  is  liable  to  the  objection  that  the  distance  of  the  points  of  pressure 
from  the  fulcrum  and  extremity  of  each  lever  is  variable  during  the  experiment.  ( See 
Ferguson’s  Led.) 

Daniell’s  pyrometer  is  susceptible  of  great  precision.  Its  indications  result  from  a 
difference  in  the  expansion  and  contraction  of  a platinum  bar.  and  a tube  of  black 
lead  ware,  in  which  it  is  contained.  These  differences  are  made  available  by  con- 
necting an  index  with  the  platinum  bar,  which  traverses  a circular  scale  fixed  on  to 
the  tube.  See  a description  of  this  instrument  in  Turner's  Elements  p.  26,  Quart. 
Jour  of  Sd.  xi.  309,  and  PhUos.  Trans.  1330-1. 


t The  Philosophical  Transactions  contain  various  dissertations  on  the  subject  by  El- 
licot,  Smeaton,  Troughton,  aud  General  Roy;  and  M.  Biot, in  his  Trade  de  Physiaue , 
ha«  given  the  results  of  experiments  performed  with  great  care  by  Lavoisier  and  La- 
place. 


39 


Relative  Expansibilities  of  Liquids . 


ample,  from  the  freezing  point  of  water  to  122°,  is  equal  to  what 
takes  place  betwixt  122°  and  212°.  The  subsequent  researches  of 
Dulong  and  Petit, ^ prove  that  solids  do  not  dilate  uniformly  at  high 
temperatures,  but  expand  in  an  increasing  ratio  ; that  is,  the  higher 
the  temperature  beyond  212°  the  greater  the  expansion  for  equal 
additions  of  heat.  It  is  manifest,  indeed,  from  their  experiments, 
that  the  rate  of  expansion  is  an  increasing  one  even  between  32° 
and  212°  ; but  the  differences  which  exist  within  this  small  range 
are  so  inconsiderable  as  to  escape  observation,  and,  therefore,  for 
most  practical  purposes  may  be  disregarded. 

The  subjoined  table  includes  the  most  interesting  results  of  La- 
voisier and  and  Laplace.  (Biot,  vol.  1.  p.  158.) 

Names  of  Substances . Elongation  when  heated 

from  32°  to  212° 


TiV&  its  length. 

T2"Vb 

5^T 

5ih- 

1 

FT¥ 

¥T2- 

3^7 

1 

8TTT 

1 

SSI 

5TB 

¥T2 

BTT2 

TT5T 


Glass  tube  without  lead,  a mean 
of  three  specimens 
English  flint  glass  - 

Copper  - 

Brass — mean  of  two  specimens 
Soft  iron  forged 
Iron  wire  - 

Untempered  steel  - ' 

Tempered  steel  - 

Lead  - - 

Tin  of  India  - 

Tin  of  Falmouth  - 

Silver  - - 

Gold — mean  of  three  specimens 
Platinum,  determined  by  Borda 

144.  The  expansion  of  liquids  is  seen  by  putting  a common 
thermometer,  made  with  mercury  or  alcohol,  into  warm  water, 

Fig.  23,  when  the  dilatation  of  the  liquid  will  be  shown  by 
its  ascent  in  the  stem.  The  experiment  is  indeed  illustrative 
of  two  other  facts.  It  proves,  first  that  the  dilatation  increas- 
es with  the  temperature  ; for  if  the  thermometer  be  plunged 
into  several  portions  of  water  heated  to  different  degrees, 
the  ascent  will  be  greatest  in  the  hottest  water,  and  least  in 
the  coolest  portions.  It  demonstrates,  secondly,  that  liquids 
more  than  solids.  The  glass  bulb  of  the  thermometer  is  itself  ex- 
panded by  the  hot  water,  and,  therefore,  is  enabled  to  contain  more 
mercury  than  before ; but  the  mercury  being  dilated  to  a much 
greater  extent,  not  only  occupies  the  additional  space  in  the  bulb, 
but  likewise  rises  in  the  stem.  Its  ascent  marks  the  difference  be- 
tween its  own  dilatation  and  that  of  the  glass,  and  is  only  the  ap- 
parent, not  the  actual,  expansion  of  the  liquid. 

145.  Liquids  differ  also  in  their  relative  expansibilities : ether  is 
more  expansible  than  spirit  of  wine,  and  spirit  more  than  water,  and 
water  more  than  mercury.  Those  liquids  are  generally  most  ex- 
pansible which  boil  at  the  lowest  temperature. 


Fig.  23. 


expand 


Sect.  hi. 


Of  liquids, 


Their  rela 
tive  expan- 
sibilities 
different. 


* An.  de.  Ckim.  et  de  Phys.  vn» 


40 


Caloric. 


Chap.  I. 


Of  mercu- 
ry, 


Liquids  ex- 
pand in  in- 
creasing 
ratio. 


This  may  be  rendered  evident  by  partially  filling  several  glass  tubes  of  equal 
diameters,  furnished  with  bulbs,  with  the  different  liquids,  and  placing  them  in 
hot  water;  as  the  liquids  expand,  they  will  rise  to  different  heights  in  the  tubes. 
To  render  this  more  apparent  the  liquids  may  be  tinged  with  some  colouring 
matter.  The  tubes  may  be  placed  in  a light  frame,  having  a thin  copper  trough 
to  contain  water,  which  may  be  heated  by  a lamp.  Fig.  24.  Or  they  may  be 
suspended  as  in  Fig.  25. 

F‘g-24.  Fig.  25. 


146.  From  the  frequency  with  which  mercury  is  employed  in  phi- 
losophical experiments,  it  is  important  to  know  the  exact  amount  of 
its  expansion.  This  subject  has  been  investigated  by  several  phi- 
losophers, but  the  experiments  of  Lavoisier  and  Laplace,  and  espe- 
cially of  Dulong  and  Petit,  are  entitled  to  the  greatest  confidence. 
According  to  the  former,  the  actual  dilatation  of  mercury,  in  pas- 
sing from  the  freezing  to  the  boiling  point  of  water,  amounts  to 

of  its  volume ; but  the  result  obtained  by  Dulong  and  Petit, 
who  found  it,  -&VV?r  is  probably  still  nearer  the  truth.  Adopting 
the  last  estimate,  this  metal  dilates,  for  every  degree  of  Fahrenheit’s 
thermometer,  of  the  bulk  which  it  occupied  at  the  temperature 
of  32°.  If  the  barometer,  for  instance,  stand  at  30  inches  when  the 
thermometer  is  at  32°,  we  may  calculate  what  its  elevation  ought  to 
be  when  the  latter  is  at  60°,  or  at  any  other  temperature.  The  ap- 
parent expansion  of  mercury  contained  in  glass  is  of  course  less 
than  the  absolute  expansion.* 

147.  All  experimenters  agree  that  liquids  expand  in  an  increasing 
ratio,  or  that  equal  increments  of  heat  cause  a greater  dilatation  at 
high  than  at  low  temperatures.  Thus,  if  a fluid  is  heated  from  32° 
to  122°,  it  will  not  expand  so  much  as  it  would  do  in  being  heated 
from  122°  to  212°,  though  an  equal  number  of  degrees  is  added  in 
both  cases.  The  nearer  a liquid  approaches  its  boiling  point,  the 
greater  is  its  expansibility;  hence  those  liquids  appear  most  equably 
expansible  which  have  the  highest  boiling  points,  and  hence  one  of 
the  great  advantages  of  mercury  in  constructing  thermometers. 


* Between  the  limits  of  32°  and  212°  F.  Lavoisier  and  Laplace  estimate  the  apparent 

expansion  at  5*3  and  Dulong  and  Petit  at  f of  its  volume,  being  TT55T  lor  each 
degree  of  Fahrenheit's  thermometer.  Dulong  and  Petit  state,  that  the  mean 

total  expansion  of  mercury  from  32°  to  572°  F.  for  each  degree  is  9-5*3 ny  ; and  that 
the  mean  apparent  expansion  in  glass  from  32°  to  572°  F.  for  each  degree  is 
The  temperature  in  tneir  experiments  was  estimated  by  an  air  thermometer,  which 
they  consider  more  uniform  in  its  rate  of  expansion  than  one  of  mercury.  The  tem- 
perature of  572°  F.  on  the  air  thermometer  corresponds  to  536°  in  the  mercurial 
one.  T.  19. 


41 


Dilatation  of  Mr. 

148.  The  expansion  of  air  may  be  shown  by  inverting  a tube  sect._ni; 
terminated  by  a bulb,  and  partly  filled  with  water  (Fig.  26);  the 
air  confined  in  the  bulb  will  expand  when  heated,  and  expel  the 
water  from  the  tube. 

Fig.  26.  Fig.  27. 


Specific 

gravity  al- 

149.  As  heat  increases  the  bulk  of  all  bodies,  it  is  obvious  thatj,ehr^g^ 
change  of  temperature  is  constantly  producing  changes  in  their  den-tempera- 
sity  or  specific  gravity,  as  may  be  easily  demonstrated  in  fluids  where  ture> 
there  is  freedom  of  motion  among  the  particles.  If  we  apply  heat  to  Of  liquids, 
the  bottom  of  a vessel  of  water,  that  portion  of  the  fluid,  which  is 
nearest  to  the  source  of  heat,  is  expanded,  and  becoming  specifically 
lighter,  ascends,  and  is  replaced  by  a colder  portion  from  above. 

This,  in  its  turn,  becomes  heated  and  dilated,  and  gives  way  to  a 
second  colder  portion  ; and  thus  the  process  goes  on,  as  long  as  the 
fluid  is  capable  of  imbibing  heat.  (Fig.  27.  ) 

150.  In  air,  similar  currents  are  continually  pro- 
duced, and  the  vibratory  motion  observed  over  chim- 
ney pots,  and  slated  roofs  which  have  been  heated 
by  the  sun,  depends  upon  this  circumstance':  the 
warm  air  rises,  and  its  refracting  power  being  less 
than  that  -of  the  circumambient  colder  air,  the  cur- 
rents are  rendered  visible  by  the  distortion  of  objects 
viewed  through  them.  This  is  easily  illustrated  by 
placing  a spiral  of  pasteboard  upon  a wire  over  an 
Argand  lamp,  or  at  the  side  of  a stove  pipe.^ 

The  ventilation  of  rooms  and  buildings  can 
only  be  perfectly  effected  by  suffering  the  heated  and 
foul  air  to  pass  off  through  apertures  in  the  ceiling, 
while  fresh  air,  of  any  desired  temperature,  is  ad- 
mitted from  below. t 

151.  As  the  particles  of  air  and  aeriform  substances -are  not  held 
together  by  cohesion,  they  are  found  to  dilate  from  equal  additions 
of  heat  much  more  than  solids  or  liquids.  Now, 'chemists  are  in  the 
habit  of  estimating  the  quantity  of  the  gases  employed  in  their  expe- 
riments by  measuring  them  ; and  since  the  volume  occupied  by  any 


* Advantage  is  taken  of  this  in  heating  apartments  by  furnaces  placed  in  cellars. 
Cold  air  being  brought  in  contact  with  the  surface  of  heated  metal,  and  allowed  to  as- 
cend through  pipes  into  the  apartments. 

t Various  contrivances  have  been  resorted  to,  to  prevent  the  passage  of  cold  air 
from  above  downwards  through  the  ventilator,  which  can  only  be  completely  eflected 
by  keeping  the  ventilating  tubes  at  a higher  temperature  than  the  surrounding  air ; 
heating  them,  for  instance,  by  steam  ; passing  them  through  a fire ; or  placing  a lamp 
beneath  them,  of  sufficient  dimensions  to  cause  a strong  current  upwards. 

6 


Of  air, 

Fig.  28. 


42 


Caloric . 


Chap  I. 


Peculiar  ef- 
fect of  heat. 


gas  is  so  much  influenced  by  temperature,  it  is  essential  to  accuracy 
that  a due  correction  be  made  for  the  variations  arising  from  this 
cause  ; that  they  should  know  how  much  dilatation  is  produced 
by  each  degree  of  the  thermometer,  whether  the  rate  of  expansion  is 
uniform  at  all  temperatures,  and  whether  that  ratio  is  the  same  in  all 
gases. 

152.  All  gases  undergo  equal  expansions  by  the  same  addition  of 
heat,  supposing  them  placed  under  the  same  circumstances  ; so  that  it 
is  sufficient  to  ascertain  the  law  of  expansion  observed  by  any  one 
gas,  in  order  to  know  the  law  for  all.* 

153.  There  is  a peculiarity  in  the  effect  of  heat  upon  the  bulk  of 
some  fluids,  namely,  that  at  a certain  temperature,  increase  of  heat 
causes  them  to  contract,  and  its  diminution  makes  them  expand. 
This  singular  exception  is  only  observable  in  those  liquids  which  ac- 
quire an  increase  of  bulk  in  passing  from  the  liquid  to  the  solid 
state,  and  is  remarked  only  within  a few  degrees  of  temperature 
above  their  point  of  congelation.  Water  is  a noted  example  of  it. 
Ice  swims  upon  the  surface  of  water,  and,  therefore,  must  be 
lighter  than  it,  which  is  a convincing  proof  that  water,  at  the  mo- 
ment of  freezing,  must  expand.  The  increase  is  estimated  by  Boyle 
at  about  £th  of  its  volume,  which  gives  900  as  the  specific  gravity 


♦It  appears  from  the  experiments  of  Gay  Lussac,  that  100  parts  of  air,  in  being  heat- 
ed from  32°  to  212°  F.,  expand  to  137.6  parts.  The  increase  for  ISO  degrees  is, 

therefore,  0 376  or  'W&ths  of  its  bulk  : and  by  dividing  this  number  by  160,  it  is  found 
that  a given  quantity  of  dry  uir  dilates  to  ninth  of  the  volume  it  occupied  at  32°,  for 
every  degree  of  Fahrenheit’s  thermometer. 

This  point  being  established,  it  is  easv  to  ascertain  what  volume  any  given  quantity 
of  gas  should  occupy  at  any  given  temperature.  Suppose  a certain  portion  of  gas  to 
occupy  20  measures  of  a graduated  tube  at  32°,  it  may  be  desirable  to  determine  what 

would  be  its  bulk  at  42°.  For  every  degree  of  heat  it  has  increased  by  T^oth  of  its 
original  volume,  and,  therefore,  since  the  increase  amounts  to  ten  degrees,  the  20 
measures  will  have  dilated  hy  jV^jths.  The  expression  will,  therefore,  be  20+20  xjVo 
=20.416.  It  must  not  be  forgotten  that  the  volume  which  the  gas  occupies  at  32°  is 
a necessary  element  in  all  such  calculations.  Thus,  having  20.416  measures  of 
gas  at  42°,  the  corresponding  bulk  for  62°  cannot  be  calculated  by  the  formula 
20.4 1 6+20.1 1 6 ; the  real  expression  is  20+20. 4l6y1£°(jl  because  the  increase 
is  only  ^S&ths  of  the  space  occupied  at  32°,  which  is  20  measures.* 

A similar  remark  applies  to  the  formula  for  estimating  the  effect  of  beat  on  the  height 
of  the  barometer. 

The  rate  of  expansion  of  atmospheric  air  at  temperatures  exceeding  212  has  been 
examined  by  Dulong  and  Petit,  and  the  following  table  contains  the  result  o*  their  ob- 
servations. (An.  de  Ch.  el  de  Ph.  vii.  120.) 


Temperature  by  the  Mercurial 
Thermometer. 

Corresponding 
volumes  of  a 
given  volume 
of  air. 

Fahrenheit. 

Centigrade. 

— 33 

— 36 

0 8650 

32 

0 

1.0000 

212 

100 

1.3750 

302 

160 

1.6576 

392 

200 

1.7389 

462 

250 

1.8189 

672 

300 

2.0976 

Mercury  boils  630 

360 

2.3125 

* See  Formula,  Turner,  21. 


Temperature. 


43 


of  ice,  that  of  water  being  1000.*  Dalton  estimates  the  specific  gra-  Sect  m. 
vity  of  ice  at  9.42.  Water  has  attained  its  maximum  of  density  at  Water,  its 
about  39°t,  and  if  it  be  cooled  below  39°  it  expands  as  the  tempera-  maximum 
ture  diminishes,  as  it  does  when  heated  above  that  point. 

Immerse  two  thermometer  tubes,  one  containing  spirits  of  wine  and  the  other  Exp. 
water,  into  melting  snow  ; the  former  will  sink  till  it  indicates  32°  F.,  but  the 
latter,  when  it  has  nearly  attained  39°  F.,  will  begin  to  expand,  and  continue  to 
do  so  till  it  freezes.  Or,  fill  a flask  capable  of  holding  three  or  four  ounces,  with 
water  at  the  temperature  of  60°  F.  and  adapt  a cork  to  it,  through  which  passes  a 
glass  tube  open  at  both  ends,  about  the  eighth  of  an  inch  wide,  and  ten  inches 
long.  After  having  filled  the  flask,  insert  the  cork  and  tube,  and  pour  a little  wa- 
ter into  the  latter  till  the  liquid  rises  to  the  middle  of  it.  On  immersing  the  flask 
in  a mixture  of  pounded  ice  and  salt,  the  water  will  fall  in  the  tube,  marking  con- 
traction ; but  in  a short  time  an  opposite  movement  will  be  perceived,  indicating 
that  expansion  is  taking  place,  while  the  water  within  the  flask  is  at  the  same 
time  yielding  caloric  to  the  freezing  mixture  on  the  outside  of  it. 

This  anomaly  in  respect  to  water  is  productive  of  very  important  ^5*55!^ 
consequences,  in  preserving  the  depths  of  rivers  and  lakes  of  a tern- in this J 
perature  congenial  to  their  inhabitants.  anomaly. 

154.  The  most  remarkable  circumstance  attending  this  expansion, 

is  the  prodigious  force  with  which  it  is  effected.  Boyle  filled  a brass  L 
tube,  three  inches  in  diameter,  with  water,  and  confined  it  by  means 
of  a moveable  plug ; the  expansion,  when  it  froze,  took  place  with 
such  violence  as  to  push  out  the  plug,  though  preserved  in  its  situa- 
tion by  a weight  equal  to  74  pounds.  The  Florentine  Academicians 
burst  a hollow  brass  globe,  whose  cavity  was  only  an  inch  in  diame- 
ter, by  freezing  the  water  with  which  it  was  filled  ; and  it  has  been 
estimated  that  the  expansive  power  necessary  to  produce  such  an 
effect  was  equal  to  a pressure  of  27,720  pounds  weight.  Major 
Williams  gave  ample  confirmation  of  the  same  fact  by  some  experi- 
ments which  he  performed  at  Quebec  in  the  years  1784  and  17854 
Glass  bottles,  lead  and  iron  pipes,  &c.,  in  which  water  freezes,  are 
often  ruptured. 

155.  Water  is  not  the  only  liquid  which  expands  under  reduction  Other 
of  temperature,  as  the  same  effect  has  been  observed  in  a few  others  cases> 
which  assume  a highly  crystalline  structure  on  becoming  solid  : — 
fused  iron,  antimony,  zinc,  and  bismuth  are  examples  of  it.  Mer- 
cury is  a remarkable  instance  of  the  reverse ; for  when  it  freezes,  it 
suffers  a very  great  contraction  (31  note.) 

156.  The  cause  of  the  expansion  of  water  at  the  moment  of  freez-  Cause, 
ing  is  attributed  to  a new  and  peculiar  arrangement  of  its  particles. 

Ice  is  in  reality  crystallized  water,  and  during  its  formation  the  par- 
ticles arrange  themselves  in  ranks  and  lines,  which  cross  each  other 
at  angles  of  60°  and  120°,  and  consequently  occupy  more  space  than 
when  liquid.  This  may  be  seen  by  examining  the  surface  of  water 
while  freezing  in  a saucer.  No  very  satisfactory  reason  can  be  as- 
signed for  the  expansion  which  takes  place  previous  to  congelation. 

157.  The  state  of  a body  with  respect  to  its  power  of  producing  Tempera- 
the  effects  which  arise  from  the  operation  of  caloric,  is  termed  its  ture 


* Experiments  on  Cold. 

t Hallstrom  An.  de  Chim.  et  Phys.  xxviii,  90,  whose  experiments  were  made  with 
great  care.  According  to  the  more  recent  experiments  of  Stampfer  38.75  and  to  those 
of  Crichton  38-97.  Johnston’s  Report  in  1st  Report  of  the  British  Association- 
t Phil.  Trans.  Ed.  ii,  23. 


44 


Caloric. 


Principle 
on  which 
the  ther- 
mometer 
indicates 
tempera- 
ture. 


Thermom- 

eter. 


Chap,  i.  temperature.  In  every  body  the  temperature  depends  on  the  quan- 
tity of  caloric  which  it  contains,  and  the  temperature  is  said  to  be 
high  or  low  as  it  respects  another  body,  in  proportion  as  it  occasions 
an  expansion  or  contraction  of  its  parts. 
kmfvvneCtly  temPerature  bodies  can  be  but  imperfectly  estimated 

from sensa- b>y  the  sensation  of  heat  or  cold  they  produce,  the  sensation  being 
tion.  modified  by  preceding  impressions  upon  the  sentient  organ  and  other 
external  circumstances.  Hence  the  necessity  of  some  common 
measure  of  temperature,  as  by  means  of  the  Thermometer . 

159.  The  principle  on  which  the  thermometer  indicates  tempera- 
ture, is,  that  caloric  has  a tendency  always  to  preserve  an  equilibri- 
um ; so  that  if  two  bodies  at  different  temperatures,  be  brought  into 
contact,  it  will  pass  from  the  one  at  the  higher  into  that  at  the  lower 
temperature,  until  the  temperature  of  both  is  the  same.  Thus,  if 
we  mix  equal  quantities  of  the  same  fluid  at  different  temperatures, 
the  cold  portion  will  expand  as  much  as  the  hot  portion  contracts, 
and  the  resulting  temperature  is  the  mean  ; so  that  it  appears,  that 
as  much  heat  as  is  lost  by  the  one  portion  is  gained  by  the  other. 

160.  A common  thermometer  consists  of  a tube  terminated  at  one 
end  by  a bulb,  and  hermetically  closed  at  the  other.  The  bulb  and 
part  of  the  tube  are  filled  with  an  appropriate  liquid,  which  when 
designed  to  measure  very  low  temperatures,  is  spirit  of  wine; 
under  other  circumstances  quicksilver  is  better  adapted  for  the 
purpose.*  A graduated  scalet  is  attached  to  the  stem ; and 
whenever  the  instrument  is  applied  to  bodies  of  a higher  tempera- 
ture, the  mercury  or  spirit  expands  and  rises  in  the  lube. 

161.  In  dividing  the  scale  of  a thermometer,  the  two  fixed  points 
usually  resorted  to  are  the  freezing  and  boiling  of  water,  which  al- 
ways take  place  at  the  same  temperature,  when  under  the  same  at- 
mospheric pressure.  The  intermediate  part  of  the  scale  is  divided 
into  any  convenient  number  of  degrees ; and  it  is  obvious,  that 
all  thermometers  thus  constructed  will  indicate  the  same  degree 
of  heat  when  exposed  to  the  same  temperature.  In  the  centigrade 
thermometer,  this  space  is  divided  into  100°  ; the  freezing  of  water 
being  marked  0°,  the  boiling  point  100°.  In  this  country  we  use 
Fahrenheit’s  scale  of  which  the  0°  is  placed  at  32°  below  the  freez- 
ing of  water,  which,  therefore,  is  marked  32°,  and  the  boiling  point 
212°,  the  intermediate  space  being  divided  into  180°.  Another  scale 
is  Reaumur’s  ; the  freezing  point  is  0°,  the  boiling  point  80°.  These 
nre  the  principal  thermometers  used  in  Europe  and  this  country.! 


Gradua- 

tion. 


* Quicksilver  will  indicate  500°  F.  but  freezes  at  — 39°. 
t As  the  chemist  will  often  have  occasion  to  employ  the  thermometer  for  as- 
certaining the  temperature  of  corrosive  liquids,  tne  graduated  scale  should 
be  provided  with  a hinge,  so  as  to  double  back,  and  leave  the  bulb  exposed, 
as  shown  in  Fig.  29. 

t For  the  method  of  constructing  thermometers  sec  Faraday’s  Manipu- 
lation and  for  those  of  great  sensibility,  Quart.  Jour,  of  Sd - vii-  p.  183. 


Fig.  29i 


Thermometers . 45 

162.  Each  degree  of  Fahrenheit’s  scale  is  equal’to  fths  of  a degree  Sect,  hi. 

on  Reaumur’s  : if,  therefore,  the  number  of  degrees  on  Fahrenheit’s  Rules  for 
scale  above  or  below  the  freezing  of  water  be  multiplied  by  4 and 
divided  by  9,  the  quotient  will  be  the  corresponding  degree  ofryther- 
Reaumur.  mometers. 

Fahrenheit.  Reaumur. 

68°— 32°=  36X4=144-7-9—16° 

2 1 2°— 32°=  1 80  X 4=720-^-9=80°* 

163.  M.  Bellain  has  observed  that  mercurial  thermometers  slowly  Change  of 
change  their  point  of  zero,  which  uniformly  becomes  higher  than  at^ero’ 

the  time  of  graduation.  This  phenomenon  appears  owing  to  a di- 
minished capacity  of  the  bulb  due  to  the  atmosphere  continually 
pressing  on  its  exterior,  while  a vacuum  exists  in  the  interior  of  the 
tube  ; for  it  has  not  been  noticed  either  in  mercurial  thermometers 
which  are  unsealed,  or  in  thermometers  made  with  alcohol.  The 
principal  contraction  ensues  soon  after  the  tube  is  sealed,  and  hence 
some  months  should  be  permitted  to  elapse  between  the  sealing  and 
graduation  of  a thermometer.! 

164.  Air  is  sometimes  resorted  to  as  indicating  very  small  Air  ther- 
chang.es  of  temperature.  The  instrument  employed  by  Sane- mometers’ 
torio,  to  whom  the  invention  of  the  thermometer  is  generally 
ascribed,  was  of  a very  simple  kind,  and  measured  variations 

of  temperature  by  the  variable  expansion  of  a confined  portion 

* To  reduce  the  degrees  of  Reaumur  to  those  of  Fahrenheit,  they  are  to  be  multi- 
plied by  9,  and  divided  by  4. 

Reaumur.  Fahrenheit. 

1 6°  X 9= 144-^4=  36°+32°=  68 
80°X9=720-h4=180°+32°=212 

Every  degree  of  Fahrenheit’s  is  equal  to  fths  of  a degree  on  the  centigrade  scale ; 
the  reduction  therefore  is  as  follows : 

Fahrenheit.  Centigrade. 

212—32=180X5=900^-9=100° 

Centigrade.  Fahrenheit. 

100X9=900-7-5=180+32=212° 


Corresponding 

degrees 


Fahr. 

Cent. 

Reaum. 

Fahr. 

Cent. 

Reaum. 

Fahr. 

Cent. 

Reaum. 

212 

100 

80 

113 

45 

36 

14 

-10 

- 8 

203 

95 

76 

104 

40 

32 

5 

-15 

-12 

194 

90 

72 

95 

35 

23 

- 4 

-20 

-16 

185 

85 

68 

86 

30 

24 

-13 

-25 

-20 

176 

80 

64 

77 

25 

20 

-22 

-30 

-24 

167 

75 

60 

68 

20 

16 

-31 

-35 

-28 

158 

70 

56 

59 

15 

12 

-40 

-40 

-32 

149 

65 

52 

50 

10 

8 

140 

60 

48 

41 

5 

4 

131! 

55 

44 

32 

0 

0 

122| 

50 

40 

23 

-5 

-4 

f An.  de.  Ch.  et  de  Ph.  xxi.  330. 


46 


Caloric. 


Chap.  I. 


Advanta- 
ges of. 


Leslie’s. 


Howard's. 


O 


pair 


. of  air.  This  instrument  is  represented  in  the  margin.  It  consists 
of  a glass  tube,  eighteen  inches  long,  open  at  one  end,  and*Fig.3o. 
blown  into  a ball  at  the  other.  If  a warm  hand  be  applied 
to  the  ball,  the  included  air  will  expand,  and  a portion  be  ex* 
pelled  through  the  open  end  of  the  tube.  And  if  in  this  state 
the  aperture  is  quickly  immersed  in  a cup  filled  with  some 
coloured  liquid,  it  will  ascend  in  the  tube,  as  the  air  in  the  ball 
contracts  by  cooling;  and  its  altitude  will  in  every  case  depend 
upon  the  degree  of  expansion  which  the  air  has  previously 
undergone.  In  this  manner  it  is  prepared  for  use,  and  will 
indicate  increase  of  temperature  by  the  descent  of  its  fluid, 
and  vice  versa.  These  effects  may  be  exhibited,  alternately 
by  applying  the  hand  to  the  ball,  and  then  blowing  on  it  with 
of  bellows.  The  amount  of  the  expansion  or  contraction  is  measur 
ed  by  a graduated  scale  attached  to  the  stem  of  the  instrument. 

165.  The  advantages  of  the  Air  Thermometer  consist  in  the  great 
amount  of  the  expansion  of  air,  when  compared  with  that  of  any 
liquid;  by  which  it  is  enabled  to  detect  minute  changes  of  tempera- 
ture, which  the  mercurial  thermometer  would  scarcely  discover ; for 
air  is  increased  in  volume  by  a given  elevation  of  temperature,  about 
twenty  times  more  than  quicksilver.  The  advantages,  however, 
which  attend  this  excessive  delicacy  are  counterbalanced  by  sever- 
al serious  objections.  It  will  be  readily  seen,  for  instance,  that  the 
air  thermometer  will  not  only  be  affected  by  changes  of  temperature, 
but  by  variations  of  atmospheric  pressure. 

166.  Leslie,  under  the  name  of  the  Differential  Ther- 
mometer, employed  a modification  of  the  air  thermome- 
ter invented  by  Sturmius.*  It  consists  of  two  glass- 
tubes  of  unequal  length,  each  terminating  in  a hollow 
ball,  as  represented  in  Fig.  31,  which  are  united  by  a 
bent  tube  containing  coloured  sulphuric  acid.  When- 
ever a hot  body  approaches  one  of  the  bulbs,  it  must  ne- 
essarily  drive  the  fluid  towards  the  other.  It  is  evident 
then  that  this  instrument  cannot  be  employed  to  measure 
variations  in  the  temperature  of  the  surrounding  atmos- 
phere, because,  as  long  as  both  balls  are  of  the  same  temperature, 
whatever  this  may  be,  the  air  contained  in  both  will  have  the  same 
elasticity,  and  consequently,  the  included  coloured  liquor,  being 
pressed  equally  in  opposite  directions,  must  remain  stationa- 
ry. If,  however,  any  change  of  temperature  is  effected 
in  one  of  the  balls,  the  instrument  will  immediately  indi- 
cate this  difference  with  the  greatest  nicety.  The  amount 
of  this  effect  is  ascertained  by  a graduated  scale,  the  in- 
terval between  freezing  and  boiling  being  divided  into 
100  equal  degrees.  This  thermometer  is  peculiarly 
adapted  to  ascertain  the  difference  of  the  temperatures  of 
two  contiguous  spots  in  the  same  atmosphere. 

A differential  thermometer  has  been  contrived  by  How- 
ard resembling  the  above  in  its  general  form,  (Fig.  32)  but  in 


Fig.  31. 


Fig.  3 2. 

1 


o 


SJ 


* See  a description  and  sketch  in  his  Collegium  Curiosum,  p.  54  ; published  in  1676. 


Thermometer. 


47 


which  the  degree  of  heat  is  measured  by  the  expansive  force  of  Sect,  hi. 
the  vapour  of  ether,  or  spirit  of  wine,  in  vacuo.*"  It  is  intended 
to  be  applied,  to  the  same  purposes  as  that  of  Leslie,  but  is  more 
sensible  to  changes  of  temperature,  and  the  movement  of  the 
fluid  follows  instantaneously  the  application  of  the  heating  cause, 
whereas  in  the  air  thermometer  some  time  is  required  before  the 
effect  takes  place. 

167.  Different  methods  have  been  recommended  for  ascertaining  Self-regis- 
the  highest  or  lowest  temperature  that  may  occur  during  any  parti-  teving  ther-* 
cular  period,  as  during  the  night,  when  there  is  no  one  present  to  ob-  mome 
serve  it.  The  simplest  contrivance  of  this  kind  is  the  following : 


It  consists  of  two  thermometers  (Fig.  33),  a Sp^t  0f  wine  and  a mercurial  one 
the  former  for  ascertaining  the  lowest,  the 

latter  the  highest  heat.  In  the  tube  of  the  Fig.  33- 

former  is  placed  a small  piece  of  white  ena-  &) 

mel,  which,  as  the  fluid  contracts,  is  brought 
along  with  it,  but  on  its  again  expanding  does 
not  take  it  with  it ; it  leaves  it  at  the  place  to 
which  it  had  carried  it,  and  thus  the  lowest 
temperature  that  had  happened  is  pointed 
out.  In  the  tube  of  the  latter  is  placed  a small  piece  of  a needle,  so  as  just  to 
rest  on  the  mercury.  As  the  fluid  expands,  it  pushes  the  needle  before  it  and 
on  again  contracting,  it  leaves  it  at  that  part  to  which  it  had  carried  it,  so  that 
in  this  way  the  highest  temperature  is  ascertained;  These  thermometers  are 
fixed  on  a board,  with  the  balls  at  opposite  sides,  the  mercurial  one  horizontally, 
the  one  with  spirit  of  wine  with  the  ball  inclined  downwards,  so  that,  when  we  wish 
to  set  them,  by  raising  the  side  next  the  spirit  ball,  the  enamel  and  needle  will 
come  to  the  surfaces  of  the  fluids. 

Six’s  thermometer  (Fig.  34),  has  the  bulb  in  the  form  of  a long  cylin-  Fig.  34. 
der,  the  tube  is  bent  down  parallel  with  the  cylinder  and  passing  under  Jsi^ 
it,  rises  in  a parallel  direction  to  the  top  on  the  other  side  ; the  bulb  is 
usually  filled  with  spirits  of  wine,  which  is  in  contact  with  a portion  of 
mercury  occupying  the  lower  part  of  the  tube,  and  the  mercury  is  suc- 
ceeded by  a second  portion  of  spirit.  The  mercury  carries  an  index 
upon  each  of  its  surfaces;  when  the  fluid  in  the  cylinder  contracts  by 
cold,  the  index  on  the  left  side  will  be  pressed  upwards,  as  long  as  the 
heat  decreases,  and  will  be  retained  at  its  greatest  height  by  a weak 
spring.  When  the  fluid  in  the  cylinder  expands  by  heat,  it  must  press 
upon  the  surface  of  the  mercury  in  the  left  side  of  the  tube,  forcing  it 
to  rise  higher  in  the  right  side  : as  long  as  the  heat  continues  to  increase, 
the  index  will  rise  on  the  surface  of  the  mercury  in  the  right  side  of  the 
tube,  and  will  be  retained  at  the  greatest  height  by  its  spring  : it  must  be 
obvious,  therefore,  that  the  index  on  the  side  opposite  the  left  hand  will 
indicate  the  greatest  degree  of  cold,  in  any  given  time,  and  the  one  on 
the  right,  the  greatest  degree  of  heat.  The  indexes  being  of  iron  or  steel, 
may  be  brought  back  to  their  places  by  a magnet,  applied  to  the  outside  of 
the  tube. 


168.  Though  the  thermometer  is  a most  valuable  instrument,  the  Amount  of 
sum  of  information  which  it  conveys  is  very  small.  It  only  indicates 
that  condition  of  bodies  in  which  they  affect  the  senses  with  an  im-  mometer 
pression  of  heat  or  cold,  and  which  is  expressed  by  the  word  temper- 
ature. It  does  indeed  point  out  a difference  in  the  temperature  of 
two  or  more  substances  with  great  nicety  ; but  it  does  not  indicate 
how  much  heat  any  body  contains.  We  learn  by  it  whether  the 
temperature  of  one  body  is  greater  or  less  than  that  of  another ; and 
if  there  is  a difference,  it  is  expressed  numerically,  namely,  by  the 
degrees  of  an  arbitrary  scale,  selected  for  convenience,  without  any 
reference  whatever  to  the  actual'  quantity  of  heat  present  in  bodies. 


* Directions  for  constructing  it  are  given  in  the  8th  vol.  of  the  Quart.  Jour,  of  Sci. 
p,  219. 


48 


Caloric. 


Chap.  I. 

Specific  ca 
loric. 


Exp. 


Exp. 


Different 
quantities 
of  heat  re 
quired  by 
bodies. 


169.  The  relative  quantities  of  heat  which  different  bodies  in  the 
. same  state  require  to  raise  them  to  the  same  thermoinetric  tempera- 
ture, is  called  their  specific  heat,  and  those  bodies  which  require 
most  heat  are  said  to  have  the  greatest  capacity  for  heat.  That  the 
quantity  of  heat  in  different  bodies  of  the  same  temperature  is  dif- 
ferent, was  first  shown  by  Black,  in  1762. 

Mix  together  equal  quantities  of  water,  one  portion  being  at  100°  and  the  other 
at  50°,  the  temperature  of  the  mixture  will  be  the  arithmetical  mean  or  75° ; 
that  is,  the  25  degrees  lost  by  the  warm  water  will  exactly  suffice  to  heat  the  cold 
water  by  the  same  number  of  degrees. 

It  is  hence  inferred,  that  equal  weights  or  measures  of  water  of 
the  same  temperature  contain  equal  quantities  of  heat;  and  the  same 
is  found  to  be  true  of  other  bodies.  But  if  equal  weights  or  equal 
bulks  of  different  substances  are  employed,  the  result  will  be  different. 

Thus,  if  a pint  of  mercury  at  100°  be  mixed  with  a pint  of  water  at  40Q,  the 
mixture  will  nave  a temperature  of  60°,  so  that  the  4U  degrees  lost  by  the  for- 
mer, heated  the  latter  by  20  degrees  only  ; and  when,  reversing  the  experiment, 
the  water  is  at  100°  and  the  mercury  at  40°,  the  mixture  will  be  at  80°,  the  20 
degrees  lost  by  the  former  causing  a rise  of  40  in  the  latter. 

The  fact  is  still  more  strikingly  displayed  by  substituting  equal 
weights  for  measures. 

170.  k appears  that  the  same  quantity  of  heat  imparts  twice  as 
high  a temperature  to  mercury  as  to  an  equal  volume  of  water  ; a 
similar  proportion  is  observed  with  respect  to  equal  weights  of  sper- 
maceti oil  and  water;  and  that  the  heat  which  gives  5 degrees  to 
water  will  raise  an  equal  weight  of  mercury  by  115  degrees,  being 
the  ratio  of  1 to  23.  Hence  if  equal  quantities  of  heat  be  added  to 
equal  weights  of  water,  spermaceti  oil,  and  mercury,  their  tempera- 
tures in  relation  to  each  other  will  be  expressed  by  the  numbers  1,2, 
and  23 ; or,  what  amounts  to  the  same,  in  order  to  increase  the  tem- 
perature of  equal  weights  of  those  substances  to  the  same  extent,  the 
water  will  require  23  times  as  much  heat  as  the  mercury,  and  twice 
as  much  as  the  oil.  T.  29. 

This  may  be  illustrated  by  an  inge- 
nious apparatus  contrived  by  Bache. 

Three  vessels  of  sheet  iron,  (Fig.  35)  to 
contain  equal  iceights  of  mercury,  alco- 
hol, and  water,  are  attached  to  a frame, 
by  which  they  can  be  dipped  intothesame 
vessel  containing  hot  water.  An  alcohol 
thermometer,  with  a large  column  of  fluid,  dips  into  each  vessel.  As 
the  heat  enters,  the  thermometer  in  the  mercury  rises  with  great  ra- 
pidity, that  in  the  alcohol  more  slowly,  and  that  in  the  water  still 
more  so.* 

171.  The  same  knowledge  may  be  obtained  by  reversing  the  pro- 
cess ; by  noting  the  relative  quantities  of  caloric  which  bodies  give 
out  in  cooling  ; for  if  water  requires  23  times  more  caloric  than  mer- 
cury to  raise  its  temperature  1 or  more  degrees,  it  must  also  lose  23 
times  as  much  in  cooling.  The  calorimeter , invented  and  employed 
by  Lavoisier  and  La  Place,  acts  on  this  principle.! 


Fig.  35. 


* Cylinders  of  copper,  coaled  with  a varnish  of  thickened  linseed  oil  to  protect  the 
surface,  may  be  substituted  for  the  thermometers,  phosphorus,  placed  on  the  top  of 
each,  will  inflame  first  ou  the  cylinder  in  the  liquid  having  the  least  capacity  for  heat. 
Amer.  Jour,  xxviii.  324.  + See  Lavoisier’s  Elements  of  Chemistry. 


Specific  Caloric.  49 

172.  The  singular  fact  of  substances  of  equal  temperature,  con-  Sect,  nr. 
taining  unequal  quantities  of  heat,  naturally  excites  speculation  about  Cause, 
its  cause,  and  various  attempts  have  been  made  to  account  for  it. 

The  explanation  deduced  from  the  views  of  Black  is  the  following. 

He  conceived  that  heat  exists  in  bodies  in  two  opposite  states  : in 
one  it  is  supposed  to  be  in  chemical  combination,  exhibiting  none  of 
its  ordinary  characters,  and  remaining  as  it  were  concealed,  without 
evincing  any  signs  of  its  presence;  in  the  other,  it  is  free  and  un- 
combined, passing  readily  from  one  substance  to  another,  affecting 
the  senses  in  its  passage,  determining  the  height  of  the  thermometer, 
and  in  a word  giving  rise  to  all  the  phenomena  which  are  attributed 
to  this  active  principle.* 

373.  The  capacities  of  bodies  for  heat  have  considerable  influence  Heating 
upon  the  rate  at  which  they  are  heated  and  cooled.  Those  bodies  which  and  cooling 
are  most  slowly  heated  and  cooled,  have  generally  the  greatest  caPa' -^fluenml 
city  for  heat.  Thus*  if  equal  quantities  of  water  and  quicksilver  be  by  capac- 
placed  at  equal  distances  from' the  fire,  the  quicksilver  will  be  more  by- 
rapidly  heated  than  the  water,  and  the  metal  will  cool  most  rapidly 
when  carried  to  a cold  place.  Upon  this  principle,  Leslie  ingeniously  Tes]je>s 
determined  the  specific  heat  of  bodies,  observing  their  relative  times  method, 
of  cooling  a certain  number  of  degrees  comparatively  -with  water, 
under  similar  circumstances. 

174.  The  determination  of  the  specific  heat  of  gaseous  substances  Specific 
is  a problem  of  importance,  and  has  accordingly  occupied  the  atten-  heat  of 
tion  of  several  experimenters  of  great  science  and  practical  skill  ; §ase8‘ 
but  the  inquiry  is  beset  with  so  many  difficulties  that,  in  spite  of  the 
talent  which  has  been  devoted  to  it,  our  best  results  can  be  viewed  as 
approximations  only,  requiringfo  be  corrected  by  future  research. f 

175.  The  circumstances  which  merit  particular  notice,  concerning  Circum- 

the  specific  heat  of  bodies,  have  been  arranged  by  Turner  under  the  stances  lo 
eight  following  heads  " be  noticed. 

1.  Every  substance  has  a specific  heat  peculiar  to  itself  ; whence 
it  follows,  that  a change  of  composition  will  be  attended  by  a change 
of  capacity  for  heat. 

2.  The  specific  heat  of  a body  varies  with  its  form.  A solid  has 
a smaller  capacity  for  heat  than  the,  same  substance  when  in  the  state 
of  a liquid. 

3.  When  a given  weight  of  any  gas  is  made  to  vary  in  density 
and  volume  while  its  elasticity  is  unchanged,  as  when  air  confined  in 
a tube  over  mercury  is  heated  and  suffered  to  expand  without  varia- 
tion of  pressure,  the  specific  heat  is  believed  to  remain  constant. 

4.  Of  the  specific  heat  of  equal  volumes  of  the  same  gas  at  a vary- 
ing density  and  elasticity,  as  when  air  is  forced  into  a bottle  with 
different  degrees  of  force,,  nothing  certain  has  been  established. 

5.  The  specific  heat  of  equal  weights  of  the  same  gas  varies  as 
the  density  and  elasticity  vary. 

6.  The  specific  heat  of  solids  and  liquids  was  formerly  thought  to 
be  constant  at  all  temperatures,  so  long  as  they  suffer  no  change  of 
form  or  composition.  Dalton,  however,  {Chemical  Philosophy,  part 


* For  objections  to  this  theory,  see  note  by  Bache,  p.  30,  Turner’s  Elements,  Am.  ed. 
t For  a view  of  the  experiments  of  Crawford,  Lavoisier,  Dulong,  and  others,  on  this 
subject,  see  Turner's  Elements , p.  31. 

7 


50 


Caloric. 


Chap.  I. 


Dilatation 
of  air,  &c. 


Exp. 


I.  p.  50,)  endeavours  to  show  that  the  specific  heat  of  such  bodies  is 
greater  in  high  than  at  low  temperatures  ; and  Petit  and  Dulong 
have  proved  it  experimentally  with  respect  to  several  of  them. 

It  is  difficult  to  determine  whether  the  increased  specific  heat  ob- 
served in  solids  and  liquids  at  high  temperatures  is  owing  to  the  ac- 
cumulation of  heat  within  them,  or  to  their  dilatation.  It  is  ascribed 
in  general  to  the  latter. 

176.  Change  of  specific  heat  always  occasions  a change  of  tem- 
perature. Increase  in  the  former  is  attended  by  diminution  of  the 
latter ; and  decrease  in  the  former  by  increase  of  the  latter. 


Thus  when  air,  confined  within  a flaccid  bladder,  is  suddenly  dilated  by 
means  of  the  air-pump,  a thermometer  placed  in  it  will- indicate  the  pro- 
duction of  cold.  On  the  contrary,  wnen  air  is  compressed,  the  corres- 
ponding diminution  of  its  specific  heat  gives  rise  to  increase  of  tempera- 
; nay,  so  much  heat  is  evolved  when  the  compression  is  sudden  and 
ible,  that  tinder  may  be  kindled  by  it.  This  is  illustrated  by  a brass 


Fig.  36. 


ture  ; 
fore 


syringe  furnished  at  one  end  with  a stop  cock  having  a small  cham- 
ber in  which  tinder,  or  what  is  better,  a small  piece  of  phosphorus 
wrapped  in  tow,  is  placed.  By  suddenly  compressing  the  piston,  the 
tinder  takes  fire  on  opening  the  stop  cock.  Or  the  tinder  may  be  placed 
in  a cavity,  in  the  end  of  the  piston. 

The  explanation  of  these  facts  is  obvious.  In  the  first  case, 
a quantity  of  heat  becomes  insensible,  which  was  previously  in 
a sensible  state;  in  the  second,  heat  is  evolved,  which  was  pre- 
viously latent.  -U 

Relation  of  A curious  relation  between  the  specific  heat  of  some  ele-  D® 
heat^and  raenlary  substances  and  their  atomic  weight  was  discovered  by  Du- 
weight.  long  and  Petit ; namely,  that  the  product  of  the  specific  heat  of  each 
element  by  the  weight  of  its  atom  is  a constant  quantity. 

Forma  and  177.  Heat  has  great  influence  on  the  forms  or  states  of  bodies, 
states  of  When  we  heat  a solid  it  becomes  fluid  or  gaseous,  and  liquids  are 
fl^iKetTby  converle(^  int0  aeriform  bodies  or  vapours.  Black  investigated  this 
caloric.  effect  of  heat  with  singular  felicity.*  During  the  liquefaction  of 
bodies,  a quantity  of  heat,  which  is  essential  to  the  state  of  fluidity, 
and  which  is  therefore  often  called  the  heat  of  fluidity , is  absorbed, 
without  increasing  the  sensible  or  thermoinetric  temperature.  Con- 
sequently, if  a cold  solid  body,  and  the  same  body  hot  and  in  a 
liquid  state,  be  mixed  in  known  proportions,  the  temperature  after  mix- 
ture will  not  be  the  proportional  mean,  as  would  be  the  case  if  both 
were  liquid,  but  will  fall  short  of  it ; much  of  the  heat  of  the  hotter 
body  being  consumed  in  rendering  the  colder  solid  liquid , before  it 
produces  any  effect  upon  its  sensible  temperature. 

178.  Equal  parts  of  water  at  32°,  and  of  water  at  212°,  will  pro- 
duce on  mixture  a mean  temperature  of  122°.  But  equal  parts  of 
ice  at  32°,  and  of  water  at  212°,  will  only  produce  (after  the  lique- 
faction of  the  ice)  a temperature  of  52°,  the  greater  portion  of  the  heat 
of  the  water  being  employed  in  thawing  the  ice,  before  it  can  produce 
any  rise  of  temperature  in  the  mixture.  To  heat  thus  insensible  or 
bric0t  Ca  combined.  Black  applied  the  term  latent  heat.  The  actual  loss  of 
the  thermometric  heat  in  these  cases  was  thus  estimated  ; a pound 
of  ice  at  32°  was  put  into  a pound  of  water  at  172° , the  ice  melted, 
and  the  temperature  of  the  mixture  was  32°.  Here  the  water  was 


* Black’s  Lectures. 


Freezing  Mixtures . 51 

cooled  140°,  while  the  temperature  of  the  ice  was  unaltered  ; that  is,  .Sect,  m. 
140°  of  heat  disappeared,  their  effect  being  not  to  increase  tempera- 
ture, but  to  produce  fluidity. 

179.  In  all  cases  of  liquefaction  caloric  is  absorbed,  and  we  pro-  Cold  pro- 
duce artificial  cold,  often  of  great  intensity,  by  the  rapid  solution  ^JaTdsofu 
certain  saline  bodies  in  water.^  Upon  this  principle  the  action  of  80 
freezing  mixtures  depends,  some  of  which  may  frequently  be  conve- 
niently and  economically  applied  to  the  purpose  of  cooling  wine  or 
water  in  hot  climates,  or  where  ice  cannot  be  procured. 

Dilute  a portion  of  nitric  acid  with  an  equal  weight  of  water ; and,  when  the  Exp.  1 . 
mixture  has  cooled,  add  to  it  a quantity  of  light  fresh-fallen  snow.  On  immers- 
ing the  thermometer  in  the  mixture,  a very  considerable  reduction  of  tempera- 
ture will  be  observed.  This  is  owing  to  the  absorption,  and  intimate  fixation  of 
the  free  caloric  of  the  mixture  by  the  liquefying  snow. 

Mix  quickly  together  equal  weights  of  fresh-fallen  snow  at  32°,  and  of  com-  Exp.  2. 
mon  salt,  cooled,  by  exposure  to  a freezing  atmosphere,  down  to  32°.  The  two 
solid  bodies,  on  admixture,  will  rapidly  liquefy,  and  the  thermometer  will  sink 
32°  or  to  0°,  or  according  to  Blagden  to  4+  lower. 

To  understand  this  experiment,  it  must  be  recollected,  that  the  snow  Theory, 
and  salt,  though  at  the  freezing  temperature  of  water,  have  each  a 


*FRIGORIFIC  MIXTURES  WITH  SNOW* 


Mixtures. 

Parts 
hy  weight. 

Sea-salt,  ...  1 

Snow,  . ...  2 

from  any  temperature 

rhermometer  sinks 
to  —5° 

Degree  of  Cold  pro- 
duced. 

Sea-salt,  ...  2 

Hydrochlorate  of  ammonia,  1 
Snow,  ....  5 

0 

u 

to 

0 

Sea-salt,  . . . .10 

Hydrochlorate  of  ammonia,  5 
Nitrate  of  potassa,  . . 5 

Snow,  ....  24 

0 

1 

CO 

0 

Sea-salt,  . ...  5 

Nitrate  of  ammonia,  . 5 

Snow,  . . . .12 

to  —25° 

Diluted  sulphuric  acid,t  2 

Snow,  . . - .3 

from  +32°  to  —23° 

55  degrees. 

Concentrated  hydrochloric  j g 
Snow,  . . , .8 

from  4-32°  to  —27° 

59 

Concentrated  nitrous  acid,  4 
: Snow,  . . . 7 

from  +32°  to  —30° 

62 

Chloride  of  calcium,  . 5 

Snow,  ....  4 

from  4-32°  to  —40° 

72 

Crystallized  chloride  of?  3 
calcium,  <> 

Snow,  ....  2 

from  4-32°  to  —50° 

82 

Fused  potassa,  . , 4 

; Snow,  . ...  3 

front  4-32°  to  —51° 

83 

But  freezing  mixtures  may  be  made  by  the  rapid  solution  of  salts,  without  the  use 
of  snow  or  ice;  and  the  following  table,  taken  from  Walker’s  Essay  in  thePhilosoph- 

+ Phil.  Trans.  Ixxviii.  281. 

*The  snow  should  be  freshly  fallen,  dry.  and  uncompressed.  If  snow  cannot  be  had,  finely 
powdered  ice  mpy  be  substituted  for  it. 
f Made  of  strong  acid,  diluted  with  half  its  weight  of  snow  or  distilled  water. 


52 


Caloric. 


Chap,  i.  considerable  portion  of  uncombined  caloric.  Now  salt  has  a strong 
affinity  for  water ; but  the  union  cannot  take  place  while  the  water 
continues  solid.  In  order,  therefore,  to  act  on  the  salt,  the  snow  ab- 
sorbs all  the  free  caloric  required  for  its  liquefaction  ; and  during 
this  change,  the  free  caloric,  both  of  the  snow  and  the  salt,  amount- 
ing to  32°,  becomes  latent,  and  is  concealed  in  the  solution.  This 
solution  remains  in  a liquid  state  at  0,  or  4°  below  0 of  F. ; but  if  a 
greater  degree  of  cold  be  applied  to  it,  the  salt  separates  in  a con- 
crete form. 

Most  neutral  salts,  also,  during  solution  in  water,  absorb  much  ca- 
loric ; and  the  cold,  thus  generated,  is  sometimes  so  intense  as  to 
freeze  water,  and  even  to  congeal  mercury.  The  former  experiment, 
however,  (viz.  the  congelation  of  water,)  may  easily  be  repeated  on 
a summer’s  day. 

Exp.  Add  to  32  drachms  of  water,  11  drachms  of  hydrochlorate  of  ammonia,  10  of 

nitrate  of  potassa,  and  16  of  sulphate  of  soda,  all  finely  powdered.  The  salts  may 


icul  Transactions  for  1795,  includes  the  most  important  of  them.  The  salts  must  be 
finely  powdered  aud  dry. 


Mixtures. 

Parts 
by  weight- 

Hydrochlorate  of  ammonia.  5 
Nitrate  of  potassa,  5 

Water 16 

Temperature  falls 
from  +50°  to  +10° 

Degree  of  Cold  pro- 
duced. 

40  degrees. 

Hydrochlorate  of  ammonia,  5 
Nitrate  of  potassa,  . . 5 

Sulphate  of  soda,  . 8 

Water,  . . 16 

from  +50°  to  +4° 

46 

Nitrate  of  ammonia,  1 

Water 1 

from  +50°  to  4-4° 

46 

Nitrate  of  ammonia,  1 

Carbonate  of  soda,  . . 1 

Water,  ....  1 

from  4-50°  to  —7° 

57 

Sulphate  of  soda,  . 3 

Diluted  nitrous  acid,*  2 

from  4-50°  to  —3° 

53 

Sulphate  of  soda,  6 

Hydrochlorale  of  ammonia,  4 
Nitrate  of  potassa,  . 2 

Diluted  nitrous  acid.  4 

from  4-50°  to  — 10° 

60 

Sulphate  of  soda,  . • 6 

Nitrate  of  ammonia,  5 

Diluted  nitrous  acid,  4 

from  4-50°  to  — 14° 

64 

Phosphate  of  soda.  . 9 

k >iluted  nitrous  acid,  . 4 

from  4-50°  to  — 12° 

62 

Phosphate  of  soda.  . 9 

Nitrate  of  ammonia.  . 6 

Diluted  nitrous  acid.  4 

from  4-50°  to  —21° 

71 

Sulphate  of  soda.  . 8 

Hydrochloric  acid,  5 

from  +50°  to  0° 

50 

1 Sulphate  of  soda,  . 6 

1 Diluted  sulphuric  acid.t  4 

from  4-50°  to  4-3° 

47 

These  artificial  processes  for  generating  cold  are  mnch  more  effectual  when  the  ma- 
terials are  previously  cooled  by  immersion  in  other  frigorific  mixtures. 


* Composed  of  fuming  nitrous  acid  two  parts  in  weight,  and  one  of  water — the  mixture  being 
allowed  to  cool  before  being  used. 

f Composed  of  equal  weights  of  strong  acid  and  water,  being  allowed  to  cool  before  use. 


Latent  and  Sensible  Heat.  53 

be  dissolved  separately,  in  the  order  set  down,  A thermometer,  put  into  the  Sect.  III. 
solution,  will  show,  that  the  cold  produced  is  at,  or  below  freezing;  and  a little  T ° 
water,  in  a thin  glass  tube,  being  immersed  in  the  solution,  will  be  frozen  in  **■ 
a few  minutes.  H.  1.  113,* 

Crystallized  chloride  of  calcium,  when  mixed  with  snow,  pro- Method  of 
duces  a most  intense  degree  of  cold.  This  property  was  discovered  J^cury 
by  Lovitz,  and  has  bpen  since  applied  to  the  congelation  of  mercury 
on  a very  extensive  scale.! 

On  a small  scale,  it  may  be  sufficient  to  employ  two  or  three 
pounds  of  the  salt, 

Let  a few  ounces  of  mercury,  in  a very  thin  glass  retort,  be  immersed,  first  Exp. 
in  a mixture  of  one  pound  of  each  ; and,  when  this  has  ceased  to  act,  let  another 
similar  mixture  be  prepared.  The  second  will  never  fail  to  congeal  the  quick- 
silver.t 

180.  When  fluids  are  converted  into  solids,  their  latent  heat  be- Latent  ca- 
comes  sensible.  Water,  if  kept  perfectly  free  from  agitation,  may  bej^™.®^® 
cooled  down,  several  degrees  below  32°  ; but,  on  shaking  it,  it  imme- 
diately congeals,  and  the  temperature  rises  to  32°. 

The  evolution  of  caloric,  during  the  congelation  of  water  is  well 
illustrated  by  the  following  experiment  of  Crawford. 

Into  a round  tin  vessel  put  a pound  of  powdered  ice;  surround  this  by  ag  l 
mixture  of  snow  and  salt  in  a larger  vessel ; and  stir  the  ice  in  the  inner  one,  till 
its  temperature  is  reduced  to  + 4°  F.  To  the  ice  thus  cooled  add  a pound  of 
water  at  32°.  One  fifth  of  this  will  be  frozen  ; and  the  temperature  of  the  ice 
will  rise  from  4°  to  32°.  In  this  instance,  the  caloric  evolved,  by  the  congela- 
tion of  one  fifth  of  a pound  of  water,  raises  the  temperature  of  a pound  of  ice 
28°.  H.  1.  115. 

Dissolve  sulphate  of  soda  in  water,  in  the  proportion  of  one  part  to  five,  and  „ 
surround  the  solution  by  a freezing  mixture,  it  will  cool  gradually  down  to  31°.  ' 

The  salt,  at  this  point,  begins  to  be  deposited,  and  stops  the  cooling  entirely. 


* The  results  of  some  of  Walker’s  experiments  on  this  subject,  are  given  in  the  ta- 
bles of  freezing  mixtures. 

t The  proportions,  which  answer  best,  are  about  equal  weights  of  the  salt  finely 
powdered,  and  of  fresh  fallen  and  light  snow.  On  mixing  these  together,  and  im- 
mersing a thermometer  in  the  mixture,  the  mercury  sinks  with  great  rapidity.  For 
measuring  exactly  the  cold  produced,  a spirit  thermometer,  graduated  to  50°  below  0 
of  Fahrenheit,  or  still  lower  should  be  employed.  A few  pounds  of  the  salt  are  suf- 
ficient to  congeal  a large  mass  of  mercury.  By  means  of  13  pounds  of  the  chloride, 
and  an  equal  weight  of  snow,  Pepys  and  Allen  froze  56  pounds  of  quicksilver  into  a 
solid  mass.  The  mixture  of  the  whole  quantity  of  salt  and  snow,  however,  was  not 
made  at  once,  but  part  was  expended  in  cooling  the  materials  themselves. 

t Fig.  37,  a very  simple  and  cheap  apparatus  may  be  employed  to  freeze  mercury. 
The  outer  vessel  of  wood  may  be  twelve  and  a half  inches  square,  and  seven  inches 
deep.  It  should  have  a wooden  cover,  rabbeted  in,  and  furnished  with  a handle. 
Within  this  is  placed  a tin  vessel  b b,  standing  on  feet  which  are  one  and  a half  inches 
high,  and  having  a projection  at  the  top,  half  an  inch  Fig.  37. 

broad  and  an  inch  deep,  on  which  rests  a shallow  tin  pan 
c c.  Within  the  second  vessel  is  a third  d,  made  of  un- 
tinned iron,  and  supported  by  feet  two  inches  high. 

This  vessel  is  four  inches  square,  and  is  intended  to  con- 
tain the  mercury.  When  the  apparatus  is  used,  a mix- 
ture of  hydrocnlorate  of  lime  and  snow  is  put  into  the 
outer  vessel  a a,  so  as  completely  to  surround  the  middle  a 
vessel  b b.  Into  the  latter,  the  vessel  d,  containing  the  quicksilver  to  be  frozen,  pre- 
viously cooled  down  by  a freezing  mixture,  is  put ; and  this  is  immediately  surroun- 
ded by  a mixture  of  snow  and  muriate  of  lime,  previously  cooled  to  0°  F.  by  an 
artificial  mixture  of  snow  and  common  salt.  The  pan  c c is  also  filled  with  these 
materials,  and  the  wooden  cover  is  then  put  into  its  place.  The  vessels  are  now  left 
till  the  quicksilver  is  frozen.  A more  elegant,  but  more  expensive,  apparatus,  by 
Pepys,  intended  for  the  same  purpose,  is  figured  in  an  early  volume  of  the  Philosophi- 
cal Magazine.  H.  1.  114. 


54 


Caloric. 


Chap,  i.  This  evolution  of  calorie  during  the  separation  of  a salt,  is  exactly 
the  reverse  of  what  happens  during  its  solution.* 

When  a solution  of  Glauber’s  salt  is  made  suddenly  to  crystal- 
lize, its  temperature  is  considerably  augmented  ; (31  note)  and  when 
^ water  is  poured  upon  quicklime,  a great  degree  of  heat  is  produced 
by  the  solidification  which  it  suffers  in  consequence  of  chemical 
combination  ; congelation,  therefore,  is  to  surrounding  bodies  a 
heating  process,  and  liquefaction  a cooling  process. 
of7Vuid°n  liquid*  are  heated  they  acquire  the  gaseous  form,  and 

into ‘the  * become  invisible  elastic  fluids,  possessed  of  the  mechanical  proper- 
aeriform  ties  of  common  air.  By  a sufficiently  intense  heat  every  liquid  and 
state.  solid  would  probably  undergo  this  change.  A considerable  number  of 
bodies,  however,  resist  the  strongest  heat  of  our  furnaces  without  va- 
porizing. These  are  said  to  be  fixed  in  the  fire : those  which,  under 
the  same  circumstances,  are  converted  into  vapour,  are  called  volatile . 
This  effect  of  caloric  is  termed  Vaporization. 

Vapours  182.  Vapours  are  characterized  by  the  readiness  with  which  they 
are  convertible  into  liquids  or  solids,  either  by  a moderate  increase 
of  pressure,  the  temperature  at  which  they  were  formed  remaining 
the  same,  or  by  a moderate  diminution  of  that  temperature,  without 
change  of  pressure.  They  retain  this  form  or  state  as  long  as  their 
temperature  remains  sufficiently  high,  but  re-assume  the  liquid  form 
when  cooled  again. 


Exp.  i. 


Exp.  2. 


Fill  a jar  with  water  heated  to  101°  and  invert  it  in  a vessel  of  the  same.  Then 
introduce  a little  ether  by  means  of  a glass  tube  closed  at  one  end.  The  ether 
will  rise  to  the  top  of  the  jar,  and,  in  its  ascent  will  be  changed  into  gas,  filling 
the  whole  jar  with  a transparent,  invisible,  elastic  fluid.  On  permitting  the 
water  to  cool,  the  etiiereal  gas  is  condensed,  and  the  inverted  jar  again  becomes 
filled  with  water. 

Or  more  beautifully  thus.  Fill  a glass  tube  about  thirty  inches  long  and 
an  inchin  diameter,  with  quicksilver,  and  invert  it  in  the  mercurial  trough.  Pass 
up  from  a small  bottle  an  ounce  or  more  of  ether ; after  it  has  collected  upon  the 
surface  of  the  quicksilver  in  the  tube,  it  may  be  made  to  boil  by  the  heat  of  the 
hand  by  grasping  the  tube  at  that  part  where  the  ether  stands;  which  will  pass 
to  the  state  of  vapour  and  depress  the  mercurial  column. 


Difference  1S3.  The  disposition  of  various  substances  to  yield  vapour  is  very 
of  density,  different ; and  the  difference  depends  doubtless  on  the  relative  pow- 
er of  cohesion  with  which  they  are  endowed.  Vapours  occupy 
more  space  than  the  substances  from  which  they  were  produced. 
According  to  the  experiments  of  Gay  Lussac,  water,  at  its  point  of 
greatest  density,  in  passing  into  vapour,  expands  to  1696  times  its 
volume,  alcohol  to  659  times,  and  ether  to  443  times,  each  vapour  be- 
ing at  a temperature  of  212°  F.  and  under  a pressure  of  29.92  inches 
of  mercury.  This  shows  that  vapours  differ  in  density.  Watery 
vapour  is  lighter  than  air  at  the  same  temperature  and  pressure,  in 
the  proportion  of  1000  to  1604  ; or  the  density  of  air  being  1000, 
that  of  watery  vapour  is  625.  The  vapour  of  alcohol,  on  the  contra- 
ry, is  half  as  heavy  again  as  air ; and  that  of  ether  is  more  than 
twice  and  a half  as  heavy. 

Dilatation  184.  The  dilatation  of  vapours  by  heat  was  found  by  Gay-Lus- 
of  vapours.  sac  to  follow  the  same  law  as  gases,  that  is,  for  every  degree  of 
Fahrenheit,  they  increase  by  y^th  of  the  volume  they  occupied  at 
32°.  But  the  law  does  not  hold  unless  the  quantity  of  vapour  con- 


Blagden,  Phil.  Trans.  Ixxviii.  290. 


55 


Boiling  Point. 


Sect.  III. 


tinue  the  same.  If  the  increase  of  temperature  cause  a fresh  por- 

tion  of  vapour  to  rise,  then  the  expansion  will  be  greater  than  ^-gth 
for  each  degree  ; because  the  heat  not  only  dilates  the  vapour  pre- 
viously existing  to  the  same  extent  as  if  it  were  a real  gas,  but  aug- 
ments its  bulk  by  adding  a fresh  quantity  of  vapour.  The  contrac- 
tion of  a vapour  on  cooling  will  likewise  deviate  from  the  above  law, 
whenever  the  cold  converts  any  of  it  into  a liquid  ; an  effect  which 
must  happen,  if  the  space  had  originally  contained  its  maximum  of 
vapour; 

The  volume  of  vapour  varies  under  varying  pressure  according  to  Influenced 
the  same  law  as  that  of  gases,  provided  always  that  the  gaseous  gur^es’ 
state  is  preserved.  This  law,  discovered  by  Boyle  and  Mariotte,  is 
more  fully  explained  in  the  section  on  atmospheric  air,  and  merely 
expresses  the  fact  that  the  volume  of  gaseous  substances  at  a constant 
temperature  is  inversely  as  the  pressure  to  which  they  are  subject. 

155.  The  temperature  at  which  vapour  rises  with  sufficient  free- Boiling 
dom  for  causing  the  phenomena  of  ebullition,  is  called  the  boiling  point  of 
point.  The  heat  requisite  for  this  effect  varies  with  the  nature  of  jiflulds 
the  fluid.  Thus,  sulphuric  ether  boils  at  96°  F.  alcohol  at  173°  and 
pure  water  at  212°  ; while  oil  of  turpentine  must  be  raised  to  316°, 
and  mercury  to  662°,  before  either  exhibits  marks  of  ebullition.  The 
appearance  of  boiling  is  owing  to  the  formation  of  vapour  at  the  bot- 
tom of  the  Vessel,  and  it  escapes  through  the  heated  fluid  above  it. 

186.  The  boiling  point  of  the  same  liquid  is  constant,  so  long  as  Boiling 
the  necessary  conditions  are  preserved  ; but  it  is  liable  to  be  affected  P°jj^ 
by  several  circumstances.  The  nature  of  the  vessel  has  some  in  flu-  same  cir_ 
ence  upon  it.  Thus  Gay  Lussac  observed  that  pure  water  boils  pre- cumstan- 
cisely  at  212°  in  a metallic  vessel  and  at  214°  in  one  of  glass.  It  isces‘ 
likewise'  affected  by  the  presence  of  foreign  substances.  Bostock 
found  that  ether,  heated  in  a glass  vessel,  had  its  boiling  point  lower- 
ed nearly  50°  by  introducing  a few  chips  from  a cedar  pencil,  and 
alcohol  of  s.  g.  849  had  its  boiling  point  reduced  by  a similar  cause 
between  30°  and  40°.  The  boiling  point  of  water,  heated  in  a glass 
vessel,  was  brought  down  4°  or  5°  by  the  same  means. * By  put- 
ting coils  of  wire  into  liquids,  heated  in  glass  vessels  with  a view  to 
distillation,  they  are  made  to  boil  readily,  quietly  and  some  degrees 
lower  than  they  would  otherwise  do.  It  is  of  course  necessary  to 

use  a metal  which  will  not  be  acted  upon  by  the  liquid. 

187.  A circumstance  which  has  great  influence  over  the  boiling 

point  and  vaporization  of  fluids  is  variation  of  pressure.  By  the  pres?ure. 
mere  removal  of  atmospheric  pressure,  ether  will  be  converted  into 
vapour  at  the  common  temperature  of  the  atmosphere. 

Into  a glass  tube,  about  six  inches  long,  and  half  an  inch  in  diameter,  put  a gxp 
teaspoonful  of  ether,  and  fill  up  the  tube  with  water;  then,  pressing  the  thumb 
on  the  open  end  of  the  tube,  place  it,  inverted,  in  a jar  of  water.  Let  the  whole 
be  set  under  the  receiver  of  an  air-pump,  and  exhaust  the  air.  The  ether  will  be 
changed  into  gas,  which  will  expel  the  water  entirely  from  the  tube.  On  re-ad- 
mitting the  air  into  the  receiver,  the  gas  is  again  condensed  into  a liquid  form. 

From  the  experiments  of  the  late  Prof.  Bobison  it  appears  that  Boiling 
liquids  boil  in  a vacuum  at  a temperature  140°  lower  than  in  the  P™nt  m va' 
open  air.t  Thus  water  boils  at  72°  F.,  alcohol  at  36,°  and  ether  at 
— 44°.  This  proves  that  a liquid  is  not  necessarily  hot  because  it 


Ann.  of  Philos.  N.  S.  ix.  196. 


t Black’s  Lectures , Vol.  i.  p,  151. 


56 


Caloric. 


Chap.  I 


Effect  of 
chirtiges  of 
density  of 
the  air. 
Altitudes 
determined 
by  the 
boiling 
point. 


Example  of 
diminished 
pressure  fa- 
cilitating 
ebullition. 

Exp. 


boils.  The  heat  of  the  hand  is  sufficient  to  Fi*  ^ 

make  ether  boil  in  a vacuum,  as  is  exem- 
pi i fied  by  the  Pulse  Glass. 

188.  Even  the » ordinary  variations  in  the  weight  of  the  air,  as 
measured  by  the  barometer,  are  sufficient  to  make  a difference  in  the 
boiling  point  of  water  of  several  degrees.  When  the  barometer  is 
at  28  inches,  water  will  boil  at  the  temperature  of  208,43°,  when  at 
30  inches  at  212°,  and  when  at  31  at  213,76°.  At  the  top  of  Mount 
Blanc,  Saussure  found  that  it  boiled  at  187°,  so  that  the  heights  of 
mountains,  and  even  of  buildings,  may  be  calculated  by  reference 
to  the  temperature  at  which  water  boils  upon  their  summits.* 

The  following  apparently  paradoxical  experiment  also  illustrates 
the  influence  of  diminished  pressure  in  facilitating  ebullition. 

Fig.  39. 


Insert  a stop  cock  securely  into  the  neck  of  a Florence  flask,  Fig. 
39?  containing  a little  water,  and  heat  itover  a lamp  till  the  water 
boils,  and  the  steam  freely  escapes  by  the  open  stop  cock  ; then 
suddenly  remove  the  lamp  and  close  the  cock  The  water  will 
soon  cease  to  boil ; but  if  plunged  into  a vessel  of  cold  water,  ebul- 
lition instantly  recommences,  but  ceases  if  the  flask  be  held  near 
the  fire  : the  vacuum  in  this  case  being  produced  by  the  condensa- 
tion of  the  ste&m.t 


Example  of  189.  Water  cannot  be  heated  under  common  circumstances  beyond 
ry^flbct'of  212°  F.  because  it  then  acquires  such  an  expansive  force  as  enables  it 
pressure,  to  overcome  the  atmospheric  pressure,  and  to  fly  off  in  the  form  of 
vapour.  But  if  subjected  to  sufficient  pressure,  it  may  be  heated  to 
any  extent  without  boiling.  The  elasticity  of  steam  increases  in  a 
greater  ratio  than  the  temperature  at  which  it  is  produced  . thus  if  it  be 


1 at  212°  I 4 at  293.7  I 16  at  398.48  Fig.  49. 

it  is  2 “ 250.5  | 8 “ 341.78  | 24  “ 435.57  G 

Or  steam  at  these  temperatures,  has  2,  4, 8,  16,  and 
24  times  the  elastic  force  of  steam  at  212°. 4 


* Wollaston  has  described  the  method  of  constructing  a 
thermometer  of  extreme  delicacy,  applicable  to  these  pur- 
poses.* 

t The  experiment  may  be  varied  by  placing  the  flask  in 
an  inverted  position  in  the  ring  of  a retort-stand  and  blow- 
ing upon  it  with  a pair  of  bellows. 

M«rcei’«  «ppa-  * For  making  experiments  on  this  suby  ct,  the  apparatus, 
r«tu«.  represented  Fig.  40,  contrived  hy  Marcet,  will  be  found  ex- 

tremely useful,  o is  a strong  brass  globe,  composed  of  two 
hemispheres  screwed  together  with  flanches  ; a portion  of 
quicksilver  is  introduced  into  it,  and  it  is  then  about  half 
hlled  with  water,  b is  a barometer  tube  passing  through  a 
sleam-tight  collar,  and  dipping  into  the  quicksilver  at  the 
bottom  of  the  globe,  c is  a thermometer  graduated  to  ahout 
400°,  and  also  passing  through  an  air-light  collar,  d is  a 
stop  cock,  and  e a large  spirit  lamp.  The  whole  is  supported 
upon  the  brass  frame  and  stand  f.  Upon  applying  neat  to 
this  vessel,  the  stop  cock  being  closed  as  soon  as  the  water 
boils,  it  will  be  fouud  that  the  temperature  of  the  water  and 
its  vapour  increases  with  the  pressure,  which  is  measured 
by  the  ascent  of  the  mercury  in  the  barometer  tube.  The 
thermometer  under  atmospheric  pressure  being  at  212°,  will 
be  elevated  to  217°  under  a pressure  of  five  inches  of  mer- 
cury, and  to  242°  under  a pressure  of  30  inches,  or  therea- 
bouts ; each  inch  of  mercury  producing  by  its  pressure  a rise 
of  about  1°  in  the  thermometer.  The  barometer  tube  also 
serves  the  purpose  of  a safety-valve,  the  strength  of  the  brass 
globe  being  such  as  to  resist  a greater  pressure  than  that  of 
one  atmosphere. 

*Pk\l.  Tmns.  1817. 


c 


57 


Freezing  of  Mercury. 


190.  Evaporation  as  well  as  ebullition  consists  in  the  formation  of  Sect,  hi, 
vapour,  and  the  only  assignable  difference  between  them  is,  that  the  Evapora- 
one  takes  place  quietly,  the  other  with  the  appearance  nf  boiling.  tion- 
Evaporation  occurs  at  common  temperatures.  This  fact  may  be 
proved  by  exposing  water  in  a shallow  vessel  to  the  air  for  a few  days, 

when  it  will  gradually  diminish,  and  at  last  disappear  entirely. 

Most  liquids,  if  not  all  of  them,  are  susceptible  of  this  gradual  dissi- 
pation ; and  it  may  also  be  observed  in  some  solids,  as  for  example 
in  camphor.  Evaporation  is  much  more  rapid  in  some  liquids  than 
in  others,  and  it  is  always  found  that  those  liquids,  the  boiling  point 
of  which  is  lowest,  evaporate  with  the  greatest  rapidity.  Thus  alco- 
hol, which  boils  at  a lower  temperature  than  water,  evaporates  also 
more  freely  ; and  ether,  whose  point  of  ebullition  is  yet  lower  than 
that  of  alcohol,  evaporates  with  still  greater  rapidity. 

The  chief  circumstances  that  influence  the  process  of  evaporation 
are  extent  of  surface,  and  the  state  of  the  air  as  to  temperature,  dry- 
ness, stillness,  and  density. 

191.  The  conversion  of  a liquid  into  vapour  is  always  attended  Sensible, or 
with  great  loss  of  thermometric  heat ; and  as  liquids  may  be  regarded  ela*^ 
as  compounds  of  solids  and  heat,  so  vapours  may  be  considered  as.  tent. 
consisting  of  a similar  combination  of  heat  with  liquids ; in  other 

words,  a great  quantity  of  heat  becomes  latent  during  the  formation^ 
of  vapour. 


Moisten  a thermometer  with  alcohol,  or  with  ether,  and  expose  it  to  the  air,  g t 
repeating  these  operations  alternately.  The  mercury  of  the  thermometer  will  ‘ " 
sink  at  each  exposure,  because  the  volatile  liquor,  during  the  evaporation,  robs 
it  of  its  heat.  In  this  way,  (especially  with  the  aid  of  an  apparatus,  described 
by  M.  Cavallo,  in  the  Philosophical  Transactions,  1781,  p.  509,)  water  may  be 
frozen,  in  a thin  and  small  glass  ball,  by  means  of  ether.  The  same  effect  may 
be  obtained,  also,  by  immersing  a tube,  containing  water  at  the  bottom,  in  a glass 
of  ether,  which  is  to  be  placed  under  the  receiver  of  an  air  pump  ; or  the  ether 
may  be  allowed  to  float  on  the  surface  of  the  water.  During  the  exhaustion 
of  the  vessel,  the  ether  will  evaporate  rapidly,  and,  robbing  the  water  of  heat, 
will  completely  freeze  it;  thus  exhibiting  the  singular  spectacle  of  two  fluids  in 
contact  with  each  other,  one  of  which  is  in  the  act  of  boiling,  and  the  other  of 
freezing,  at  the  same  moment. 


By  a little  modification  of  the  experiment,  mercury  itself,  which  Marcet’ 
requires  for  congelation  a temperature  of  almost  40°  below  0 of  F.?  method  of 
may  be  frozen,  as  was  first  shown  by  Marcet.'^ 


freezing 

mercury. 


Ah 


* A conical  receiver,  (Fig.  41,)  open  at  the  top,  is  placed  on  the  Fig.  41. 
plate  of  an  air-pump,  and  a small  tube  with  a cylindrical  bulb  at 
its  lower  end,  containing  mercury,  is  suspended  within  the  receiver, 
through  the  aperture,  by  means  of  a brass  plate,  perforated  in  its  cen- 
tre, and  fitting  the  receiver  air-tight.,  when  laid  upon  its  open  neck. 

The  tube  passes  through  this  plate  to  which  it  is  fitted  by  a leather 
adjustment,  or  simply  by  a cork  secured  withsealing  wax.  The  bulb 
is  then  wrapped  up  in  a little  cotton  wool,  or,  what  is  better,  in  a 
small  bag  of  fine  fleecy  hosiery,  in  which  a small  spirit  thermometer 
graduated  below  40°  F.,  may  also  be  included,  and  after  being  dipped 
into  sulphuret  of  carbon  or  ether,*  the  apparatus  is  quickly  placed 
under  the  receiver,  which  is  exhausted  as  rapidly  as  possible.  In 
two  or  three  minutes,  the  temperature  sinks  to  about  45Q  below  0,  at 
which  moment  the  quicksilver  in  the  stem  suddenly  descends  with 

great  rapidity.  If  it  be  desired  to  exhibit  the  mercury  in  a solid  1 ' 

state,  common  tubes  may  be  used,  which  have  originally  been  about 

an  inch  in  diameter,  but  have  been  flattened  by  pressure,  when  softened  by  the  blow- 
pipe. The  experiment  succeeds,  when  the  temperature  of  the  room  is  as  high  as 
+ 40°  Fahrenheit.  H-  126. 

* In  exhausting  a vessel  containing  either  of  these  fluids,  the  valves  of  the  air  pump  should  be 
metallic. 

8 


58 


Caloric. 


Chap *  *•  192.  The  loss  of  sensible  heat  attending  the  formation  of  vapour, 

Tempera-  is  proved  by  the  well  known  fact  that  the  temperature  of  steam  is 
steam^  precisely  the  same  as  that  of  the  boiling  water  from  which  it  rises ; 

so  that  all  the  heat  which  enters  into  the  liquid,  is  solely  employed 
in  converting  a portion  of  it  into  vapour,  without  affecting  the  tem- 
perature of  either  in  the  slightest  degree,  provided  the  latter  is  per- 
mitted to  escape  with  freedom.  The  heat  which  then  becomes  latent, 
to  use  the  language  of  Black,  is  again  set  free  when  the  vapour  is 
condensed  into  water.  The  exact  quantity  of  heat  rendered  insensi- 
ble by  vaporization,  may,  therefore,  be  ascertained  by  condensing  the 
vapour  in  cold  water,  and  observing  the  rise  of  temperature  which 
ensues.  From  the  experiments  of  Black  and  Watt,  conducted  on  this 
principle,  it  appears  that  steam  of  212°, in  being  condensed  into  water 
of  212°,  gives  out  as  much  heat  as  would  raise  the  temperature  of  an 
% equal  weight  of  water  by  950  degrees,  all  of  which  had  previously  ex- 

isted in  the  vapour  without  being  sensible  to  a thermometer. 

Latent  heat  The  latent  heat  of  steam  and  several  other  vapours  has  been  exa- 
oi‘  mined  by  Ure,  whose  results  are  contained  in  the  following  table. 

(Phil.  Trans . 1818.) 


Latent  Heat. 


Vapour  of  water  at  its  boiling  point 
Alcohol  . 

Ether  . 

Petroleum 
Oil  of  turpentine 
Nitric  acid 
Liquid  ammonia 
Vinegar,  . 


967° 

442 

302.379 

177.87 

177.87 

531.99 

837.28 

875* 


193.  The  large  quantity  of  heat,  latent  in  steam,  renders  its  ap- 


When  a jet  of  liquid  carbonic  acid  is  directed  upon  mercury,  it  is  so  rapidly  vaporized 
that  the  mercury  is  frozen.  The  pipes  connected  with  the  fountains  from  which  soda 
water  is  drawn,  are  often  closed  by  ice,  formed  on  the  sudden  escape  and  expansion  of 
the  last  portion  of  water  and  compressed  gas. 


Henry’s  appa- 
ratus. 


* The  small  boiler,  represented  in  Fig.  42,  taken  from  Henry’s  Elements  of  Che- 
mistry, may  be  conveniently  Fig.  42. 

employed  in  experiments  on 
the  latent  heat  ol  steam. 

For  this  purpose  the  tubee 
must  be  screwed  on  the  stop- 
cock b , and  immersed  into  the 
glass  of  water  f.  The  cock  c 
being  closed,  the  steam  arising 
from  the  boiling  water  a will 
pass  into  the  cold  watery*,  the 
temperature  of  which  will  be 
much  augmented  by  its  con* 
densation.  Ascertain  the  in- 
crease of  temperature  and 
weight,  and  the  result  will 
show  how  much  a given  weight 
of  water  has  had  its  tempera- 
ture raised  by  a certain  weight 
of  condensed  steam.  To  ano- 
ther quantity  of  water  of  the 
same  weight  and  temperature 
as  that  in  the  jar  at  the  outset 
of  the  experiment,  add  a quan- 
tity of  water  at  212°,  equal  in  weight  to  the  condensed  steam;  it  will  be  found,  on 
comparing  the  resulting  temperatures,  that  a given  weight  of  steam  has  produced,  by 
its  condensation,  a much  greater  elevation  of  temperature  than  the  same  quantity  of 
boiling  water. 


Steam . 


59 


plication  extremely  useful  for  practical  purposes.  Thus  water  may  be  Sect,  iii. 
heated  at  a considerable  distancefrom  the  conducting  pipe  e.  (Fig.  42.)  Economical 
This  furnishes  us  with  a commodious  method  of  warming  the  water  gtseea^[ 
of  baths,  which,  in  certain  cases  of  disease,  it  is  of  importance  to  have 
near  the  patient’s  bed-room  ; for  the  boiler,  in  which  the  water  is 
heated,  may  thus  be  placed  on  the  ground  floor,  or  in  the  cellar  of  a 
house  ; and  the  steam  conveyed  by  pipes  into  an  upper  apartment. 

Steam  may  also  be  applied  to  the  purpose  of  heating  or  evaporating 
water,  by  a modification  of  the  apparatus.*  In  breweries  and  other  in  some 
manufactories,  where  large  quantities  of  warm  and  boiling  water  are  arts» 
consumed  it  is  frequently  heated  by  conveying  steam  into  it,  or  by 
suffering  steam-pipes  to  traverse  the  vessels  or  by  employing  double 
vessels,  a plan  adopted  with  particular  advantage  in  the  preparation 
of  medicinal  substances.  Where  a higher  temperature  than  212°  is 
required  it  is  necessary  to  employ  steam  under  adequate  pressure. 

194.  The  perfect  transparency  of  steam,  and  also  two  other  impor- Steam  is 
tant  properties,  on  which  depends  its  use  as  a moving  power,  viz.  its  J^spa“ 
elasticity  and  its  condensibility  by  a reduced  temperature,  are  beau- 
tifully shown  by  a little  apparatus  contrived  by  Wollaston. 

It  consists  of  a glass  tube  (Fig.  43)  about  6 inches  long 
and  | inch  bore,  as  cylindrical  as  possible,  and  blown  out  a 
little  at  the  lower  end.  It  has  a wooden  handle,  to  which  is 
attached  a brass  clip  embracing  the  tube  ; and  within  is  a 
piston,  which,  as  well  as  its  rod,  is  perforated,  as  shown  by 
the  dotted  lines.  This  canal  may  be  occasionally  opened 
or  closed  by  a screw  at  the  top  : and  the  piston  rod  is  kept 
in  the  axis  of  the  cylinder  by  being  passed  through  a piece 
of  cork  fixed  at  the  top  of  the  tube.  When  the  instrument 
is  used,  a little  water  is  put  into  the  bottom ; the  piston  is 
then  introduced  with  its  aperture  left  open ; and  the  water 
is  heated  over  a spirit  lamp.  The  common  air  is  thus  expelled 
from  the  tube,  and  when  this  may  be  supposed  to  be  effect- 
ed, the  aperture  in  the  rod  is  closed  by  the  screw.  On  ap- 
plying heat,  steam  is  produced,  which  drives  the  piston  up- 
wards. On  immersing  the  bulb  in  water,  or  allowing  it  to 


* Fig  42,  g represents  the  apparatus  for  boiling  water  by  the  condensation  of  steam, 
without  adding  to  its  quantity  ; a circumstance  occasionally  of  considerable  importance. 

The  steam  is  received  between  the  vessel,  which  contains  the  water  to  be  heated,  and  an 
exterior  case ; it  imparts  its  caloric  to  the  water,  through  the  substance  of  the  vessel ; 
is  thus  condensed,  and  returns  to  the  boiler  by  the  perpendicular  pipe.  An  altera- 
tion of  the  form  of  the  vessel  adapts  it  to  evaporation  (Fig.  42,  h).  This  method  of 
evaporation  is  admirably  suited  to  the  concentration  of  liquids,  that  are  decomposed, 
or  injured  by  a higher  temperature  than  that  of  boiling  water,  such  as  medicinal  ex- 
tracts ; to  the  drying  of  precipitates,  &c.  In  the  employment  of  either  of  these  vessels, 
it  is  expedient  to  surround  it  with  some  slow  conductor  of  heat.  On  a small  sca'e 
a few  folds  of  woollen  cloth  are  sufficient ; and  when  the  vessel  is  constructed  of  a 
large  size  for  practical  use,  this  purpose  is  served  by  the  brick  work  in  which  it  it. 
placed.  H.  1.  135. 

A very  convenient  apparatus  for  drying  precipitates,  &c.  by  steam  is  described  by  Ure.  tire’s  drying 
A square  tin  box,  about  18  inches  long,  12  broad,  and  6 deep,  has  its  bottom  hollowed  a 
little  by  the  hammer  towards  its  centre,  in  which  a round  hole  is  cut  of  5 or  6 inches 
diameter.  Into  this  a tin  tube,  3 or  4 inches  long,  is  soldered.  This  tube  is  made  to 
fit  tightly  into  the  mouth  of  a common  teakettle,  which  has  a folding  handle.  The 
top  of  the  box  has  a number  of  circular  holes  cut.  into  it,  of  different  diameters,  in 
which  evaporating  capsules  are  placed.  When  the  kettle,  filled  with  water,  and  with 
its  nozzle  corked,"  is  set  on  a stove,  the  vapour  playing  on  the  bottoms  of  the  capsules, 
heats  them,  to  any  required  temperature;  and  being  itself  continually  condensed  runs 
back  into  the  kettle.  The  orifices  not  in  use  may  be  closed  with  tin  lids.  In  drying- 
precipitates,  the  tube  of  the  glass  funnel  should  be  corked  up,  and  the  funnel  be  placed, 
with  its  filter,  directly  into  the  proper  sized  opening.  For  drying  red  cabbage,  violet 
petals,  &c.  a tin  tray  is  provided,  which  fits  close  on  the  top  of  the  box,  within  . the  rim 
which  goes  about  it.  The  round  orifices  are  left  open  when  this  tray  is  applied. 

(Diet.  Chem.  291.) 


Fig.  43, 


60 


Caloric. 


Chap.  I. 


Reduction 
of  tempera- 
ture by  e- 
vaporation. 

Leslie’s 
method  of 
freezing 
water. 


Wollas- 
ton’s Cryo- 
phorus. 


oool  spontaneously,  a vacuum  is  produced  in  the  tube,  and  the  piston  is  forced 
downwards  by  the  weight  of  the  atmosphere.  These  appearances  may  be  alter- 
nately produced  by  repeatedly  heating  and  cooling  the  water  in  the  ball  of  the 
instrument. 

In  the  original  steam  engine,  the  vapour  tvas  condensed  in  the 
cylinder,  as  it  is  in  the  glass  tube;  but  in  the  engine  as  improved  by 
Watt,  the  steam  is  pumped  into  a separate  vessel,  and  there  con- 
densed ; by  which  the  loss  of  heat,  occasioned  by  cooling  the  cylin- 
der every  time,  is  avoided. 

195.  Liquids  assume  the  aeriform  state  much  more  rapidly  under 
a diminished  pressure,  especially  if  the  vapour  which  is  formed,  be 
condensed  as  soon  as  it  is  produced,  so  as  to  maintain  the  vacuum  ; 
and  the  cold  produced  is  very  great. 

On  this  principle  depends  Leslie’s  ingenious  mode  0/  freezing 
water,  in  an  atmosphere  of  any  common  temperature,  by  producing  a 
rapid  evaporation  from  the  surface  of  the  water  itself.  The  water  to 
be  congealed  is  contained  in  a shallow  porous  vessel,  which  is  sup- 
ported above  another  vessel,  containing  strong  sulphuric  acid,  or  dry 
chloride  of  calcium  ; or  even  dried  garden  mould  or  parched  oatmeal. 
Any  substance,  indeed,  that  powerfully  attracts  moisture,  may  be 
applied  to  this  purpose.  The  whole  is  covered  by  the  receiver  of  an 
air  pump,  which  is  rapidly  exhausted  ; and  as  soon  as  this  is  effected, 
crystals  of  ice  begin  to  shoot  in  the  water,  and  a considerable  quan- 
tity of  air  makes  its  escape,  after  which  the  whole  of  the  water  be- 
comes solid.  The  rarefaction  required  is  to  about  100  times  ; but  to 
support  congelation,  after  it  has  taken  place,  20  or  even  10  times  are 
sufficient.  The  sulphuric  acid  becomes  very  warm ; and  it  is  re- 
markable, that,  if  the  vacuum  be  kept  up,  the  ice  itself  evaporates. 
In  fi  ve  or  six  days,  ice  of  an  inch  in  thickness  will  entirely  disappear. 
The  acid  continues  to  act,  till  it  has  absorbed  an  equal  volume  of  water.* 

In  this  interesting  process,  if  it  were  not  for  the  sulphuric  acid,  an 
atmosphere  of  aqueous  vapour  would  fill  the  receiver;  and,  pressing 
on  the  surface  of  the  water,  would  prevent  the  further  production  of 
vapour.  But  the  steam,  which  rises,  being  condensed  the  moment  it  is 
formed,  the  evaporation  goes  on  very  rapidly,  and  has  no  limits  but  the 
quantity  of  the  water,  and  the  diminished  concentration  of  the  acid. 

19G.  It  is  on  the  same  principle,  that  the  instrument  invented  by 
Wollaston,  and  termed  by  him  the  Cryophorns , or  Frostbearer , is 
founded.  (Fig.  45.)  When  an  instrument  of  this  kind  is  well  prepared,  if 
the  empty  ball  be  immersed  in  a mixture  of  snow  and  salt,  the  water  in 


♦This  beautiful  experiment  is  not  successful  with  pumps  on 
the  usual  construction.  Pumps  are  now  made  by  Chamberlain  of 
Boston,  which  produce  the  effect  with  ease  and  rapidity.  See 
Frontispiece. 

An  elegant  manner  of  making  the  experiment  is  to  cover  the 
vessel  of  water  (Fig.  44,  a)  with  a plate  of  metal  or  glass,  fixed  to 
the  end  of  a sliding  wire  b , which  must  pass  through  the  neck  of 
the  receiver,  and  be  at  the  same  time  air  tight,  and  capable  of  be- 
ing drawn  upwards.  When  the  receiver  is  exhausted,  the  water 
will  continue  fluid,  till  the  cover  is  removed,  when,  in  less  than 
five  minutes,  needle-shaped  crystals  of  ice  will  shoot  through  it, 
and  the  whole  will  soon  become  frozen. 


Fig.  44. 


Effects  of  Evaporation.  61 

the  other  ball,  though  at  the  distance  of  two  or  three  feet*  will  be  Sect. hi. 
frozen  solid  in  the  course  of  a very  few  minutes. # 

197.  The  disappearance  of  heat  that  accompanies  vaporization  was 
explained  by  Black,  in  the  way  already  mentioned  under  the  head  of 
liquefaction,  (177.) 

The  variation  of  volume  and  elasticity  in  vapours  is  attended,  as 
in  gases,  with  a change  of  specific  heat  and  a consequent  variation  of 
temperature.  Thus  when  steam,  highly  heated  and  compressed  in  a 
strong  boiler,  is  permitted  to  escape  by  a large  aperture,  the  sudden 
expansion  is  attended  with  a great  loss  of  sensible  heat : its  tempera- 
ture instantly  sinks  so  much,  that  the  hand  may  be  held  in  the  cur- 
rent of  vapour  without  inconvenience.  The  same  principle  accounts 
for  the  fact,  first  ascertained  by  Watt*  that  distillation  at  a low  tem- 
perature is  not  attended  with  any  saving  of  fuel.  For  when  water 
boils  at  a low  temperature  in  a vacuum,  the  vapour  is  in  a highly 
expanded  statej  and  contains  more  insensible  heat  than  steam  of 
greater  density. 

198.  In  many  natural  operations  the  conversion  of  water  into  va- 
pour, and  the  condensation  of  vapour  in  the  form  of  dew  and  rain,  is 
a process  of  the  utmost  importance,  and  tends  considerably  to  the 
equalization  of  temperature  over  the  globe. 

Water,  as  has  been  seen  (192)  in  passing  into  vapour  from  heat, 
absorbs  caloric  without  increasing  in  temperature;  this  vapour  as- 
cends in  the  atmosphere  ; when  the  heat  diminishes,  or  when  wafted 
to  colder  regions,  it  is  condensed,  and  gives  out  the  caloric  it  had  ab-  Tempera  - 
sorbed.  In  seasons  or  situations  where  the  cold  becomes  still  more  tljreo 
intense,  water  is  congealed;  and  in  suffering  this  change  it  evolves  fquaeijZed. 
caloric  (180)  to  moderate  the  progressive  reduction  of  temperature. 

When  warmth  is  restored,  it  returns  to  the  liquid  state,  absorbs  palo- 
ric,  and  retards  the  approaching  heat.  The  transition  of  seasons  is 
thus  moderated  ; sudden  and  extreme  variations  are  guarded  against, 
and  the  temperature  of  the  globe  everywhere  preserved  more  uni- 
form. M.  1.480. 

199.  As  evaporation  goes  on  to  a certain  extent  even  at  low  tem- 


* It  may  be  formed  by  taking  a glass  tube,  having  Fig.  45. 

an  internal  diameter  about  £th  of  an  inch*  the  tube  be- 
ing bent  to  a right  angle  at  the  distance  of  half  an  inch 
from  each  ball  (Fig.  45).  One  of  these  balls  should  be  about 
Jd  filled  with  water,  and  the  other  should  be  as  perfect  a 
vacuum  as  can  readily  be  obtained,  the  mode  of  effecting  which  is  well  known  to 
those  accustomed  to  blow  glass.  One  of  the  balls  is  made  to  terminate  in  a capillary 


3 


tube;  and  when  the  water  in  the  other  ball  has  been  boiled  over 
a lamp  a considerable  time,  till  all  the  air  is  expelled,  the  capillary 
extremity,  through  which  the  steam  is  still  issuing  with  violence,  is 
held  in  the  flame  of  the  lamp,  till  the  force  of  the  vapour  is  so  far 
reduced,  that  the  heat  of  the  flame  has  power  to  seal  it  hermetically. 

The  experiment  may  be  rendered  even  more  striking,  if  per- 
formed according  to  Marcet’s  modification  of  it : the  empty  ball  cov- 
ered with  a little  moist  flannel,  is  to  be  suspended  in  the  manner 
shown  in  Fig.  46,  within  a receiver,  over  a shallow  vessel  of  strong 
sulphuric  acid,  and  the  receiver  is  then  to  be  exhausted.  In  both 
cases  the  vapour  in  the  empty  bail  is  condensed  by  the  common  opera- 
tion of  cold  ; and  the  vacuum  produced  by  this  condensation  gives 
opportunity  for  a fresh  quantity  to  arise  from  the  opposite  ball,  with 
a proportional  reduction  of  the  temperature  of  its  contents. 


Fig.  46. 


62 


Caloric. 


Hygrome- 

ters, 


Saussure’s, 


Chap.  I.  peratures,  it  is  probable  that  the  atmosphere  is  never  absolutely  free 
from  vapour. 

The  quantity  of  vapour  present  in  the  atmosphere  is  very  variable, 
in  consequence  of  the  continual  change  of  temperature  to  which  the 
air  is  subject.  But  even  when  the  temperature  is  the  same,  the 
quantity  of  vapour  is  still  found  to  vary  ; for  the  air  is  not  always  in 
a state  of  saturation.  This  variable  condition  of  the  atmosphere  as 
to  saturation  is  ascertained  by  the  hygrometer. 

200.  A great  many  hygrometers  have  been  invented  ; but  they  may 
all  be  referred  to  three  principles.  The  construction  of  the  first  kind  of 
hygrometer  is  founded  on  the  property  possessed  by  some  substances 
of  expanding  in  a humid  atmosphere,  owing  to  a deposition  of 
moisture  within  them  ; and  of  parting  with  it  again  to  a dry  air,  and 
in  consequence  contracting.  Of  these,  none  is  better  than  the  hu- 
man hair,  which  not  only  elongates  freely  from  imbibing  moisture, 
but,  by  reason  of  its  elasticity,  recovers  its  original  length  on  drying. 
The  hygrometer  of  Saussure  is  made  with  this  material. 

The  second  kind  of  hygrometer  points  out  the  opposite  states  of 
dryness  and  moisture  by  the  rapidity  of  evaporation.  Water  does 
not  evaporate  at  all  when  the  atmosphere  is  completely  saturated 
with  moisture  ; and  the  freedom  with  which  it  goes  on  at  other 
times,  is  in  proportion  to  the  dryness  of  the  air.  The  hygrometric 
condition  of  the  air  may  be  determined,  therefore,  by  observing  the 
rapidity  of  evaporation.  The  most  convenient  method  of  doing  this 
is  by  covering  the  bulb  of  a thermometer  with  a piece  of  silk  or  linen, 
moistening  it  with  water,  and  exposing  it  to  the  air.  The  descent  of 
the  mercury,  or  the  cold  produced,  will  correspond  to  the  quantity  of 
vapour  formed  in  a given  time.  Leslie’s  hygrometer  is  of  this  kind. 

The  third  kind  of  hygrometer  is  on  a principle  entirely  different 
from  the  foregoing.  When  the  air  is  saturated  with  vapour,  and  any 
colder  body  is  brought  into  contact  with  it,  deposition  of  moisture 
immediately  takes  place  on  its  surface.  This  is  often  seen  when  a 
glass  of  cold  spring  water  is  carried  into  a warm  room  in  summer ; 
and  the  phenomenon  is  witnessed  in  the  formation  of  dew,  the 
moisture  appearing  on  those  substances  only  which  are  colder  than 
the  air. 

201.  Until  the  experiments  of  Wells*  the  deposition  of  dew  and 
Hoar  frost.  ]10ar  frost  had  been  supposed  to  depend  entirely  upon  the  reduction 

of  temperature  in  the  air  during  the  night,  and  the  consequent  pre- 
cipitation of  its  moisture  to  the  earth.  Wells  has  shown  that  the 
deposition  of  dew  and  hoar  frost,  is  the  consequence  of  the  radiation 
of  caloric  from  the  surface  of  the  earth,  and  that,  under  favourable 
circumstances,  the  temperature  of  the  ground,  especially  when  its 
covering  is  formed  of  some  substance  that  radiates  freely,  as  grass,  is 
several  degrees  below  that  of  the  atmospheric  stratum,  a few  feet 
above  it.  It  is  this  diminished  temperature  of  the  earth’s  surface, 
that  occasions  the  depositions  of  dew  and  hoar  frost,  which  are 
always  observed  to  be  most  abundantly  formed  under  a clear  un- 
clouded sky;  a covering  of  clouds  serves  as  a mantle  to  the  earth, 
and  prevents  the  free  escape  of  radiant  caloric,  hence  the  advantage 
of  snow  and  artificial  coverings  in  protecting  plants. 


Leslie’s. 


Dew  and 


Eseay  on  Detr,  <$y. 


Conducting  Powers. 


63 


The  temperature  at  which  dew  begins  to  be  deposited  is  called  the  Sect,  hi. 
dew  point,  for  determining  which  a very  ingenious  instrument  has  Dewpoint, 
been  contrived  by  Daniell.^  {Jour.  Royal  Institut.  Yol.  8.) 

202.  When  different  bodies  are  exposed  to  the  same  source  of  Conducting 
heat,  they  suffer  it  to  pass  through  them  with  very  different  degrees  todies  for 
of  velocity,  or  they  have  various  conducting  powers  in  regard  to  heat,  caloric, 
Among  solid  bodies,  metals  are  the  best  conductors  ; and  silver,  gold, 

tin  and  copper,  are  better  conductors  than  platinum,  iron,  and  lead. 

Next  to  the  metals,  we  may,  perhaps,  place  the  diamond  and  topaz  ; 
then  glass  ; then  siliceous  and  hard  stony  bodies  in  general ; then 
soft  and  porous  earthy  bodies,  and  wood  ; and  lastly,  down,  feathers, 
wool,  and  other  porous  articles  of  clothing. 

203.  To  exhibit  the  general  fact,  small  cones  of  the  different  sub-  Apparatus 
stances  may  be  used  about  three  inches  high,  and  half  an  inch  in  [•)„glllustra' 
diameter  at  their  bases : these  may  be  tipped  at  the  apex  with  a 

small  piece  of  wax,  and  being  placed  on  a heated  metallic  plate,  will 
indicate  the  conducting  powers  by  the  relative  times  required  to  fuse 
the  wax,  which  will  be  inversely,  as  the  power  of  conducting  heat.f 

The  difference  between  the  conducting  power  of  the  diamond  and 
rock  crystal  or  glass,  is  shown  by  applying  the  tongue  to  those  sub- 
stances, when  the  former  feels  colder  than  the  latter.! 

204.  Rumford’s  experiments  on  the  conducting  power  of  several  Conducting 
substances  used  as  clothing,  offer  some  interesting  results.^  He  ^°0Yh[ngf 
found  that  a thermometer  enclosed  in  a tube  and  bulb  of  the  same  substances, 
shape,  but  large  enough  to  allow  of  an  inch  vacant  space  between 

the  two,  being  previously  heated,  required  576  seconds  to  cool  135°. 

When  16  grains  of  lint  were'  diffused  through  the  confined  air,  it 
took  1032  seconds  to  undergo  the  same  change  of  temperature  ; and 
1305  seconds,  with  the  same  weight  of  eider  down.  The  compres- 
sion of  flocculent  substances  to  a certain  extent,  renders  them  still 
inferior  conductors  ; thus,  when  the  space  which  in  the  above  expe- 
riments contained  16  grains  of  eider  down  was  filled  with  32,  and 
then  with  64  grains,  the  times  required  for  the  escape  of  60  degrees 
of  heat  were  successively  increased  ‘from  1305"  to  1475"  and 
1615". 

On  the  other  hand  to  show  the  effect  of  mere  texture , similar  Effect  of 
comparative  trials  were  made  of  the  conducting  powers  of  equal  texture, 
weights  of  raw  silk,  of  ravellings  of  white  taffeta,  and  of  common 
sewing  silk,  of  which  the  first  has  the  finest  fibre,  the  second  less 
fine,  and  the  third,  from  being  twisted  harder,  is  much  coarser. 


* A less  expensive  instrument  is  made  by  Pollock,  of  Boston ; it  is  a thermometer 
filled  with  ether,  having  two  bulbs  at  the  same  extremity  of  the  tube,  the  upper  one 
being  covered  with  muslin.  When  sulphuric  ether  is  dropped  upon  the  muslin,  the 
temperature  of  the  two  bulbs  falls,  and  a deposition  of  dew  becomes  visible  on  the 
lower  and  exposed  bulb.  The  degree  indicated  by  the  thermometer  at  that  instant  is 
the  dew  point* * * § 

t This  experiment  may  be  varied  by  attaching  small  pieces  of  phosphorus  to  the 
cones.  See  on  this  subject  ingenious  experiments  and  apparatus  by  Bache,  in  Am. 
Jour.,  xxviii.  320. 

tFrom  the  experiments  of  Mayer,  of  Erlangen,  (Ann.  de  Chirn.  tom.  xxx,)  it  would 
appear  that  the  conducting  powers  of  different  woods  are  in  some  measure  inversely  as 
their  specific  gravities,  water  being  assumed  as=  1. 

§ Phil.  Trans.  1792. 

* See  description  of  a Portable  Hygrometer,  Hayes,  in  Am.  Jour . Sci.  xvii.  351. 


64 


Caloric. 


Chap.  I. 


Practical 

application. 


Sensations 
of  heat  and 
cold 


Liquids  and 
gases  im- 
perfect con- 
ductors. 

Exp. 


Exp, 


Exp. 


The  difference  between  these  three  modifications  of  the  same  sub- 
stance is  very  striking,  the  raw  silk  detaining  the  heat  for  1824", 
the  taffeta  ravellings  1469  1 and  the  silk  thread  only  947 1 

205.  The  different  conducting  powers  of  bodies  in  respect  to  heat, 
are  shown  in  the  application  of  wooden  handles  to  metallic  vessels  ; 
or  a stratum  of  ivory  or  wood  is  interposed  between  the  hot  vessel  and 
the  metal  handle.  The  transfer  of  heat  is  thus  prevented.  Heat  is 
confined  by  bad  conductors  ; hence  clothing  for  cold  climates  com 
sists  of  woollen  materials  ; hence,  too,  the  walls  of  furnaces  are 
composed  of  clay  and  sand.  Confined  air  is  a very  bad  conductor  of 
heat ; hence  the  the  advantage  of  double  doors  to  furnaces,  to  pre- 
vent the  escape  of  heat ; and  of  a double  wall,  with  an  interposed 
stratum  of  air,  to  an  ice-house,  which  prevents  the  influx  of  heat 
from  without. 

206.  From  the  different  conducting  powers  of  bodies  in  respect  to 
heat,  arise  the  sensations  of  heat  and  cold  experienced  upon  ther  ap- 
plication to  our  organs,  though  their  thermometric  temperature  is 
similar.  Good  conductors  occasion,  when  touched,  a greater  sensa- 
tion of  heat  and  cold  than  bad  ones.  Metal  feels  cold  because  it 
readily  carries  off  the  heat  of  the  body  ; and  we  cannot  touch  a piece 
of  metal  immersed  in  air  of  a temperature  moderate  to  our  sense. 

207.  Liquids  and  gases  are  very  imperfect  conductors  of  heat,  and 
heat  is  generally  distributed  through  them  by  a change  of  specific 
gravity  ; by  an  actual  change  in  the  situation  of  their  particles. 

Take  a glass  tube,  ten  or  twenty  inches  long,  and  four  or  six  in  diameter. 
Pour  into  the  bottom  part,  for  about  the  depth  of  five  inches,  water  tinged  with 
litmus,  or  cabbage,  and  fill  up  the  tube  with  common  water,  pouring  on  the  lat- 
ter extremely  gently,  so  as  to  keep  the  two  strata  quite  distinct.  If  the  upper 
part  of  the  tube  be  first  heated,  the  coloured  liquor  will  remain  at  bottom  ; but 
if  the  tube  be  afterwards  heated  at  bottom,  the  infusion  will  ascend,  and  will 
tinge  the  whole  mass  of  fluid. 

A convenient  method  of  exhibiting  this  has  been  contrived 
by  Hare.  (Fig.  47.)  A glass  jar,  about  30  inches  in  height,  is 
supplied  with  as  much  colourless  water  as  will  rise  in  it  with- 
in a few  inches  of  the  brim.  By  means  of  a tube  descending 
to  the  bottom,  a small  quantity  of  blue  colouring  matter  is  in- 
troduced belotd  the  colourless  water,  sq  as  to  form  a stratum, 
as  represented  at  A in  the  annexed  cut  A stratum  different- 
ly coloured,  is  formed  in  the  upper  part  of  the  vessel,  as  at  B. 

A tin  cap,  supporting  a hollow  tin  cylinder,  closed  at  the  bot- 
tom, and  about  an  inch  less  in  diameter  than  the  jar,  is  next 
placed  as  it  is  seen  in  the  figure,  so  that  the  cylinder  may  be 
concentric  with  the  jar,  and  descend  about  3 or  4 inches  into 
the  water.  If  an  iron  heater  H while  red  hot,  be  placed 
within  the  tin  cylinder,  the  coloured  water  about  it  will  soon 
boil ; but  the  heat  penetrates  only  a very  small  distance  be-  ^ ^ 
low  the  tin  cylinder,  so  that  the  colourless  water,  and  the  1 ■ -*^R 

coloured  stratum,  at  the  bottom  of  the  vessel,  remain  undisturbed,  and  do  not 
mingle.  But  if  an  iron  ring  k be  placed  while  red  hot,  upon  the  iron  stand  which 
surrounds  the  jar  at  S,  S,  the  liquid  soon  rises,  in  beautiful  clouds,  until  it  en- 
counters the  warmer  and  lighter  particles  which  had  been  in  contact  with  the 
tin  cylinder.! 

Fill  a jar  with  hot  water  ; and  place  a cake  of  ice  on  the  surface  of  the  water. 
The  ice  will  soon  be  melted.  This  experiment  is  the  more  striking,  if  the  water 


* Aiken’s  Did.  art.  Caloric. 

t From  Hares’s  Engravings  and  description  of  Chemical  Apparatus , &c.  Part  1st, 
page  41. 


Fig.  47. 

Co)  H 


Radiation , 


65 


used  for  forming  the  cake  of  ice,  be  previously  coloured  with  litmus  ; for,  the  Sec.  Ill . 
descending  currents  of  cold  water  are  thus  made  apparent.  Rumford’s 

Substituting  water  of  the  temperature  of  11°  for  the  boiling  water  used  in  this  experi„ 
experiment,  Rumford  found,  that,  in  a given  time,  a much  greater  quantity  of  mept5- 
ice  was  melted  by  the  cooler  water.  This  appears,  on  first  view,  rather  paraT 
doxical.  The  fact,  however,  is  explained  by  the  remarkable  property  of  water, 
viz.  that  when  cooled,  below  40°,  it  ceases  to  contract,  and  experiences  on  the 
contrary,  an  enlargement  of  bulk.  Water,  therefore,  at  40°  (at  the  bottom  of 
which  is  a mass  of  ice  at  32°,)  is  cooled  by  contact  with  the  ice,  and  is  expan- 
ded at  the  same  moment.  It  therefore  ascends,  and  is  replaced  by  a heavier  and 
warmer  portion  from  above. 

208.  It  is  a consequence  of  the  same  property,  that  the  surface  of 
a deep  lake  is  sometimes  covered  with  ice,  even  when  the  water  be- 
low is  only  cooled  to  40°;  for  the  superficial  water  is  specifically  light- 
er than  the  warmer  water  beneath  it,  and  retains  its  place,  till  it  is 
changed  into  ice.  This  property  of  water  is  one  of  the  most  remark- 
able exceptions  to  the  law  of  expansion.  (153.) 

209.  From  the  fact  that  heat  applied  to  the  upper  surface  of  water, 
will  with  difficulty  make  its  way  downwards,  (207),  Rumford  was 
induced  to  deny  that  water  could  conduct  at  all. 

Let  an  air  thermometer  be  cemented  into  a glass  funnel  sup- 
ported as  represented  in  Fig.  48  ; cover  the  bulb  of  the  instru- 
ment with  water,  and  upon  the  surface  of  the  water  pour  a 
small  quantity  of  ether,.  The  ether  may  be  inflamed  and  the  air 
thermometer  will  not  be  sensibly  affected. 

210.  The  inference  that  water  is  a complete  non- 
conductor of  caloric  has  been  contradicted  by  the  sub? 
sequent  inquiries  of  Hope,  Thomson,  and  Murray. 

Though  they  all  admit  that  water  and  liquids  in 
general,  mercury  excepted,  possess  the  power  of  con- 
ducting caloric  in  a very  slight  degree.  The  follow- 
ing experiment  made  by  Murray  has  been  deemed  con- 
clusive. 

If  we  carefully  pour  hot  oil  upon  water  in  a tall  glass  jar,  with  delicate  ther-  „ 
mometers  placed  at  different  distances  under  the  surface,  it  will  be  found  that  • P' 
those  near  the  heated  surface  indicate  increase  of  temperature. 

It  might  here  be  said  that  the  heat  was  conducted  by  the  sides  of 
the  jar,  and  so  communicated  to  the  water;  to  obviate  such  objection 
Murray  made  the  experiment  in  a vessel  of  ice,  which  being  con- 
verted into  water  at  32°,  cannot  convey  any  degree  of  heat  above 
32°  downwards  ; yet  the  thermometers  were  affected,  as  in  the  for- 
mer trial.* 

211.  It  is  extremely  difficult  to  estimate  the  conducting  power  of  Aeriform 
aeriform  fluids.  Their  particles  move  so  freely  on  each  other,  that  fluids, 
the  moment  a particle  is  dilated  by  heat,  it  is  pressed  upwards  vvith 

great  velocity  by  the  descent  of  colder  and  heavier  particles,  so  that 
an  ascending  and  descending  current  is  instantly  established.  Be- 
sides, these  bodies  allow  a passage  through  them  by  radiation. 

212.  There  is  yet  another  mode  by  which  heat  passes  from  one  Radiation, 
body  to  another  ; and  as  it  takes  place  in  all  gases,  and  even  in 
vacuo,  it  is  inferred  that  the  presence  of  a medium  is  not  necessary 

to  its  passage.  This  mode  of  distribution  is  called  Radiation  of 
Heat,  and  the  heat  so  distributed  is  called  Radiant , ox  Radiated  Heat. 

A heated  body  suspended  in  the  air  cools,  or  is  reduced  to  an  equili- 

* See  Matther’s  Experiments  in  Amer.  Jour,  of  Sci.  xii.  368. 

9 


Fig-  48. 


Exp. 


Fluids  irm 
%./  perfect  cop? 
luctors- 


AJ 


66 


Caloric. 


Chap.  J. 

Course  of 

radiant 

caloric. 


Radiation, 
in  vacuo 


Influenced 
by  surface. 


Leslie’s  ex- 
periments. 


Bache;«  appa-’ 
raius. 


brium  with  surrounding  bodies,  in  three  ways;  first,  by  the  conduct- 
ing power  of  the  air,  the  influence  of  which  is  very  trifling  ; secondly, 
by  the  mobility  of  the  air,  in  contact  with  it ; and  thirdly,  by  radiation. 

213.  Radiant  caloric  passes  from  a hot  body  in  all  directions  in  right 
lines,  like  radii  drawn  from  the  centre  to  the  circumference  of  a circle. 

When  these  rays  fall  upon  the  surface  of  a solid  or  liquid  sub- 
stance, they  may  be  disposed  of  in  three  different  ways.  By  reflec- 
tion, by  absorption,  and  by  transmission. 

In  the  first  and  third  cases  the  temperature  of  the  body  on  which 
the  rays  fall  is  altogether  unaffected,  whereas  in  the  second  it  is  in- 
creased. 

214.  Radiation  in  the  air-pump  vacuum,  may  be 
shown  by  igniting  charcoal,  by  means  of  the  Voltaic 
battery,  placed  in  the  focus  of  a small  mirror  con- 
fined in  the  exhausted  receiver  of  the  air-pump. 

Davy  found  that  the  receiver  being  exhausted  to 
the  effect  upon  the  thermometer  in  the  opposite  focus 
was  nearly  three  times  as  great  as  when  the  air  was 
in  its  natural  state  of  condensation,  Fig.  49,  a is  the 
receiver,  b b the  insulated  wires  connected  with  the 
voltaic  apparatus  igniting  the  charcoal  in  the  focus  of 
the  upper  mirror  c.  In  the  focus  of  the  lower  mirror 
d is  the  thermometer  e. 

215.  The  radiation  of  heat  by  hot  bodies  is  singularly  influenced 
by  the  nature  and  condition  of  their  surfaces,  a circumstance  which 
was  first  examined  by  Leslie.* 

He  made  use  of  a canister  of  planished  block  tin,  forming  a cube  of  six  or 
eight  inches,  having  an  orifice  at  the  middle  of  its  upper  side.  This  orifice  re- 
ceived a cap  having  a small  hole,  through  which  a thermometer  was  inserted,  so 
that  its  bulb  reached  the  centre  of  the  canister.  One  side  of  the  canister  he 
covered  with  black  paint ; destroyed  the  polish  of  another  side,  by  scratching  it 
with  sand-paper  ; tarnished  a third  with  quicksilver ; and  left  the  fourth  bright. 
The  vessel  was  filled  with  boiling  water.  The  radiation  of  caloric  from  the 
blackened  side  was  so  much  more  abundant  than  from  the  others,  as  to  be  even 
sensible  to  the  hand.  He  placed  it  before  a reflector  (Fig.  51)  in  lieu  of  the  heat- 
ed iron  ball  described  (220.)  The  thermometer,  in  the  focus  of  the  second  re- 
flector, indicated  the  highest  temperature,  or  most  copious  radiation  of  caloric, 
when  the  blackened  side  was  presented  to  the  reflector  ; less,  when  the  tarnish- 
ed or  scratched  side  was  turned  towards  it ; and  least  of  all  from  the  polished 
side.t 

* Essay  on  Heat,  1804. 

t The  annexed  figure  represents  an  ingenious  and  much  better  apparatus  for  show- 
ing the  different  absorbing  and  radiating  powers  of  different  surfaces.  A prism  of 
any  convenient  number  of  sides,  is  made  into  an  air  thermometer,  by  placing  a glass 
tube  in  it  through  a conical  opening  which  can  be  made  air 
tight ; the  sides  are  variously  coated.  This  is  made  to  fit 
loosely  into  a prism  of  the  same  form,  but  wanting  one  side. 

To  show  the  different  absorbing  powers  of  the  different  sub- 
stances, the  vessels  are  placed  as  in  the  figure,  before  another, 

A,  containing  hot  water,  hot  sand  or  any  other  convenient 
source  of  heat.  If  the  side  of  the  air  thermometer  which  is 
the  worst  absorbent  of  heat  is  exposed  to  the  source  of  heat, 
the  air  within  is  expanded,  and  the  position  of  the  liquid  in 
the  tube  is  marked  by  the  index;  abetter  absorbent  is  ex- 
posed, and  the  liquid  rises  higher  ; a worse  and  it  falls  below 
its  original  level.  The  outer  sheath  protects  the  sides  which 
are  not  intended  to  be  exposed,  from  the  radiation  of  the  ves- 
sel A and  equalizes  the  radiation  from  the  surfaces  not  ex- 
posed. 

To  show  the  radiating  powers  of  the  surfaces,  the  sheath  is  turned  so  that  the  open 
side  is  exposed  to  the  air. — Bache  in  Amer.  Jour,  xxviii.  326. 


Fig.  50. 


Fig.  49. 


67 


Reflection  of  Heat. 

216.  It  follows  from  these  researches  that  velocity  of  radiation  de-  Sect- 
pends  more  on  the  surface  than  the  substance  of  a radiating  body : Inferences, 
that  the  most  imperfect  radiators  are  to  be  sought  among  those  bodies 

which  are  highly  smooth  and  bright,  such  as  polished  gold,  silver, 
tin,  and  brass  ; but  that  these  same  metals  radiate  freely  when  their 
smoothness  and  polish  are  destroyed,  as  by  scratching  their  surfaces 
with  a file,  or  covering  them  with  whiting  or  lampblack.  A metal- 
lic surface  seems  adverse  to  radiation  independently  of  its  smooth- 
ness, since  a highly  polished  piece  of  glass  radiates  far  better  than 
an  equally  polished  metallic  surface.  Scratching  a surface  probably 
favours  radiation  by  multiplying  the  number  of  radiating  points. 

217.  Some  interesting  experiments  by  Stark  of  Edinburgh  have  stark’* 
appeared,^  illustrative  of  the  connexion  between  radiation  and  the  exPeri* 
colour  of  surfaces.  The  bulb  of  a delicate  thermometer  was  sue- ments‘ 
cessively  surrounded  by  equal  weights  of  differently  coloured  wool, 

was  placed  in  a glass  tube,  heated  by  immersion  in  hot  water  to 
180°,  and  then  cooled  to  50°  in  cold  water.  The  times  of  cooling 
were  21  minutes  with  black  wool,  28  with  red  wool,  and  27  with, 
white  wool.  Concurring  results  were  obtained  with  flour  of  differ- 
ent colours.  Likewise,  black  wool  was  found  to  collect  more  dew 
than  an  equal  weight  of  white  wool,  other  circumstances  being  alike. 

This  is  the  first  time  that  direct  experiments,  seemingly  unexception- 
able, have  been  made  in  proof  of  the  influence  of  colour  over  radia- 
tion. 

218.  It  has  been  known  for  ages  that  the  heat  contained  in  the  Reflection 
solar  rays  admits  of  being  reflected  by  mirrors,  and  a like  property  °f  caloric, 
has  long  since  been  recognized  in  the  rays  emitted  by  red-hot  bo- 
dies; but  that  heat  emanates  in  invisible  rays,  which  are  subject  to 

the  same  laws  of  reflection  as  those  that  are  accompanied  by  light, 
is  a modern  discovery,  noticed  indeed  by  Lambert,  but  first  decisive- 
ly established  by  Saussure  and  Pictet  of  Geneva.  (220) 

This  reflection  of  heat  may  be  shown  by  standing  at  the  side  of  a 
fire  in  such  a position  that  the  heat  cannot  reach  the  face  directly, 
and  then  placing  a plate  of  tinned  iron  opposite  the  grate,  and  at  such 
an  inclination  as  permits  the  observer  to  see  in  it  the  reflection  of 
the  fire:  as  soon  as  it  is  brought  to  this  inclination,  a distinct  im- 
pression of  heat  will  be  perceived  upon  the  face.  If  a line  be  drawn 
from  a radiating  substance  to  the  point  of  a plane  surface  by  which 
its  rays  are  reflected,  and  a second  line  from  that  point  to  the  spot 
where  its  heating  power  is  exerted,  the  angles  which  these  lines  form 
with  a line  perpendicular  to  the  reflecting  plane  are  called  the  angles 
of  incidence  and  reflection , and  are  invariably  equal  to  each  other. 

It  follows  from  this  law,  that  when  a heated  body  is  placed  in  the 
focus  of  a concave  parabolic  reflector,  the  diverging  rays  which  strike 
upon  it  assume  a parallel  direction  with  respect  to  each  other  ; and 
that  when  these  parallel  rays  impinge  upon  a second  concave  reflec- 
tor, standing  opposite  to  the  former,  they  are  made  to  converge,  so  as 
to  meet  together  in  its  focus.  Their  united  influence  is  thus  brought 
to  bear  upon  a single  point. 


* Edin.  Phil.  Trans.  Part  II.  1833. 


68 


Caloric. 


Chap.  I. 


Pictet’s  ex- 
periments. 


Apparent 
reflection  of 
cold. 


219.  Those  surfaces,  that  reflect  light  most  perfectly  are  not  equal- 
ly adapted  to  the  reflection  of  caloric.  Thus,  a glass  mirror,  whicl 
reflects  light  with  great  effect  when  held  before  a blazing  fire,  scarce 
ly  returns  any  heat,  and  the  mirror  itself  becomes  warm.  On  th* 
contrary,  a polished  plate  of  tin,  or  a silver  spoOn,  when  similarly 
placed  reflects,  to  the  hand,  a very  sensible  degree  of  warmth ; anc 
the  metal  itself  remains  cool.  Metals,  therefore,  are  much  bettei 
reflectors  of  caloric  than  glass  ; and  they  possess  this  property,  ex* 
actly  according  to  their  degree  of  polish. 

220.  Caloric  is  reflected  according  to  the  same  law  that  regulate* 
the  reflection  of  light.  This  is  proved  by  an  interesting  experimen 
of  Pictet ; the  means  of  repeating  which  may  be  attained  at  a moder 
ate  expense. 

Provide  two  reflectors  of  planished  tin,  (a  and  6,  Fig.  51),  which  may  be  1« 
inches  diameter,  and  segments  of  a sphere  of  nine  inches  radius.  Parabolic 
mirrors  are  still  better  adapted  to  the  purpose,  but  their  construction  is  less  easy. 
Each  of  these  must  be  furnished,  on  its  convex  side,  with  the  means  of  support- 
ing it  in  a perpendicular  position  on  a proper  stand.  Place  the  mirrors  opposite 
to  each  other  on  a table,  at  the  distance  of  from  6 to  12  feet.  Or  they  may  be 
placed  in  a horizontal  position,  as  represented  in  the  fourth  plate  to  Davy’s 
Chemical  Philosophy , an  arrangement  in  some  respects  more  convenient,  in 

Fig.  51. 


the  focus  of  one,  let  the  ball  of  an  air  thermometer,  or  (which  is  still  better)  one 
of  the  balls  of  a differential  thermometer,  be  situated ; and  in  that  of  the  other, 
suspend  a ball  of  iron,  about  four  ounces  in  weight,  and  heated  below  ignition, 
or  a small  matrass  of  hot  water  ; having  previously  interposed  a screen  before 
the  thermometer.  Immediately  on  withdrawing  the  screen,  the  depression  of 
the  column  of  liquid,  in  the  air  thermometer,  evinces  an  increase  of  tempera- 
ture in  the  instrument. 

In  this  experiment,  the  caloric  flows  first  from  the  heated  ball  to 
the  nearest  reflector  ; from  this  it  is  transmitted,  in  parallel  rays,  to 
the  surface  of  the  second  reflector,  by  which  it  is  collected  into  a fo- 
cus On  the  instrument.  This  is  precisely  the  course  that  is  followed 
by  radiant  light ; for  if  the  flame  of  a taper  be  substituted  for  the 
iron  ball,  the  image  of  the  candle  will  appear  precisely  on  that  spot, 
(a  sheet  of  paper  being  presented  for  its  reception,)  where  the  rays 
of  caloric  were  before  concentrated. 

221.  When  a glass  vessel,  filled  with  ice  or  snow,  is  substituted 
for  the  heated  ball,  the  course  of  the  coloured  liquid  in  the  ther- 
mometer will  be  precisely  in  the  opposite  direction  ; for  its  ascent 
will  show,  that  the  air  in  the  ball  is  cooled  by  this  arrangement. 
This  experiment,  which  appears,  at  first  view,  to  indicate  the  reflec- 


69 


Influence  of  Colours . 

lion  of  cold,  presents,  in  fact,  only  the  reflection  of  heat  in  an  op-  s,ect- In- 
posite  direction ; the  ball  of  the  thermometer  being,  in  this  instance, 
the  hotter  body. 

222.  From  what  has  been  said  concerning  the  communication  Practical 
and  radiation  of  heat,  and  of  the  circumstances  that  influence  the  useSi 
heating  and  cooling  of  bodies  in  these  different  ways,  many  useful 
practical  observations  may  be  drawn.  Water  continues  much  longer 
warm  in  a resplendent  than  in  a blackened  vessel.  Hence  metallic 

ones.,  with  their  surfaces  polished,  are  employed  for  holding  warm 
water,  when  we  wish  it  to  retain  its  heat  for  some  time.  It  is  a 
common  remark,  that  tea  is  more  easily  infused  in  a silver  than  in 
an  earthen  tea-pot,  which  was  at  one  time  supposed  to  be  owing  to 
some  property  of  the  metal  itself,  but  which  is  now  accounted  for  by 
the  laws  of  radiation,  the  bright  metallic  surface  giving  forth  fewer 
rays  than  the  other,  and,  of  course,  cooling  the  water  less  slowly. 

A metal  is,  however,  a good  conductor  $ it  is  of  advantage  therefore, 
to'  have  not  only  a bad  radiator,  but  also  a bad  conductor,  that  the 
heat  given  off  from  the  surface  by  radiation,  may  be  slowly  sup- 
plied from  the  interior.  Hence  the  frequent  use  of  earthen  ware 
covered  with  metallic  matter,  for  holding  warm  fluids,  as  for  jugs 
and  tea-pots,  the  earthen  ware  being  a bad  conductor,  and,  by  hav- 
ing its  surface  resplendent,  becoming  also  a bad  radiator,  by  which 
little  heat  is  given  off. 

223.  When,  on  the  contrary,  we  wish  to  cool  a fluid  quickly, it  must 
be  put  into  a vessel  which  is  a good  conductor,  as  a metallic  one,  and 
with  its  surface  blackened, to  make  it  a good  radiator.  In  conveying 
heated  air,  or  steam,  from  one  place  to  another,  with  the  view  of 
heating  apartments,  the  tube  ought  to  be  made  of  bright  metal,  as 
tinned  iron,  that  there  may  be  little  heat  lost  before  the  air  reaches 
the  place  to  be  warmed.  When,  on  the  contrary,  the  steam  is  to  be 
condensed,  the  tubes  ought  to  be  made  of  blackened  metal,  as  sheet 
iron,  so  that  a great  deal  of  caloric  may  be  given  off,  both  by  radia- 
tion and  by  communication. 

224.  When  we  have  to  guard  a body  from  heat,  we  cannot  employ 
a better  protector  than  a plate  of  bright  metal.  Thus,  in  erecting  a 
stove  near  woodwork,  the  latter  ought  to  have  a sheet  of  tinned  iron 
placed  near  it,  but  not  in  contact  with  it,  by  which  the  greater  part  of 
the  rays  sent  off  from  the  stove  are  reflected.  Should  the  metal  it- 
self become  warm,  the  layer  of  air  between  it  and  the  wood,  being  a 
tery  bad  conductor,  prevents  in  a great  measure  the  transmission  of 
the  heat.  Should  stone  be  employed  as  the  protector,  it  should  be 
whitened,  so  that  it  may  absorb  as  few  of  the  rays  as  possible. 

225.  As  the  reflecting  power  is  materially  influenced  by  the  na- 
ture of  surfaces,  the  absorptive  power  must  be  so  likewise.  Those 
qualities  of  a surface  which  increase  reflection  are  to  the  same  extent 
adverse  to  absorption ; and  those  which  favour  absorption  are  pro- 
portionally injurious  to  reflection.*  Colour  has  considerable  influ- influence  of 
ence,  as  is  shown  by  the  following  very  simple  experiment  ofcol°ur. 
Franklin. 

On  a winter’s  day,  when  the  ground  is  covered  with  snow,  take  four  pieces  of  Exp. 
woollen  cloth,  of  equal  dimensions,  but  of  different  colours,  viz.  black,  blue, 


* See  Ritchie’s  experiments,  Jour.  Roy.  Inst,  v,  305. 


70 


Caloric. 


Chap.  I.  brown,  and  white,  and  lay  them  on  the  surface  of  the  snow,  in  the  immediate 
neighbourhood  of  each  other.  In  a few  hours,  the  black  cloth  will  have  sunk 
considerably  below  the  surface  ; the  blue  almost  as  much  ; the  brown  evidently 
less ; and  the  white  will  remain  precisely  in  its  former  situation. 

Thus  it  appears  that  the  sun’s  rays  are  absorbed  by  the  dark  co- 
loured cloth,  and  excite  such  a durable  heat,  as  to  melt  the  snow  un- 
derneath ; but  they  have  less  power  of  penetrating  the  white. 
Hence  the  preference,  generally  given  to  dark  coloured  clothes  du- 
ring the  winter  season,  and  to  light  coloured  ones  in  summer,  appears 
to  be  founded  on  reason. 

^Stark16*  dependence  of  the  absorptive  power  for  simple  heat  on 

° ’ colour  has  not  till  lately  been  noticed.  From  researches  by  Stark,  it 

seems  that  differently  coloured  wools  wound  upon  the  bulb  of  a ther- 
mometer, and  exposed  within  a glass  tube  to  hot  water,  rose  from  50° 
to  170  in  the  following  times, — black  wool  in  4'  30",  dark  green  in 
5',  scarlet  in  5'  30",  white  in  8'. 

Of  Nobili  227.  An  interesting  connexion  has  been  traced  by  Nobili  and  Mel- 
and  Mel-  loni  between  the  absorbing  and  conducting  power  of  surfaces,*  and 
loni‘  their  researches,  if  free  from  fallacy,  justify  the  inference  that  the 
radiating  and  absorbing  powers  of  surfaces  for  simple  heat  are  in  the 
inverse  order  of  their  conducting  powers,  t.  it. 

Transmi*-  228.  Radiant  heat  passes  with  perfect  freedom  through  a vacuum, 
sionof  The  air  and  gaseous  substances  present  but  a feeble  barrier  to  its 
progress;  so  feeble,  indeed,  that  the  degree  of  impediment  which 
they  occasion  has  not  yet  been  appreciated.  Transparent  media  of 
a denser  kind,  on  the  contrary,  such  as  the  diamond,  rock-crystal, 
glass,  and  water,  even  in  thin  strata,  greatly  interfere  with  its  pas- 
sage, and  when  in  moderately  thick  masses  intercept  it  altogether. 
This  last  remark,  however  is  only  applicable  to  simple  heat,  that  is, 
to  heat  unassociated  with  light.  The  solar  rays  pass  readily  through 
the  substance  of  glass,  both  heat  and  light  being  refracted  in  their 
passage,  as  is  shown  by  the  operation  of  a burning-glass  or  lens ; 
and  though  much  of  the  heat  emitted  by  the  flame  of  a lamp,  or  a 
red  hot  ball  of  iron,  is  arrested  by  glass,  many  calorific  rays  are  di- 
rectly transmitted  along  with  the  light.  But  the  result  is  different 
when  the  heated  body  is  not  luminous.  Leslie  denied  that  any  rays 
of  simple  heat  can  pass  by  direct  transmission  through  glass,  and 
Brewster  has  supported  this  opinion  by  an  argument  suggested  by  his 
optical  researches.!  Several  ingenious  experiments  have  been  made 
on  this  subject  by  Ritchie  ; and  it  has  lately  been  examined  by 
Nobili  and  Melloni  with  the  aid  of  their  thermo-multiplier.  Ail 
these  experimenters  concur  in  the  belief  of  direct  transmission.  The 
total  effect  from  this  cause  is,  however,  very  small ; and  with 
screens  of  moderate  thickness  it  is  wholly  imperceptible. 

Heat  polar-  229.  The  recent  experiments  of  Forbesf  have  established  the 
lzed'  polarization  of  heat  under  all  the  circumstances  in  which  light  is 
polarized,  namely,  by  reflection,  transmission,  and  double  refraction. § 
Theories  of  230.  The  tendency  which  all  bodies  evince  to  attain  an  equa- 
radiation.  0f  temperature  by  means  of  radiation,  has  given  rise  to  two  in- 
genious theories,  suggested  respectively  by  Pictet  and  Prevost. 


* An.  de  Chim.  et  dePhys.  xlviii.  198.  t Phil.  Trans.  1816,  p.  106. 

$ laond.  and  Edin . Phil.  Mag.  vi.  134.  § Edin.  new  Philos.  Jour.,  No.  40. 


71 


Light . 

According  to  the  former,  bodies  of  equal  temperature  do  not  radiate  Rect-  1V- 
at  all ; and  when  the  temperature  is  unequal,  the  hotter  give  calo- 
rific rays  to  the  colder  bodies  till  an  equilibrium  is  established,  at 
which  moment  the  radiation  ceases.  Prevost,  on  the  contrary,  con- 
ceived radiation  to  go  on  at  all  times,  and  from  all  substances,  whe- 
ther their  temperature  were  the  same  or  different  from  that  of 
surrounding  objects.^  Consistently  with  this  view,  the  temperature 
of  a body  falls  whenever  it  radiates  more  heat  than  it  absorbs  ; its 
temperature  is  stationary  when  the  quantities  emitted  and  received 
are  equal ; and  it  grows  warm  when  the  absorption  exceeds  the  radi- 
ation. A hot  body  surrounded  by  others  colder  than  itself,  affords 
an  instance  of  the  first  case  ; the  second  happens  when  all  the  sub- 
stances within  the  sphere  of  each  other’s  radiation  have  the  same 
temperature ; and  the  third  occurs  when  a body  is  introduced  into  a 
room  which  is  warmer  than  itself.  Of  these  theories  the  preference 
is  very  generally  accorded  to  the  latter.  Most  of  the  phenomena  of 
radiation,  indeed,  admit  of  a satisfactory  explanation  by  both  ; but,  on 
the  whole,  the  theory  of  Prevost  is  more  generally  applicable,  t.  12. 

231.  The  sources  of  heat  maybe  reduced  to  six.  1.  The  sun.  Sources  of 
2.  Combustion.  3.  Electricity.  4.  The  bodies  of  animals  during  heat, 
life.  5.  Chemical  action.  6.  Mechanical  action.  All  these  means 

of  procuring  a supply  of  heat,  except  the  last,  will  be  more  conve- 
niently considered  in  other  parts  of  the  work.  The  mechanical  me- 
thod of  exciting  heat  is  by  friction  and  percussion. 

232.  Nothing  is  known  of  the  nature  or  cause  of  heat.  It  has  Nature  of 
been  by  some  considered  as  a peculiar  fluid,  to  which  the  term  eat* 
Caloric  has  been  applied ; and  many  phenomena  are  in  favour  of 

the  existence  of  such  a fluid.  By  others,  the  phenomena  above  de- 
scribed have  been  referred  to  a vibratory  motion  of  the  particles  of 
matter,  varying  in  velocity  with  the  perceived  intensity  of  the  heat. 

In  fluids  and  gases  the  particles  are  conceived  to  have  a motion  round 
their  own  axes.  Temperature , therefore,  would  increase  with  the 
velocity  of  the  vibrations  ; and  increase  of  capacity  would  be  produced 
by  the  motion  being  performed  in  greater  space.  The  loss  of  tem- 
perature, during  the  change  of  solids  into  liquids  and  gases,  would 
depend  upon  loss  of  vibratory  motion,  in  consequence  of  the  acquired 
rotatory  motion. 

Upon  the  other  hypothesis,  temperature , is  referred  to  the  quantity 
of  caloric  present;  and  the  loss  of  temperature,  which  happens  when 
bodies  change  their  state,  depends  upon  the  chemical  combination  of 
the  caloric  with  the  solid  in  the  case  of  liquefaction,  and  with  the 
liquid  in  the  case  of  conversion  into  the  aeriform  state,  b. 


Section  IV.  Of  Light. 

233.  The  minute  investigation  of  the  laws  of  light  belongs  to 
Mechanical  Philosophy  ; it  is  however  requisite  that  some  of  them 
should  partially  be  considered  as  bearing  upon  important  questions 
of  chemical  inquiry.  ... 

The  phenomena  of  vision  are  produced  either  by  bodies  inherent-  Vision. 


* Recherches  sur  la  Chaleur. 


72 


Light. 


in  right 
lines. 


Refraction. 


ChaP  *■  ly  luminous,  such  as  the  sun,  the  fixed  stars,  and  incandescent  sul> 
stances;  or  they  are  referable  to  the  reflection  of  light  from  the  sur- 
faces of  bodies. 

Light  234.  The  manner  in  which  the  eye  is  affected  by  luminous  bodies 

transmitted  shows  that  light  is  transmitted  in  right  lines,  and  every  right  line 
drawn  from  a luminous  body  to  the  eye  is  termed  a ray  of  light,  and 
as  a congeries  of  rays  possesses  the  same  properties  as  the  single 
ray,  the  same  abstract  term  is  frequently  employed  to  designate  the 
congeries. 

235.  Newton  first  discovered  that  certain  bodies  exercise  on  light 
a peculiar  attractive  force.  When  a ray  passes  obliquely  from  air 
into  any  transparent  liquid  or  solid  surface,  it  undergoes  at  entrance 
an  angular  flexure,  which  has  been  called  refraction . The  refrac- 
tion is  towards  the  perpendicular  when  the  ray  passes  into  a denser 
medium,  and  from  the  perpendicular  when  it  passes  into  a rarer  me- 
dium. The  medium  in  which  the  rays  of  light  are  caused  to  ap- 
proach nearest  to  the  line  perpendicular  to  its  surface,  is  said  to  have 
the  greatest  refractive  density. 

It  was  found  by  Newton,  that  unctuous,  or  inflammable  bodies  oc* 
casioned  a greater  deviation  in  the  luminous  rays  than  their  attrac- 
tive mass,  or  density  gave  reason  to  expect.  Hence  he  conjectured, 
that  both  diamond  and  water  contained  combustible  matter.  Ob- 
servation has  since  shown  that  oils  and  other  highly  inflamma- 
ble bodies,  such  as  hydrogen,  diamond,  phosphorus,  sulphur,  amber, 
olive  oil  and  camphor,  have  a refractive  power  which  is  from  two  to 
seven  times  greater  than  that  of  incombustible  substances  of  equal 
density. 

236.  The  refractive  power  of  the  same  inflammable  substance  bears 
a proportion  to  its  perfection,  insomuch  that  this  property  may  be  used 


Refractive 
power  of 
inflamma- 
ble bodies, 


May  be 
used  as  a 
test  of  their 
purity, 


that 

that 


oil  of 


genuine 
of  an  inferior 


as  a test  of  its  purity.  Thus  Wollaston  found 
cloves  has  a refractive  power  of  1,535,  while 
quality  did  not  exceed  1,49S. 

The  density  of  bodies  is  not  the  only  circumstance  that  affects 
their  refractive  power ; it  also  depends  on  their  chemical  nature, 
and  from  the  refractive  power  of  bodies  we  may  in  many  cases  infer 
their  chemical  constitution. 

237.  The  refractive  power  of  compounds  is  not  the  mean  deduced 
the meonof ^rom  components;  which,  however,  it  generally  is  in 

that  of  their  mere  mixtures. 

constitu  238.  When  the  rays  of  light  arrive  at  the  surfaces  of  bodies,  a part 
Reflected  anc^  sometimes  nearly  the  whole,  is  thrown  back,  or  reflec - 

e eC  e ted , and  the  more  obliquely  the  light  falls  upon  the  surface,  the 

greater  in  general  is  the  reflected  portion.  In  these  cases  the  angle 
of  reflection  is  always  equal  to  the  angle  of  incidence. 


Depends  on 
the  chemi- 
cal nature 
as  well  as 
density, 

Of  corn- 


light. 


Let  a a represent  pencils  of  light  falling  upon  the 
surface  of  a polished  piece  of  glass  B,  the  perpendicu- 
lar pencil  will  pass  on  in  a straight  line  to  d. 

Of  the  oblique  pencil,  one  portion  will  enter  the 
glass  and  sutler  refraction  towards  the  perpendicu- 
lar as  at  b,  and  re-entering  the  atmosphere,  it  will  bend 
from  the  perpendicular,  and  re-assume  its  former  di- 
rection, as  at  c.  Another  portion  of  the  oblique  pencil 
will  be  reflected  at  an  angle  equal  to  that  of  its  inci- 
dence, as  at  e. 


Fig.  52. 


Polarization . 


73 


239.  When  a ray  of  light  passes  through  an  oblique  angular  crys-  Sect,  iv. 
talline  body,  it  exhibits  peculiar  phenomena;  one  portion  is  refracted 

in  the  ordinary  way ; another  suffers  extraordinary  refraction,  in  a 
plane  parallel  to  the  diagonal  joining  the  two  obtuse  angles  of  t^ieDoublere. 
crystal ; so  that  objects  seen  through  the  crystal  appear  double.  fractjon< 
Transparent  rhomboids  of  carbonate  of  lime,  or  Iceland  crystal,  ex- 
hibit this  phenomenon  of  double  refraction  particularly  distinct. 

If  a ray  of  light,  which  has  thus  suffered  double  refraction,  be  re- 
ceived  by  another  crystal,  placed  parallel  to  the  first,  there  will  beordinary 
no  new  division  of  the  rays  ; but  if  it  be  placed  in  a transverse  di- refraction, 
rection,  that  part  of  the  ray  which  before  suffered  ordinary  refrac- 
tion will  now  undergo  extraordinary  refraction,  and  reciprocally  that 
which  underwent  extraordinary  refraction  now  suffers  ordinary  re- 
fraction. 

If  the  second  crystal  be  turned  gradually  round  in  the  same  plane,  Refracting 
when  it  has  made  a quarter  of  a revolution,  there  will  be  four  di‘P°^^de 
visions  of  the  ray,  and  they  will  be  reduced  to  two  in  the  half  of  the  j)endentup- 
revolution ; so  that  the  refracting  power  appears  to  depend  upon  on  some 
some  relation  of  the  position  of  the  crystalline  particles.  crystalline 

240.  When  light  is  reflected  from  bodies,  it  retains,  under  many  particles, 
circumstances,  its  former  relations  to  the  refractive  power  of  trans- 
parent media  ; but,  in  certain  cases,  at  angles  differing  for  different 
substances,  the  reflected  rays  exhibit  peculiar  properties,  analogous 

to  those  which  have  suffered  extraordinary  refraction.  Thps,  if  the 
flame  of  a taper  reflected  at  an  angle  of  52°  4 5'  from  the  surface  of 
water,  be  viewed  through  a piece  of  double  refracting  spar,  one  of 
the  images'  will  vanish  every  time  that  the  crystal  makes  a quarter 
of  a revolution. 

241.  When  a ray  of  light  is  made  to  fall  upon  a polished  glass  Angje  of 
surface,  at  an  angle  of  incidence  of  35°  25',  the  angle  of  reflection  incidence 
will  be  equal  to  that  of  incidence.  Let  us  suppose  another  plate  of^qua^tothe 
glass  so  placed  that  the  reflected  ray  will  fall  upon  it  at  the  same  fle;:tion> 
angle  of  35°  25';  this  second  plate  may  be  turned  round  its  axis 
without  varying  the  angle  which  it  makes  with  the  ray  that  falls 

upon  it.  A curious  circumstance  is  observed  as  this  second  Curious  in- 
glass is  turned  round.  Suppose  the  two  planes  of  reflection  to  be 
parallel  to  each  other,  in  that  case  the  ray  of  light  is  reflected  from  mission 
the  second  glass  in  the  same  manner  as  from  the  first.  Let  the  sec-  and  reflcc- 
ond  glass  be  now  turned  round  a quadrant  of  a circle,  so  as  to  make  |j,jbt 
the  reflecting  planes  perpendicular  to  each  other  : now,  the  whole  of 
the  ray  will  pass  through  the  second  glass,  and  none  of  it  will  be 
reflected.  Turn  the  second  glass  round  another  quadrant  of  a cir- 
cle, so  as  to  make  the  reflecting  planes  again  parallel,  and  the  ray 
will  again  be  reflected.  When  the  second  glass  Is  turned  round, 
three  quadrants,  the  light  will  be  again  transmitted,  and  none  of  it 
reflected.  Thus,  when  the  reflecting  planes  are  parallel,  the  light  is 
reflected,  but  when  they  are  perpendicular  the  light  is  transmitted. 

This  experiment  proves,  that,  under  certain  circumstances,  light  can 
penetrate  through  glass  when  in  one  position,  but  not  in  another.  PoIanza' 
This  curious  fact  was  first  observed  by  Malus,  who  accounted  for  it 
by  supposing  the  particles  of  light  to  have  assumed  a particular  po- 
sition as  a needle  does  when  under  the  influence  of  a magnet,  and 
10 


tion. 


74 


Light. 


Chap.  I. 


Analysis  of 
light. 


Prismatic 

colours. 


Newton’s 
theory  of 
colours. 


Seebeck’s 

experi- 

ments. 

Melloni’s. 


Influence 
over  the 
chemical 
enemies  of 
bodies. 


hence  he  called  this  property  of  light,  its  Polarization*  It  has 
since  been  studied  with  laborious  diligence  by  Brewster,  and  by 
Arago  and  Biot.t 

242.  That  a sunbeam,  in  passing  through  a dense  medium,  and 
especially  through  a triangular  prism  of  glass,  gives  rise  to  a series 
of  brilliant  tints  similar  to  those  of  the  rainbow’,  was  known  in  the 
earliest  ages,  but  it  required  the  sagacity  of  Newton  to  develop  the 
cause  of  the  phenomenon.  He  inferred,  that  light  consists  of  rays 
differing  from  each  other  in  their  relative  refrangibilities  ; and,  gui- 
ded by  their  colour  considered  their  number  as  seven  : red,  orange, 
yellow,  green,  blue,  indigo,  and  violet. $ If  the  prismatic  colours,  or 
spectrum , be  divided  into  360  equal  parts,  the  red  rays  will  occupy 
45  of  these  parts,  the  orange  27,  the  yellow  48,  the  green  60,  the 
blue  60,  the  indigo  40,  and  the  violet  80.  Of  these  rays  the  red 
being  least  refrangible,  fall  nearest  that  spot  which  they  would  have 
passed  to,  had  they  not  been  refracted ; while  the  violet  rays  being 
most  refrangible,  are  thrown  to  the  greatest  distance  ; the  interme- 
diate rays,  possess  mean  degrees  of  refrangibility. 

243.  These  differently  coloured  rays,  w'hen  collected  into  a focus 
reproduce  white  light.  Upon  these  phenomena  is  founded  the  New- 
tonian theory  of  colours,  which  supposes  them  to  depend  upon  the 
absorption  of  all  rays,  excepting  those  of  the  colour  observed. 

244.  If  a solar  beam  be  refracted  by  a prism,  and  the  coloured 
image  received  upon  a sheet  of  paper  it  will  be  found,  on  moving 
the  hand  gently  through  it,  that  there  is  an  evident  difference  in  the 
healing  power  of  the  rays.  Englefield,  Davy  and  others,  affirmed 
with  Herschel,  that  the  heat  is  greatest  beyond  the  red  ray  ; while 
others  contend  that  it  is  in  the  red  ray  itself.  The  observations  of 
Seebeck^  have  explained  these  contradictory  statements,  by  showing 
that  the  point  of  greatest  heat  varies  with  the  kind  of  prism  employ- 
ed. These  results  have  been  confirmed  by  Melloni,  who  has  suc- 
ceeded with  a prism  of  rock  salt  in  separating  the  spot  of  maximum 
heat  from  the  coloured  part  of  the  spectrum  by  a much  greater  in- 
terval than  had  been  done  previously.  The  facts  that  have  been 
arrived  at,  go  far  to  prove  that  most,  if  not  all,  of  the  heating  pow- 
er ascribed  to  light,  is  due,  not  to  the  absorption  of  luminous  rays, 
but  to  that  of  the  heat  by  which  they  are  accompanied. 

245.  Light  possesses  considerable  influence  over  the  chemical  en- 
ergies of  bodies.  If  a mixture  of  equal  volumes  of  the  gases  called 
chlorine  and  hydrogen  be  exposed  in  a dark  room,  they  slowly  com- 
bine, and  produce  hydrochloric  acid  gas  ; but,  if  exposed  to  the  di- 
rect rays  of  the  sun,  the  combination  is  very  rapid,  and  often  accom- 
panied by  an  explosion. 


* See  Fischer’s  Elements  of  Natural  Philosophy , page  336.  Thomson’s  System 
1.  p.  16. 

t Phil.  Trans.  1813,  1814,  1815,  1816,  1817. — Ann.  dc  Chim.  tom.  94.  Traitt  de 
Phys. 

t Wollaston  found,  however,  that  when  a beam  of  light  only  inrth  of  an  inch  broad 
is  received  by  the  eye,  at  the  distance  of  ten  feet,  through  a clear  prism  of  flint  glass, 
only  four  colours  are  seen,  viz.  red,  yellowish  green,  blue,  and  violet-  Brewster  has 
proved  that  the  colours  of  the  spectrum  are  occasioned  by  threo  simple  primary  rays 
viz.  the  red,  yellow  and  blue. 

§ Edin.  Jour,  of  Sci.  1,  358. 


Photometer. 


lb 


Chlorine  and  carbonic  oxide  have  scarcely  any  tendency  to  com-  Sect,  iv. 
bine,  even  at  high  temperatures,  when  light  is  excluded,  but  exposed 
to  the  solar  rays  they  enter  into  chemical  union.  Chlorine  has  lit- 
tle action  upon  water,  unless  exposed  to  light,  and,  in  that  case,  the 
water,  which  consists  of  oxygen  and  hydrogen,  is  decomposed.  The 
hydrogen  unites  with  the  chlorine  to  produce  hydrochloric  acid,  and 
the  oxygen  is  evolved  in  a gaseous  form. 

246.  These,  and  numerous  other  similar  cases,  show  that  solar  Produces 
light  influences  the  chemical  energies  of  bodies,  independent  of  its 
heating  powers.  Many  important  facts  have  been  ascertained  by  Ritter, 
Wollaston,  and  Davy.  Scheele*  threw  the  prismatic  spectrum  upon 

a sheet  of  paper,  moistened  with  a solution  of  nitrate  of  silver,  a salt 
quickly  decomposed  by  the  agency  of  light.  In  the  blue  and  violet 
rays  the  silver  was  soon  reduced,  producing  a blackness  upon  the 
paper,  but  in  the  red  ray  scarcely  any  similar  effect  was  observed. 
Wollaston  and  Ritter  discovered  that  these  chemical  changes  were 
most  rapidly  effected  in  the  space  which  bounds  the  violet  ray,  and 
which  is  out  of  the  visible  spectrum. 

Davy  has  observed,  that  certain  metallic  oxides,  when  exposed  to 
the  violet  extremity  of  the  prismatic  spectrum,  undergo  a ehange 
similar  to  that  which  would  have  been  produced  by  exposure  to  a 
current  of  hydrogen  ; and  that  when  exposed  to  the  red  rays,  they 
acquire  a tendency  to  absorb  oxygen. t 

247.  The  more  refrangible  rays  of  light  have  been  thought  to  Magnet- 
possess  the  property  of  rendering  steel  or  iron  magnetic.  This  pro- iz*n&  a.vs- 
perty  was  announced  by  Morrichini  of  Rome;  but  as  the  experiment 

did  not  succeed  in  other  hands,  the  subject  was  involved  in  some  de- 
gree of  uncertainty.  The  fact,  however,  appeared  to  be  established 
by  Mrs  Somerville  of  London,  in  1826,  who  gave  an  account  of  her 
researches  to  the  Royal  Society.  Since  that  period  the  subject  has 
been  re-examined  by  Riess  and  Moser.  They  object  to  Mrs  Somer- 
ville’s results,  that  her  method  of  ascertaining  the  magnetic  state  of 
the  needles  used  in  the  experiments,  was  not  sufficiently  precise  : 
they  deny  the  supposed  magnetizing  power  of  light. 4 

248.  The  comparative  intensities  of  light  are  measured  by  the  in-  photome- 
slrument  called  a Photometer : that  which  is  known  as  Leslie’s  is  ter- 
constructed  on  the  principle  that  light,  in  proportion  to  its  absorption, 
produces  heat.  It  is  merely  a very  delicate  and  small  differential 
thermometer,  enclosed  in  a thin  and  pellucid  glass  tube.  One  of  the 

bulbs  is  of  black  glass,  which,  when  the  instrument  is  suddenly  ex- 
posed to  light,  becoming  warmer  than  the  clear  bulb,  indicates  the 
effect  by  the  depression  of  the  fluids  From  the  experiments  of 
Turner  and  Christison  this  instrument  does  not  appear  applicable  to 
lights  which  differ  in  colour,  because  the  relation  between  the  heat- 
ing and  illuminating  power  of  such  light  is  exceedingly  variable. 

Thus,  the  light  emitted  by  burning  cinders  or  red-hot  iron,  even  after 
passing  through  glass,  contains  a quantity  of  calorific  rays,  which  is 
out  of  all  proportion  to  the  luminous  ones  ; and,  consequently,  they 
may  and  do  produce  a greater  effect  on  the  photometer,  than  some 

* Experiments  on  Air  and  Fire , p.  78,  &c.  t Elements  of  Chem.  Phil. 

Edin-  Jour,  of  Sci.  2,  225.  § Leslie  on  Heat , p.  424. 


76 


Chap.  I. 


Perfect 
vegetation 
requires 
the  influ- 
ence of 
solar  rays. 


Drum- 

mond’s 

light. 


Phospho- 

rescent 

bodies. 


Solar  phos- 
phori. 


Light. 

lights  whose  illuminating  powers  are  far  stronger.  Leslie  conceived 
that  light  when  absorbed  is  converted  into  heat;  but  according  to 
the  experiments  already  referred  to,  the  effect  must  be  attributed,  not 
so  much  to  the  light  itself,  as  to  the  absorption  of  the  calorific  rays 
by  which  it  is  accompanied.  A differential  thermometer,  containing 
the  vapour  of  ether,  may  also,  in  certain  experiments  be  advanta- 
geously used  as  a Photometric  Thermometer 

249.  In  nature  the  influence  of  the  solar  rays  is  very  complex,  and 
the  growth,  colour,  flavour,  and  even  the  forms  of  many  vegetables, 
are  much  dependent  upon  them.  This  is  seen  in  many  plants  which 
are  protected  from  the  sun’s  rays  : celery  and  endive  are  thus  culti- 
vated with  the  view  of  rendering  them  palatable  ;t  and  plants  which 
are  made  to  grow  in  a room  imperfectly  illuminated,  always  bend 
towards  the  apertures  by  which  the  sun’s  rays  enter.  The  changes 
too  which  vegetables  effect  upon  the  circumambient  atmosphere  are 
influenced  by  the  same  cause. 

250.  In  the  animal  creation,  brilliancy  of  colour  and  gaudy  plu- 
mage belong  to  the  tropical  climates  ; more  sombrous  tints  distin- 
guish the  polar  inhabitants  ; and  dull  colours  characterize  nocturnal 
animals,  and  those  who  chiefly  abide  below  the  surface. 

251.  When  bodies  are  rendered  luminous  by  elevation  of  tem- 
perature, the  light  which  they  emit  often  appears  dependent  upon  the 
heat  to  which  they  are  subjected,  and  the  common  terms  red-hot  and 
white-hot  are  used  to  designate  those  appearances.  There  are,  how- 
ever, certain  bodies,  which,  at  high  temperatures,  are  remarkable 
for  the  quantity  and  extreme  brilliancy  of  their  light,  independent  of 
actual  combustion  ; this  is  the  case  with  several  of  the  earths,  but 
more  especially  with  lime,  a small  ball  of  which,  £ inch  in  diameter, 
being  ignited  in  the  flame  of  alcohol  urged  by  oxygen  gas,  emits 
light,  having  about  thirtyseven  times  the  intensity  of  an  Argand’s 
lamp  burner. $ 

252.  There  are  many  substances  which,  when  heated  to  a certain 
point,  become  luminous  without  undergoing  combustion,  and  such 
bodies  are  said  to  be  phosphorescent.  The  temperatures  which  they  re- 
quire for  this  purpose  are  various  ; it  generally  commences  at  about 
400°,  and  may  be  said  to  terminate  at  the  lowest  visible  redness.  Some 
varieties  of  phosphate  of  lime,  of  fluor  spar,  of  bituminous  carbonate 
of  lime,  of  marble,  and  sand,  and  certain  salts,  are  the  most  remarka- 
ble bodies  of  this  description. § Their  luminous  property  may  be 
best  exhibited  by  scattering  them  in  coarse  powder  upon  an  iron 
plate  heated  nearly  to  redness.  Oil,  wax,  spermaceti,  and  butter, 
when  yearly  boiling,  are  also  luminous. 

253.  Another  class  of  phosphorescent  bodies  has  been  termed 


* Brande,  Phil.  Trans.  1820.  A photometer  has  been  described  by  Ritchie,  in  the 
Quart.  Jour.  vol.  19,  p.  299.  For  a description  of  Rumfont’s  Photometer,  see  Phil. 
Trans,  vol.  84.  It  determines  the  comparative  strength  of  lights  by  a comparison  of 
their  shadows.  ^ 

+ The  process  is  termed  etiolation , or  blanching, 

X Drummond,  in  Phil.  Trans.  1826.  See  figure  and  description  of  his  apparatus 
in  Brewster’s  Edin.  Jour,  of  Sci.  v. 

§ Wedgewood,  Phil.  Trans,  vol.  82. 


Light  of  Flames . 


77 


solar  phosphor i,  from  becoming-  luminous  when  removed  into  a dark  ...-Sect' 1 _ 
room  after  having  been  exposed  to  the  sunshine.^  Of  this  descrip- 
tion are  Canton’s,  Baldwin’s,  and  the  Bolognian  phosphorus.! 

254.  A third  set  of  bodies,  belonging  to  this  class,  are  those  which  Spontane- 
are  spontaneously  phosphorescent.  Such  are,  especially,  the  flesh  of  oas  Phos’ 
salt-water  fish  just  before  it  putrefies,  and  decayed  wood.  Thejg^gf" 
glow-worm  and  the  lantern-fly  are  also  luminous  when  alive  ; and 

the  hundred  legged  worm,  and  some  others,  shine  brilliantly  when 
irritated.!  (See  Bost.  Jour.  2,  101.) 

255.  Percussion  and  friction  are  often  attended  by  the  evolution  of  Light  from 
light,  as  when  flint  pebbles,  pieces  of  sugar,  and  other  substances,  are  percussion 
struck  or  rubbed  together.  The  crystallization  of  some  substances, or  friction* * * § 
as  benzoic  acid,  and  acetate  of  potassa  has  been  found  to  be  attended 

with  similar  phenomena. § 

256.  From  experiments  in  which  air  has  been  intensely  heated,  it  Airin- 
has  been  concluded  that  gaseous  matter  is  incapable  of  becoming  ]u-caPat>le  of 
minous;  for,  though  the  temperature  of  air  be  such  as  to  render  lumincmsl 
solid  bodies  white-hot,  it  does  not  itself  become  visible.il  Flame, 
however,  may,  in  general,  be  regarded  as  luminous  gaseous  matter. 
Hydrogen  gas,  probably,  furnishes  the  purest  form  of  flame  which 

can  be  exhibited;  for  the  flames  of  bodies  which  emit  much  light, 
derive  that  power  from  solid  matter  which  is  intensely  ignited  and 
diffused  through  them,  and  which,  in  ordinary  flames,  as  of  gas, 
tallow,  wax,  oil,  &c.  consists  of  finely  divided  charcoal. 

257.  The  intensity  of  the  heat  of  flames  which  are  but  little  lurni-  Lio-ht  and 
nous,  as  of  hydrogen  gas,  spirit  of  wine,  &c.  maybe  shown  by  tempera- 
introducing  into  them  some  fine  platinum  wire,  which  is  instantly 
rendered  white-hot  in  those  parts  where  the  combustion  is  most  per- 
fect. It  is  even  intensely  ignited  in  the  current  of  air  above  the 


* For  practical  directions  for  observing  the  phosphorescence  of  bodies,  see  Faraday’s 
Chemical  Manipulation. 

t Cantonas  phosphorus  is  prepared  thus  : — Calcine  oyster-shells  in  the  open  fire  for 
half  an  hour,  then  select  the  whitest  and  largest  pieces  and  mix  them  with  one  third  pound^*  c°m 
their  weight  of  flowers  of  sulphur,  pack  the  mixture  closely  into  a covered  crucible,  ' 
and  heat  it  t.o  redness  for  an  hour.  When  the  whole  has  cooled,  select  the  whitest  pieces 
for  use.* 

Baldwin’s  phosphorus  is  prepared  by  heating  nitrate  of  lime  to  a dull  red  heat,  so  as  7 

to  form  it  into  a compact  mass : and  the  Bolognian  phosphorus,  discovered  by  Vincen-  thg  Bosnian 
zio  Cascariolo,  a shoemaker  of  Bologna,  is  made  by  reducing  compact  sulphate  of  ha-  phosphorus, 
ryta  to  a fine  powder,  which  is  formed  into  cakes  with  mucilage,  and  these  are 
heated  to  redness. t 

Wilson  has  also  made  a variety  of  curious  experiments  on  solar  phosphori ; and  he 
has  discovered  the  simplest  and  most  effectual  of  these  bodies,  which  may  be  obtained  Wi!sor^“scX' 
by  closely  observing  the  following  directions ; — Take  the  most  flaming  coals  off  a brisk  pennnen  s- 
fire,  and  throw  in  some  thick  oyster  shells  ; then  replace  the  coals,  and  calcine  them 
for  an  hour ; remove  them  carefully,  and,  when  cold,  it  will  be  found  that  after  expos- 
ing them  for  a few  minutes  to  the  light,  they  will  glow  in  the  dark,  with  most  of  the 
prismatic  colours.? 

t It  appears  from  the  experiments  of  Canton  and  of  Hulme,§  that  sea-fish  become 
luminous  in  about  twelve  hours  after  death,  that  it  increases  till  putrefaction  is  evident, 
and  then  it  decreases.  Immersion  in  sea-water  does  not  affect  this  luminous  matter  ; 
on  the  contrary,  the  brine  is  itself  rendered  luminous  ; but  it  is  extinguished  by  pure 
water,  and  by  a variety  of  substances  which  act  chemically  upon  the  animal  matter. 

§ Brewster’s  Journal , 3,  368.  ||  Wedgewood,  Phil.  Trans.  17  92. 

* Phil.  Trans.  Vol.  58.  f Aikin’s  Diet.  art.  Phosphori.  | Wilson  on  Phosphori,  p.  20. 

§ Phil.  Trans.  Vols.  lix.  xc.  and  xci. 


78 


Light. 


Chap.  I. 


Exp. 


Exp. 


Exp. 


Eff  ct  nf 
wire  gauze 
on  flame. 


Davy’s 
S’  -tv 

lamp. 


Theory  of 
phospho- 
rescence 
ami  incan 
descence. 


flame,  as  may  be  shown  by  holding  a piece  of  platinum  wire  over 
the  chimney  of  an  Argand  lamp  fed  with  spirit  of  wine;  the  high 
temperature  of  this  current  is  also  exhibited  by  the  common  expedi- 
ent of  lighting  paper  by  holding  it  in  the  heated  air  which  rushes 
out  of  a common  lamp-glass. 

The  high  temperature  of  flame  is  further  proved  by  certain  cases 
of  combustion  without  flame.  Thus,  if  a heated  wire  of  platinum  be 
introduced  into  any  inflammable  or  explosive  mixture,  Fig.  53. 
it  will  become  ignited , and  continue  so  till  the  gas  is 
consumed ; but  inflammation  will,  in  most  cases,  only 
take  place  when  the  wire  becomes  while-hot. 

This  experiment  is  easily  made  by  pouring  a small  quantity 
of  ethor  into  the  bottom  of  a deep  wine-glass,  or,  what  is  better, 
a glass  vessel,  like  that  represented  in  Fig  53,  and  suspending  in 
it  a coil  of  heated  platinum  wire  so  as  to  be  a little  above  the 
surface  of  the  ether ; the  wire  becomes  red  hot,  but  does  not 
inflame  the  vapour  of  the  ether  till  it  acquires  an  intense  white 
heat. 

The  same  fact  is  exhibited  by  putting  a small  coil  of  fine  platinum 
wire  round  the  wick  of  a spirit  lamp,  (Fig.  54,)  which,  when 
heated,  becomes  red  hot,  and  continues  so,  as  long  as  the  vapour 
of  the  spirit  is  supplied,  the  heat  never  becoming  sufficiently  in- 
tense to  produce  its  inflammation. 

25S.  Such  being  the  nature  of  flame,  it  is  obvi- 
ous, that  if  we  cool  it  by  any  means,  we  must  at  the  

same  time  extinguish  it.  This  may  be  effected  by  causing  it  to  pass 
through  fine  wire  gauze,  which  is  an  excellent  conductor  and  radia- 
tor of  heat,  and  consequently  possessed  of  great  cooling  power. 

If  a piece  of  fine  brass  or  iron  wire-gauze  be  brought  down  upon  the  flame  of  a 
candle,  or  what  answers  better,  upon  an  inflamed  jet  of  oil  gas,  it  will,  as  it 
were,  cut  the  flame  in  half.  That  the  cool  gaseous  matter  passes  through,  may 
be  shown  by  again  lighting  it  upon  the  upper  surfac?. 

The  power,  therefore,  of  a metallic  tissue  thus  to  extinguish 
flame,  will  depend  upon  the  heat  required  to  produce  the  combustion, 
as  compared  with  that  acquired  by  the  tissue  ; and  the  flame  of  the 
most  inflammable  substances,  and  of  those  that  produce  most  heat  in 
combustion,  will  pass  through  a metallic  tissue  that  will  interrupt  the 
flame  of  less  inflammable  substances,  or  those  that  produce  little  heat 
in  combustion  ; so  that  different  flames  will  pass  through  at  different 
degrees  of  temperature. 

259.  The  discovery  of  these  facts,  respecting  the  nature  and  prop- 
erties of  flame,  led  Davy  to  apply  them  to  the  construction  of  the 
Miners'  safety  lamp , which  will  be  explained  under  the  article  Light 
Carburetted  hydrogen  gas. 

260.  The  phenomena  exhibited  by  phosphorescent  and  incandes- 
cenf  bodies,  and  in  the  process  of  combustion,  have  sometimes  been 
explained  upon  the  idea  that  the  light  and  heat  evolved  were  pre- 
viously in  combination  with  the  substances,  and  that  they  are  after- 
wards merely  emitted,  in  consequence  of  decomposition;  and  that 
the  solar  phosphori  absorb  light  and  again  give  it  out  unchanged; 
but  the  fact,  that  the  colour  of  the  light  emitted  is  more  dependent 
on  the  nature  of  the  phosphorescent  body  than  on  the  colour  of  the 
light  to  which  it  was  exposed,  seems  inconsistent  with  this  explana- 


Electricity.  79 

lion.  Chemical  action  is  not  connected  with  the  phenomena  ; for  Sect,  v. 
the  phosphori  shine  in  vacuo , and  in  gases  which  do  not  act  on  them, 
and  some  even  under  water.^ 


Section  V.  Electricity. 

261.  The  term  electricity  is  derived  from  the  Greek  word  ehexjQov,  Electrical 
amber , on  account  of  the  property  which  this  substance  was  known  excitement, 
to  possess  of  attracting  light  substances  when  rubbed.  If  a piece  of 
sealing-wax  and  of  dry  warm  flannel  be  rubbed  against  each  other, 

they  both  become  capable  of  attracting  and  repelling  light  bodies. 

A dry  and  warm  sheet  of  paper,  rubbed  with  India  rubber,  or  wool- 
len, or  a tube  of  glass  rubbed  upon  silk,  exhibit  the  same  phenomena. 

In  these  cases  the  bodies  are  said  to  be  electrically  excited ; and 
when  in  a dark  room,  they  appear  luminous. 

262.  If  two  pith-balls  be  electrified  by  touching  them  with  the  Repulsion 
sealing-wax  or  with  the  flannel,  they  repel  each  other;  but  if  one  and  attrac_ 
pith-ball  be  electrified  by  the  wax,  and  the  other  by  the  flannel,  they  10n’ 
attract  each  other.  The  same  applies  to  the  glass  and  silk. 

If  one  ball  be  electrified  by  sealing-wax  rubbed  by  flannel,  and 
another  by  silk  rubbed  with  glass,  those  balls  will  repel  each  other. 

But  if  one  ball  be  electrified  by  the  sealing-wax  and  the  other  by  the 
glass,  they  then  attract  each  other.! 

263.  The  terms  vitreous  and  resinous  electricity  were  applied  to  Dufay’s 
these  two  phenomena.  According  to  Dufay  the  vitreous  and  resi-  theory, 
nous  electricities  are  distinct;  an  unexcited  body  contains  both  in  a 

state  of  combination  or  neutralization,  and  cannot,  therefore,  exhibit 
any  electrical  attractions  or  repulsions.  But  friction  disturbs  this 
combination,  or  electric  equilibrium,  causing  the  vitreous  electricity 
to  accumulate  in  one  body  and  the  resinous  in  the  other.  They  are 
both  consequently  in  an  excited  state,  and  continue  to  be  so  till  each 
recovers  that  kind  of  electricity  which  it  had  lost. 

A different  explanation  yvas  proposed  by  Franklin,  which  is  found-  Franklin’* 
ed  on  the  supposition  that  there  is  only  one  kind  of  electricity.  tbeorJr- 
When  bodies  contain  their  natural  quantity  of  electricity,  they  do 
not  manifest  any  electrical  phenomena  ; but  they  are  excited  either 
by  an  increase  or  diminution  in  that  quantity.  Thus  on  rubbing  a 
piece  of  glass  with  a woollen  cloth,  the  electrical  condition  of  both 
substances  is  disturbed ; the  former  acquires  more,  the  other  less 
than  its  natural  quantity.  These  different  states  were  expressed  by 
the  terms  plus  and  minus,  or  positive  and  negative,  the  first  corres- 
ponding to  the  vitreous,  the  second  to  the  resinous  electricity  of 
Dufay.! 


* See  Davy’s  Elements  1,213,  &c. — Murray’s  System  1,  570— Ure’s  Did.  article 
Caloric — Hare  in  Amer.  Jour.  iv.  12,  &c. — Turner’s  Elements,  69. 

f These  experiments  are  conveniently  performed  with  a large  downy  feather  sus- 
pended by  a dry  thread  of  white  silk. 

t As  writers  on  chemistry  continue  to  use  the  terms  positive  and  negative , they  are 
here  retained. 


80 


Chap.  I. 

Electrome- 

ter. 


Method  of 
determin- 
ing the 
kind  of 
electricity. 


Conductors 
and  non- 
conductors. 


Electricity 
passes 
through 
rarefied  air 
or  a vacu- 
um. 

No  con- 
stant rela- 
tion be- 
tween the 
state  of 
bodies  and 
their  con- 
ducting 
powers. 


Some  sub- 
stances be- 
come elec- 
tric by  heat. 

Phenomena 
observed  in 
using  elec- 
trical ma- 
chines. 


Electricity. 

264.  Very  delicate  pith-balls,  or  strips  of  gold  leaf,  are 
usually  employed  in  ascertaining  the  presence  of  electricity; 
and,  by  the  way  in  which  their  divergence  is  affected  by  glass 
or  sealing-wax,  the  kind  or  state  of  electricity  is  judged  of. 

When  properly  suspended  or  mounted  for  delicate  experi- 
ments, they  form  an  electrometer  or  electroscope.  (Fig.  55.) 

For  this  purpose  the  slips  of  gold  leaf  are  suspended  by  a 
brass  cap  and  wire  in  a glass  cylinder  ; they  hang  in  contact 
when  un-electrified;  but  when  electrified  they  diverge.* 

265.  The  kind  of  electricity  by  which  the  gold  leaves  are  diverged 
may  be  judged  of  by  approaching  the  cap  of  the  instrument  with  a 
stick  of  excited  sealing-wax  ; if  it  be  negative  the  divergence  will 
increase  ; if  positive , the  leaves  will  collapse,  upon  the  principle  of 
the  mutual  annihilation  of  the  opposite  electricities,  or  that  bodies 
similarly  electrified  repel  each  other,  but  that  when  dissimilarly 
electrified  they  become  mutually  attractive. 

266.  Some  bodies  suffer  electricity  to  pass  readily  along  their  sur- 
faces, and  are  called  conductors.  Others  only  receive  it  upon  the 
spot  touched,  and  are  called  imperfect  or  non-conductors.  They  are 
also  called  insulators.]  The  metals  are  all  conductors  ;t  dry  air, 
glass,  sulphur,  and  resins,  are  non  conductors.  Water,  damp  wood, 
spirit  of  wine,  damp  air,  and  some  oils  are  imperfect  conductors. 

Rarefied  air  admits  of  the  passage  of  electricity  ; so  does  the 
Torricellian  vacuum. 

267.  There  appears  to  be  no  constant  relation  between  the  state 
of  bodies  and  their  conducting  powers  ; among  solids,  metals  are 
conductors,  but  gums  and  resins  are  non-conductors;  among  liquids, 
strong  alkaline,  acid,  and  saline  solutions,  are  good  conductors ; 
pure  water  is  an  imperfect  conductor,  and  oils  are  non-conductors ; 
wax  and  many  other  solids  are  imperfect  conductors,  but  when  fused 
are  good  ones.  Conducting  powers  belong  to  bodies  in  the  most  op- 
posite states ; thus  the  flame  of  alcohol,  and  ice,  are  equally  good 
conductors.^  Glass  is  a non-conductor  when  cold,  but  conducts  when 
red-hot;  the  diamond  is  a non-conductor,  but  pure  and  well  burned 
charcoal  is  among  the  best  conductors. 

268.  There  are  many  mineral  substances  which  show  signs  of 
electricity  when  heated,  as  the  tourmalin,  topaz,  diamond,  boracite, 
&c.  ; and  in  these  bodies  the  different  surfaces  exhibit  different  elec- 
trical states. II 

269.  When  an  electrical  machine  is  in  good  order,  and  the  at- 
mospbtre  dry,  it  produces  a crackling  noise  when  the  plate  or  cylin- 
der is  turned,  and  flashes  or  sparks  of  light  are  seen  upon  various 


* For  other  forms  see  Turner’s  Chem.  81. 

t The  insulation  of  substances  is  frequently  required  in  electro-chemical  experi- 
ments ; a plate  of  mica  is  the  best  substance  for  the  purpose,  then  a plate  of  resin  or 
wax,  or  iu  their  absence,  a plate  of  warm  glass.  Faraday. 

t Of  the  metals,  Harris  found  silver  and  copper  to  be  the  best  conductors,  and  after 
these  gold,  zinc,  platinum,  iron,  tin,  lead,  antimony,  and  bismuth — Phil.  Trans.  1827. 
Part  1,21. 

§ Biot,  Traitdde  Physique,  tom.  ii.  p.  213. 

||  For  a description  of  Electrical  machines  and  a more  full  account  of  Electricity, 
see  Cambridge  rial.  Phil.  vol.  2,  Fischer’s  Elements  of  Nat.  Phil.  p.  164.  Brande's 
Chem.  69. 


Fig.  65. 

ia! 


A 


X 


81 


Faraday’s  Views. 


parts  of  the  glass  passing  from  the  cushion  to  the  conductor  ; if  the  sect.  y. 
knuckle  be  held  near  the  conductor,  sparks  pass  to  it  through  some 
inches  of  air,  with  a peculiar  noise,  and  excite  slightly  painful  sen- 
sation in  the  part  upon  which  they  are  received.  It  is  conjectured 
that  the  cause  of  the  light  thus  perceived,  is  the  sudden  compres- 
sion of  the  air  or  medium  through  which  the  electricity  passes,  and  j^t;  an 
it  is  always  probably  attended  by  a proportionate  elevation  of  tem- 
perature, as  is  shown  by  the  power  of  the  spark  to  inflame  spirit  of 
wine,  fulminating  silver,  and  other  easily  inflammable  compounds. 

270.  Another  cause  of  excitement  is  proximity  to  an  electrified 
body,  which  has  a tendency  to  induce  an  electrical  state  opposite  to 
its  own.  Thus  an  excited  stick  of  sealing-wax  attracts  light  bodies 
in  its  vicinity,  and  occasions  them  to  be  positively  electrified.  If  an  Electricity 
insulated  conductor  be  electrified,  and  an  uninsulated  conductor  bebymduc- 
opposed  to  it,  there  being  between  the  two  a thin  stratum  of  air, tlon- 
glass,  or  other  non-conductor,  the  uninsulated  conductor,  under  such 
circumstances,  acquires  an  opposite  electrical  state  to  that  of  the  orig- 
inally electrified  insulated  conductor.  In  this  case,  the  uninsulated 
body  is  electrified  by  induction,  and  the  induced  electricity  remains 
evident,  until  an  explosion,  spark,  or  discharge  happens,  when  the 
opposite  electricities  annihilate  each  other.  Induced  electricity  may 
thus  be  exhibited  through  a long  series  of  insulated  conductors,  pro- 
vided the  last  of  the  series  be  in  communication  with  the  earth. 


j c 


put 


Thus,  in  Fig.  56,  Fig,  56- 

A,  may  represent 
the  positive  conduc- 
tor of  the  electrical 
machine ; b,  c,  and  d. 
three  insulated  con 
ductors,  placed  at  a 

little  distance  from 

each  other,  d , having  a chain  touching  the  ground  ; then  the  balls  1,  being  posi 
tive,  will  attract  the  balls  2,  which  are  rendered  negative  by  induction.  Under 
these  circumstances,  each  of  the  conductors  becomes  polar,  and  the  balls  3 are 
positive,  while  4 are  negative,  5 positive,  6 negative,  &c. ; the  central  points  of 
the  conductors,  bed,  are  neutral.  \\i  hen  these  opposite  electrical  states  have 
arrived  at  a certain  intensity*,  sparks  pass  between  the  different  conductors,  and 
the  electrical  phenomena  cease.  B.  73. 


Illustra- 

tion. 


271.  The  recent  investigations  of  Faraday,!  have  led  him  to  the  Faraday’s 
inference  that  induction  is  essentially  an  action  of  contiguous  parti- views, 
cles,  through  the  intermediation  of  which  the  electric  force,  origi- 
nating or  appearing  at  a certain  place,  is  propagated  to  or  sustained 
at  a distance,  appearing  there  as  a force  of  the  same  kind  exactly 
equal  in  amount,  but  opposite  in  its  directions  and  tendencies.  In- 
duction is  considered  as  the  essential  function,  both  in  the  first  de 
velopment  and  the  consequent  phenomena  of  electricity.  He  con 
ceives  that  induction  consists  in  a certain  polarized  state  of  the  par- 
ticles, into  which  they  are  thrown  by  the  electrified  body  sustaining 
the  action,  the  particles  assuming  positive  and  negative  points  or 


* Electricians  generally  employ  the  term  quantity  to  indicate  the  absolute  quanti- 
ty of  electric  power  in  any  body,  and  the  term  intensity  to  signify  its  power  of  passing 
through  a certain  stratum  of  air  or  other  ill-conducting  medium, 
t P kilos.  Trans.  1838.  p.  1. 

11 


82 


Chap.  I. 


Specific  in- 
ductive ca- 
pacity. 
Faraday’s 
differential 
ind  udome- 
ter. 


Conse- 
quences of 
the  theory. 


Electricity. 

parts,  which  are  symmetrically  arranged  with  respect  to  each  other 
and  the  inducting  surface  or  particles.* 

272.  For  examining  the  specific  inductive  capncity  of  bodies, 
Faraday  has  contrived  an  apparatus,  which  he  calls  a Differential 
Inductometer.  It  consists  of  three  insulated  metallic  plates,  placed 
facing  each  other ; the  centre  one  being  fixed,  and  the  other  two 
moveable  upon  slides,  by  which  they  may  be  approximated  to  or 
withdrawn  from  the  centre.  When  a charge  is  communicated  to 
the  centre  plate  under  ordinary  circumstances,  the  induction  is  equal 
on  both  sides  and  the  gold  leaves  are  not  disturbed.  But  if  after 
uninsulating  them,  and  again  insulating  them,  a thick  plate  of  shel- 
lac or  sulphur,  be  interposed  between  two  of  the  plates,  unequal  in- 
duction will  take  place  on  the  two  sides,  and  the  gold  leaves  will 
attract  each  other.  By  these  means,  Faraday  has  ascertained  that, 


taking  the  specific  inductive  capacity  of  air  to  be  I. 

That  of  Glass  is  1.76 

Shellac  - 2. 

Sulphur  - 2.24 


The  results  obtained  with  spermaceti,  oil  of  turpentine,  and  nap- 
tha, were  higher  than  that  of  air,  but  their  conducting  powers  inter- 
fered with  the  accuracy  of  the  experiments. 

By  another  form  of  apparatus,  he  ascertained  that  all  aeriform 
matter  has  the  same  power  of  sustaining  induction  ; and  that  no  va- 
riations in  the  density  or  elasticity  of  gases  produced  any  variation 
in  their  electric  tension,  until  rarefaction  is  pushed  so  far  as  that  dis- 
charge may  lake  place  across  them. 

No  difference  was  found  with  hot,  cold,  dry  or  damp  air.  These 
experiments  have  established  the  important  discovery  of  the  princi- 
ple of  specific  inductive  capacity. t 

273.  It  is  essential  that  the  student  should  reflect  carefully  on 
the  plain  consequences  of  the  theory  of  electricity,  since  the  appli- 
cations of  this  knowledge  are  numerous.  A few  of  these  may  now 
be  enumerated  — 

1.  An  electrified  body  attracts  light  objects  near  it,  because  it  in- 
duces in  them  a state  opposite  to  itself.  The  attraction  is  most  live- 
ly when  the  light  object  is  a conductor,  and  in  contact  with  the 
ground,  since  it  then  more  completely  assumes  an  electric  state  op- 
posed to  that  of  the  inducing  body.  A non-conductor  is  very  im- 
perfectly electrified  by  induction,  because  the  electric  fluids  cannot 
quit  each  other  from  inability  to  move  through  the  non-conductor. 

2.  If  a stick  of  sealing-wax,  strongly  negative,  be  presented  to  a 
thread  or  pith-ball  which  is  also  negatively,  but  feebly,  excited,  re- 
pulsion will  ensue  at  a considerable  distance,  followed  by  attraction 
when  the  distance  is  small.  This  attraction  is  due  to  the  strongly 
excited  wax  acting  by  induction  on  the  feeble  negative  thread,  there- 
by causing  it  to  have  an  excess  of  positive  electricity. 


* According  to  Faraday,  bodies  cannot  be  charged  absolutely,  but  only  relatively,  and 
by  a principle  which  is  the  same  with  that  of  induction  : all  charge  is  sustained  by 
induction;  all  phenomena  of  intensity  include  the  principle  of  induction;  all  excita 
tion  is  dependent  on  or  directly  related  to  induction;  and  all  currents  involve  previous 
intensity  and  therefore  previous  induction, 
t See  Lond.  and  Edin . Philos.  Mag.  Jan.  and  Feb.  1839. 


83 


Leyden  Jar. 

3.  The  positive  electricity  collected  on  the  prime  conductor  of  an  Sect.  v- 
electrical  machine  is  by  some  ascribed,  not  to  a transfer  of  that  fluid 

from  the  glass  to  the  prime  conductor,  but  to  a part  of  the  combined 
electricities  of  the  prime  conductor  being  separated  by  induction,  and 
the  negative  fluid  being  imparted  to  the  positive  glass.  The  same 
view  is  applicable  to  any  system  of  conductors  in  contact  with  the 
prime  conductor,  as  also  to  conductors  connected  with  the  rubber. 

It  is  difficult  to  say  which  explanation  is  the  more  correct,  or  wheth- 
er both  may  not  be  true. 

4.  On  moving  the  hand  towards  the  prime  conductor  of  an  excited 
electrical  machine,  the  hand  becomes  negative  by  induction,  and  the 
spark  ultimately  obtained  restores  the  equilibrium.  In  like  manner 
a negatively  electrified  cloud  renders  positive  a contiguous  tree  or 
tower,  and  then  a stroke  of  lightning  follows  as  a consequence  of 
attraction  between  the  two  accumulated  fluids. 

5.  The  action  of  the  Leyden  Jar  depends  on  the  principle  of  in-  Action  of 
duced  electricity.  A gl^iss  jar  or  bottle  with  a wide  mouth  is  coat-  the  Leyden 
ed  externally  and  internally  with  tinfoil,  except  to  within  three  orjar* 

four  inches  of  its  summit ; and  its  aperture  is  closed  by  dry  wood  or 
some  imperfect  conductor,  through  the  centre  of  which  passes  a me- 
tallic rod  communicating  with  the  tinfoil  on  the  inside  of  the  jar. 

On  placing  the  metallic  rod  in  contact  with  the  prime  conductor  of  an 
excited  electrical  machine,  while  the  outer  coating  communicates 
with  the  ground,  the  interior  of  the  jar  acquires  a charge  of  positive 
electricity,  and  the  exterior  becomes  as  strongly  negative.  If,  the 
jar  being1  insulated,  the  metallic  rod  be  placed  close  to  the  prime 
conductor,  avoiding  actual  contact,  while  an  uninsulated  conductor 
be  held  at  an  equal  distance  from  the  outer  coating,  electric  sparks 
in  equal  number  and  of  equal  size  will  pass  between  both  intervals, 
and  both  sides  of  the  jar  are  found  to  be  in  the  same  condition  as 
before  ; but  no  charge  will  be  received  wheu  the  inner  coating  com- 
municates with  the  prime  conductor,  and  the  outer  coating  is  strictly 
insulated.  From  these  facts  it  is  inferred  that  the  interior  of  the 
jar  becomes  positive,  either  by  receiving  positive  electricity  directly 
from  the  prime  conductor,  or,  as  is  more  probable,  by  communicating 
to  it  negative  electricity  ; and  that  the  exterior  then  becomes  nega- 
tive by  the  loss  of  a quantity  of  positive  electricity  equal  to  that  on 
the  interior.  Unless  means  be  afforded  for  the  escape  of  the  positive 
electricity  from  the  exterior,  no  charge  ought  to  be  received ; and 
this  conclusion  is  quite  conformable  to  the  fact  above  stated. 

274.  The  opposite  electric  fluids  accumulated  on  the  opposite  sides  Leyden  jar. 
of  a charged  Leyden  jar  exert  a strong  mutual  attraction  through  the 
substance  of  the  glass,  and  the  presence  of  each  secures  the  continu- 
ance of  the  other.  The  exterior  of  the  jar  may  be  freely  handled, 
and  its  coating  removed,  without  destroying  the  charge,  provided  no 
communication  be  made  at  the  same  time  with  the  interior ; and  if 
the  exterior  be  insulated,  the  charge  will  be  preserved,  though  the 
tinfoil  of  the  interior  be  removed.  But  when  a conductor  communi- 
cates with  both  surfaces  at  the  same  instant,  the  two  fluids  rush  to- 
gether with  violence,  and  the  equilibrium  is  restored.  Whether  in 
this  and  similar  cases  the  two  fluids  coalesce  entirely  on  the  inter- 
mediate conductor,  or  whether  each  from  its  velocity  may  not  in  part 


84 


Chap.jl. 


Battery. 


Electropho 

rus. 


Mode  of 
using  it. 
The  elec- 
trophorus 
used  as  an 
electric  ma- 
chine. 
Electricity 
from 

change  of 
tempera- 
ture. 


Other 
sources  of 
electricity. 


Electricity. 


pass  the  other,  and  be  projected  to  the  opposite  surface,  is  a question 
on  which  electricians  are  not  agreed. 

275.  The  Leyden  jar  affords  the  means  of  passing  through  bodies 
a large  quantity  of  electricity.  For  not  only  may  jars  of  any  required 
size  be  employed,  but  it  is  easy  so  to  arrange  any  number  of  such 
jars,  that  they  shall  all  be  charged  and  discharged  at  the  same  time, 
constituting  what  is  termed  an  Electrical  Battery.  The  arrange- 
ment is  made,  by  placing  a number  of  Leyden  jars  in  a box  lined 
with  tinfoil,  by  which  means  their  outer  surfaces  have  free  metallic 
communication  with  each  other,  and  connecting  their  inner  surfaces 
by  wires.  T.  78. 

276.  The  operation  of  the  instrument  called  the  Electrophones  (or 
bearer  of  electricity)  is  referable  to  the  phenomena  of  induction. 


. The  electrophorus  (Fig.  57),  consists  of  two  metallic  plates.  Fig-  57. 

a a,  with  an  intervening  plate  of  resinous  matter,  4,  for  which  Q 

equal  parts  of  shellac,  resin,  and  Venice  turpentine,  are  ge- 
nerally used,  the  mixture  being  carefully  melted  in  a pipkin,  L 

and  poured,  whilst  liquid,  into  a wooden  or  metal  hoop,  of  a l 

proper  size,  placed  upon  a polished  surface  of  glass  or  marble,  Jl 

from  which  it  easily  separates  when  cold ; it  should  be  about 
half  an  inch  thick,  and  the  smooth  surface  being  uppermost 
the  lower  side  should  bo  covered  with  tinfoil,  or  attached  to  1 -« 

any  other  metallic  plate;  a polished  brass  plate,  with  a glass  handle  c attached  to 
it,  is  then  placed  upon  the  upper  surface  of  trie  resinous  plate,  and  of  rather  smaller 
diameter. 


The  resin  is  excited  with  a piece  of  dry  fur,  and  the  instrument 
will  be  found  to  exhibit  the  following  phenomena  : — Upon  raising  the 
brass  plate  by  its  insulating  handle,  it  will  be  found  very  feebly 
electrical ; replace  it,  touch  it  with  the  finger  an&again  lift  it  off  by 
its  handle,  and  it  will  give  a spark  of  positive  electricity.  This  pro- 
cess may  very  often  be  repeated  without  fresh  excitation.*  The 
electrophorus  may  often  be  used  for  the  same  purpose  as  the  electri- 
cal machine,  and  in  the  laboratory  it  furnishes  a very  convenient  sub- 
‘ stitute  for  that  more  expensive  piece  of  apparatus.! 

277.  Electricity  is  excited  also  by  change  of  temperature.  The 
electric  equilibrium  is  disturbed  in  metallic  rods  or  wires  when  one 
extremity  has  a different  temperature  from  that  of  the  other,  whether 
the  difference  be  effected  by  the  application  of  heat  or  cold.  The 
experiment  is  usually  made  by  heating  or  cooling  the  point  of  junc- 
tion of  two  metallic  wires,  which  are  soldered  together;  but  Bec- 
querel  has  proved  that  the  contact  of  different  metals  is  not  essential.! 

278.  There  are  many  other  sources  of  electricity.  When  glass  is 
rubbed  by  mercury,  it  becomes  electrified,  and  this  is  the  cause  of 
the  luminous  appearance  observed  when  a barometer  is  agitated  in  a 
dark  room,  in  which  case  flashes  of  light  are  seen  to  traverse  the 
empty  part  of  the  tube.  Even  the  friction  of  air  upon  glass  is  at- 
tended by  electrical  excitation.  Whenever  bodies  change  their 
forms,  their  electrical  states  are  also  altered.  Thus  during  the  con- 
gelation of  melted  resins  and  sulphur,  electricity  is  rendered  sensible. 
It  is  also  developed  during  various  natural  processes;  as  evaporation 


* Ample  directions  for  constructing  this  useful  instrument,  and  for  applying  electri- 
city in  tne  laboratory,  will  be  found  in  Faraday’s  Cfiem.  Manipulation,  p.  436. 
tFor  a more  full  account,  see  Turner’s  Elements,  Sect.  111. 
t An.  de  Chem.  et  de  Phys.  xli.  353,  An.  Philos.,  N.  S.,  v.  427,  and  Phil.  Mag.  iii. 


Voltaic  Circles , 


85 


and  the  condensation  of  vapour,  which  may  aid  in  accounting  for  Sect,  v. 
certain  electrical  phenomena  of  the  atmosphere. 

Place  a small  iron  cup,  heated  nearly  to  redness,  over  an  electrometer ; on  Exp. 
dropping  into  it  a small  portion  of  water,  vapour  will  be  produced,  and  the  leaves 
of  the  electrometer  will  diverge. 


279.  Another  reputed  source  of  electricity  is  contact  of  different  Electricity 
substances,  especially  of  metals;  a source  originally  suggested  ^>y  contact  of 
Volta,  who  founded  on  it  his  theory  of  galvanism.  When  a plate  ofmetals. 
zinc  furnished  with  a glass  handle  is  brought  into  contact  with  one 
of  copper  or  silver,  it  is  found,  after  removal,  to  he  positively  electri- 
cal, and  the  silver  or  copper  is  left  in  the  opposite  state. 

The  electricity  thus  developed  was  distinguished  as  Galvanism,  Galvanism, 
from  the  circumstance  that  Galvani,  an  Italian  physiologist,  about 
the  year  1789,  observed  the  first  striking  phenomenon  which  led  to 
the  discovery.  He  observed  it  only  in  its  power  of  affecting  the  ani- 
mal system.  It  was  found  that  if  the  nerve  of  a recently  killed  frog 
was  attached  to  a silver  probe,  and  a piece  of  zinc  was  brought  into 
contact  with  the  muscles  of  the  animal,  violent  contractions  would 
be  produced  at  every  contact  of  the  metals.  Exactly  the  same  effect 
is  produced  by  an  electric  spark,  or  the  discharge  of  a small  Leyden 
phial.  The  following  experiment  produces  a similar  effect. 

Place  a piece  of  zinc  upon  the  tongue,  and  a piece  of  silver  under  it ; when- 
ever  the  projecting  edges  of  these  different  metals  are  made  to  touch,  a peculiar 
taste  or  sensation  will  be  perceived,  and  if  the  pieces  are  large  the  contact  will 
sometimes  be  accompanied  by  a flash  of  light. 


280.  From  these  and  similar  experiments  Galvani  concluded  that  Galvani’s 
the  phenomena  were  owing  to  the  communication  of  electricity  ge-  ypot  esis’ 
nerated  by  the  animal  system.  Volta  supposed  that  the  electricity  Volta’s 
was  derived  from  the  action  exerted  between  the  metal  and  the 

moist  animal  fibre,  and  soon  discovered  that  it  is  evolved  by  arrange- 
ments wholly  unconnected  with  any  process  of  vitality.  His  disco- 
very of  a method  of  augmenting  the  galvanic  energy,  and  of  thus 
enabling  us  to  investigate  its  effects  with  more  precision,  has  ac- 
quired for  this  form  of  electricity  the  epithet  Voltaic. 

281.  The  identity  of  the  agent  concerned  in  the  phenomena  of 
galvanism  and  of  the  common  electrical  machine,  is  now  a matter  of 
demonstration.  The  effects  of  common  electricity  are  caused  by  a 
comparatively  small  quantity  of  electricity  brought  into  a state  of  in- 
sulation, in  which  state  it  exerts  a high  intensity,  as  evinced  by  its 
remarkable  attractive  and  repulsive  energies,  and  by  its  power  to 
force  a passage  through  obstructing  media.  In  galvanism  the  elec- 
tric agent  is  more  intimately  associated  with  other  substances,  is 
developed  in  large  quantity,  but  never  attains  a high  tension,  and 
produces  its  peculiar  effects  while  flowing  along  conductors  in  a con- 
tinuous current. 

282.  When  a plate  of  zinc  and  a plate  of  copper  are  placed  in  a Simple 
vessel  of  water,  and  the  two  metals  are  made  to  touch  each  other,  Y^Jj^0 
either  directly  or  by  the  intervention  of  a metallic  wire,  galvanism  is  C11C  es* 
excited.  The  action  is,  indeed,  very  feeble,  and  not  to  be  detected 

by  ordinary  methods  ; but  if  a little  sulphuric  acid  be  added  to  the 
water,  numerous  globules  of  hydrogen  gas  will  be  evolved  at  the  sur- 
face of  the  copper.  This  continues  while  metallic  contact  between 
the  plates  continues,  in  which  state  the  circuit  is  said  to  be  closed  ; 


86 


Chap.  I. 


Circle  of 
metal  and 
liquid. 


Zicc  circle. 


Electricity — Voltaic. 


idi  ! 

1 1 • 

y 

_ 

but  it  ceases  when  the  circuit  is  broken,  that  is,  when  metallic  contact 
is  interrupted.  The  hydrogen  gas  which  arises  from  the  copper 
plate  results  from  water  decomposed  by  the  electric  current,  and  its 
ceasing  to  appear  indicates  the  moment  when  the  current  ceases.  In 
this  case  the  voltaic  circle  consists  of  zinc,  copper,  and  interposed  di- 
lute acid  ; and  the  circle  gives  rise  to  a current  only  when  the  two 
metals  are  in  contact.  This  arrangement  is  shown  in  Fig.  59,  where 
metallic  contact  is  readily  made  or  broken  by  ^ Fig.  58. 
means  of  copper  wires  soldered  to  the  plates.  It 
is  found  that  a current  of  positive  electricity  con- 
tinually circulates  in  the  closed  circuit  from  the 
zinc  through  the  liquid  to  the  copper,  and  from 
the  copper  along  the  conducting  wires  to  the 
zinc,  as  indicated  by  the  arrows  in  the  figure.  A 
current  of  negative  electricity,  agreeably  to  the  theory  of  two  electric 
fluids,  ought  to  traverse  the  apparatus  in  a direction  precisely  re- 
versed ; but  for  the  sake  of  simplicity  the  course  of  the  positive  cur- 
rent only  will  hereafter  be  indicated. 

293.  It  matters  not,  so  far  as  voltaic  action  is  concerned,  at  what 
part  the  plates  touch  each  other.  Immersion  of  one  plate  only  in 
the  acid  solution,  however  contact  between  the  plates  may  be  made, 
does  not  excite  voltaic  action  ; nor  does  it  suffice  to  have  one  plate  in 
one  vessel,  and  the  other  plate  in  another  vessel.  A plate  of  zinc 
soldered  to  one  of  copper,  and  plunged  into  dilute  acid,  gives  a cur- 
rent passing  from  the  zinc  through  the  fluid  round  to  the  copper : 
but  if  the  soldered  plates  are  cemented  into  a box  with 
a wooden  bottom  and  metallic  sides,  so  as  to  form  two 
separate  cells,  as  shown  in  a vertical  section  by  Fig. 

59,  then  the  introduction  of  dilute  acid  to  the  cells  will 
not  excite  a current  unless  the  fluid  of  the  cells  be 
made  to  communicate  by  means  of  moistened  fibres  of 
twine,  cotton,  or  some  porous  matter,  or,  as  in  the  figure, 
by  wires  a b%  soldered  to  the  metallic  sides  which  contain  the  dilute 
acid,  or  dipping  into  the  acid  itself.  Then  the  positive  current  cir- 
culates in  the  direction  shown  by  the  arrows. 

Instead  of  a pair  of  plates  being  soldered  together,  they  may  be 
connected  by  a wire,  and  plunged  into  separate  cells. 

294.  A simple  voltaic  circle  may  be  formed  of  one  metal  and  two 
liquids,  provided  the  liquids  are  such  that  a stronger  chemical  action 
is  induced  on  one  side  than  on  the  other.  Nay,  the  same  acid  solution 
may  occupy  both  cells,  provided  some  condition  be  introduced  which 
shall  cause  one  side  of  the  zinc  to  be  more  rapidly  dissolved  than  the 
other;  as  by  the  plate  being  rough  on  one  side  and  polished  on  the 
other,  or  by  the  acid  being  hot  in  one  cell  ancl  cold  in  the  other.  In 
this  case,  however,  the  result  is  the  same  as  though  two  different 
liquids  were  used. 

295  An  interesting  kind  of  simple  voltaic  circle  is  afforded  by 
commercial  zinc  This  metal,  as  sold  in  the  shops,  contains  traces 
of  tin  and  lead,  with  rather  more  than  one  per  cent,  of  iron,  which  is 
mechanically  diffused  through  its  substance  : on  immersion  in  dilute 
sulphuric  acid,  these  small  particles  of  iron  and  the  adjacent  zinc 


Voltaic  Circles.  S7 

form  numerous  voltaic  circles,  transmitting  their  currents  through  sec.  v. 
the  acid  which  moistens  them,  and  disengaging  a large  quantity  of 
hydrogen  gas.^ 

286.  While  the  current  formed  by  the  contact  of  two  metals  gives 
increased  effect  to  the  affinity  of  one  of  them  for  some  element  of  the 
solution,  the  ability  of  the  other  metal  to  undergo  the  same  change 
is  proportionally  diminished.  Thus,  when  plates  of  zinc  and  copper 
touch  each  other  in  dilute  acid,  the  zinc  oxidizes  more,  and  the  cop- 
per less,  rapidly  than  without  contact.  This  principle  was  beauti-  Davy.s 
fully  exemplified  by  the  attempt  of  Davy  to  preserve  the  copper  protector, 
sheathing  of  ships.  Davy  found  that  the  quantity  of  zinc  required 

to  form  an  efficient  voltaic  circle  with  copper  was  very  small.!  Un- 
happily, in  practice,  it  is  found  that  unless  a certain  degree  of  cor- 
rosion takes  place  in  the  copper,  its  surface  becomes  foul  from  the 
adhesion  of  sea-weeds  and  shell-fish. 

287.  Simple  voltaic  circles  may  be  formed  of  various  materials  ; Other  cir- 
but  the  combinations  usually  employed  consist  either  of  two  perfect cles< 
and  one  imperfect  conductor  of  electricity,  or  of  one  perfect  and  two 
imperfect  conductors.  The  substances  included  under  the  title  of 
perfect  conductors  are  metals  and  charcoal,  and  the  imperfect  con- 
ductors are  water  and  aqueous  solutions.  It  is  essential  to  the  ope- 
ration of  the  first  kind  of  circle,  that  the  imperfect  conductor  act 
chemically  on  one  of  the  metals  : and  in  case  of  its  attacking  both, 

the  action  must  be  greater  on  one  metal  than  on  the  other.  It  is 
also  found  generally,  if  not  universally,  that  the  metal  most  attacked 
is  positive  with  respect  to  the  other,  or  bears  to  it  the  same  relation 
as  zinc  to  copper.! 

288.  The  presence  of  water  has  been  shown  by  Faraday  not  to  be  Water  not 
essential.  A battery  may  be  composed  of  other  liquid  compounds,  essential* 
such  as  a fused  metallic  chloride,  iodide,  or  fluoride,  provided  it  is 
decomposable  by  galvanism,  and  acts  chemically  on  one  metal  of  the 

circle  more  powerfully  than  on  the  other. 

The  following  table  of  voltaic  circles  of  the  second  kind  is  from 
Davy’s  Elements  of  Chemical  Philosophy  : — 


* Mr  Sturgeon  has  remarked  that  commercial  zinc,  with  its  surface  amalgamated, 
which  may  be  done  by  dipping  a zinc  plate  iuto  nitric  acid  diluted  with  two  or  three 
parts  of  water,  and  then  rubbing  it  with  mercury,  resists  the  action  of  dilute  acid  fully 
as  well  as  the  purest  zinc.  This  fact,  of  which  Faraday  in  his  late  researches  has 
made  excellent  use,  appears  due  to  the  mercury  bringing  the  surface  of  the  zinc  to  a 
state  of  perfect  uniformity,  preventing  those  differences  between  one  spot  and  another, 
which  are  essential  to  the  production  of  minute  currents  ; one  part  has  the  same  ten- 
dency to  combine  with  electricity  as  another,  and  cannot  act  as  a discharger  to  it  (Fa- 
raday). 

t Phil.  Trans.  1824. 

tDavy,  in  his  Bakerian  lecture  for  1826  (Phil.  Trans.),  gave  the  following  list  of 
the  first  kind  of  arrangements,  the  imperfect  conductor  being  either  the  common  acids, 
alkaline  solutions,  or  solutions  of  metallic  sulphurets,  such  as  sulphuret  of  potassium. 
The  metal  first  mentioned  is  positive  to  those  standing  after  it  in  the  series. 

With  common  acids. — Potassium  and  its  amalgams,  barium  and  its  amalgams, 
amalgam  of  zinc,  cadmium,  tin,  iron,  bismuth,  antimony,  lead,  copper,  silver,  palladi- 
um, tellurium,  gold,  charcoal,  platinum,  iridium,  rhodium. 

With  alkaline  solutions — The  alkaligenous  metals  and  their  amalgams,  zinc,  tin, 
lead,  copper,  iron,  silver,  palladium,  gold,  and  platinum. 

With  solutions  of  metallic  sulphurets.— Zinc,  tin,  copper,  iron,  bismuth,  silver,  pla- 
tinum, palladium,  gold,  charcoal. 


88 


Electricity — Voltaic. 


Chap  I. 


Exp. 


Metals  not 
essential. 


Circles 
most  used. 


Solution  of  sulphuret  of  potassium 

Copper 

Nitric  acid 

potassa 

Silver 

Sulphuric  acid 

soda 

Lead 

Tin 

Zinc 

Other  metals 
Charcoal 

Hydrochloric  acid 
Any  solutions  contain- 
ing acid. 

The  most  energetic  of  these  combinations  is  that  in  which  the 
metal  is  chemically  attacked  on  one  side  by  sulphuret  of  potassium, 
and  on  the  other  by  an  acid.  The  experiment  may  be  made  by  pour- 
ing dilute  nitric  acid  into  a cup  of  copper  or  silver,  which  stands  in 
another  vessel  containing  sulphuret  of  potassium.  The  following 
arrangements  may  also  be  employed  : — 

Let  two  pieces  of  thick  flannel  be  moistened,  one  with  dilate  acid  and  the 
other  with  the  sulphuret,  and  then  placed  on  opposite  sides  of  a plate  of  copper, 
completing  the  circuit  by  touching  each  piece  of  flannel  with  a conducting  wire  : 
or,  take  two  discs  of  copper,  each  with  its  appropriate  wire,  immerse  one  disk 
into  a glass  filled  with  dilute  acid,  and  the  other  into  a separate  glass  with  alka- 
line solution,  and  connect  the  two  vessels  by  a few  threads  of  amianthus  or  cotton 
moistened  with  a solution  of  salt.  A similar  combination  may  be  disposed  in 
this  order  : let  one  disc  of  copper  be  placed  on  a piece  of  glass  or  dry  wood  ; on 
its  upper  surface  lay  in  succession  three  pieces  of  flannel,  the  first  moistened 
with  dilute  acid,  the  second  with  solution  of  salt,  and  the  third  with  sulphuret  of 
potassium,  and  then  cover  the  last  with  the  other  disc  of  copper. 


’ 2S9.  Metallic  bodies  are  not  essential  to  the  production  of  galvanic 

phenomena.  Combinations  have  been  made  with  layers  of  charcoal 
and  plumbago,  of  slices  of  muscle  and  brain,  and  beet-root  and  wood; 
but  the  force  of  these  circles  though  accumulated  by  the  union  of 
numerous  pairs,  is  extremely  feeble,  and  they  are  very  rarely  em- 
ployed in  practice. 

290.  Of  the  simple  voltaic  circles  above  described,  the  one  used 
for  ordinary  purposes  is  that  composed  of  a pair  of  zinc  and  copper 
plates  excited  by  an  acid  solution  arranged  as  in  Fig.  58.  The  form 
and  size  of  the  apparatus  are  exceedingly  various.  Instead  of  actu- 
ally immersing  the  plates  in  the  solution,  a piece  of  moistened  cloth 
may  be  placed  between  them.  Sometimes  the  copper  plate  is 
made  into  a cup  for  contaiping  the  liquid,  and  the  Fig.60. 
zinc  is  fixed  between  its  two  sides,  as  shown  by  the 
accompanying  transverse  vertical  section,  Fig.  60  ; 
care  being  taken  to  avoid  actual  contact  between  the 
plates,  by  interposing  pieces  of  wood,  cork,  or  other 
imperfect  conductor  of  electricity.  T.  9i.  Another  con- 
trivance, which  fs  much  more  convenient,  because  the 
zinc  may  be  removed  at  will  and  have  its  surface  cleaned,  is  that 
represented  by  Fig.  61.  An  earthen  pot  a a is 
lined  with  a cylinder  of  thin  copper,  within  which 
are  one  or  more  smaller  cylinders  of  the  same, 
connected  at  bottom  by  narrow  pieces  of  cop- 
per. One,  or  more  cylinders  of  zinc  are  placed  in 
the  space  between  the  coppers,  being  somewhat 
shorter  than  the  copper  cylinders,  and  are  support- 
ed on  the  edge  of  the  pot  by  projecting  pieces  sol- 
dered to  the  upper  edges.  (Fig.  62.)  Small  cups 


[=3 


Fig.  61. 


4 


Hare’s  Calorimotor . 


89 


are  attached  to  the  two  metals  for  receiv- 
ing a few  drops  of  mercury,  into  which 
the  ends  of  wires  may  be  dipped  and  the 
circuit  be  closed  or  broken  at  pleasure. 

This  apparatus  is  very  serviceable  in  expe- 
riments on  electro-magnetism.  The  liquid 
employed  is  a solution  of  sulphate  of  cop- 
per (blue  vitriol)  in  water,  and  may  be  allowed  to  remain  in  the  pot 
when  the  apparatus  is  not  in  use,  all  that  is  necessary  is  to  remove 
the  zinc  cylinder. 

Another  kind  of  circle  may  be  formed  by  coiling  a sheet  of  zinc 
and  copper  round  each  other,  so  that  each  surface  of  the  zinc  may 
be  opposed  to  one  of  copper,  and  separated  from  it  by  a small  inter- 
val. The  contrivance  of  opposing  one  large  connected  surface  of 
zinc  to  a similar  surface  of  copper,  originated  with  Hare  of  Phil- 
adelphia, who,  from  its  surprising  power  of  igniting  metals,  gave  it 
the  name  of  Calorimotor 

291.  Compound  voltaic  circles  consist  of  a series  of  simple  circles. 
The  first  combinations  of  the  kind  were  described  by  Volta,  and  are 


Fig.  62. 


* A a,  represent  two  cubical  vessels, 
twenty  inches  square,  inside,  b b , 
a frame  of  wood  containing  20  sheets 
of  copper,  and  20  sheets  of  zinc,  alter- 
nating with  each  other,  and  about  half 
an  inch  apart.  T T It,  masses  of  tin 
cast  over  the  protruding  edges  of  the 
sheets  which  are  to  communicate  with 
each  other.  The  small  fig.  on  the  right, 
represents  the  modem  which  the  junc- 
tion between  the  various  sheets  and 
tin  masses  is  effected.  The  zinc  only 
is  in  contact  with  the  tin  on  one 
side ; the  copper  alone  touches  on 
the  other.  At  the  back  of  the  frame, 
ten  sheets  of  copper  and  ten  sheets  of 
zinc  are  made  to  communicate,  by  a 
common  mass  of  tin  extending  the 
whole  length  of  the  frame,  between  T 
T ; but  in  front,  as  in  Fig.  63,  there  is 
an  interstice  between  the  mass  of  tin 
connecting  the  ten  copper  sheets,  and 
that  connecting  the  ten  zinc  sheets.  The  screw  forceps,  appertaining  to  each  of  the 
tin  masses,  may  be  seen  on  either  side  of  the  interstice  ; and  likewise  a wire  for  igni- 
tion held  between  them.  The  application  of  the  rope,  pulley,  and  weights  is  obvi- 
ous. The  frame  can  be  swung  round  and  lowered  into  the  water  in  the'- vessel  a,  to 
wash  off  the  acid,  which,  after  immersion  in  the  other  vessel,  might  continue  to  act  on 
the  sheets,  incrusting  them  with  oxide. 

When  the  copper  and  zinc  surfaces  are  united  by  an  intervening  wire,  and  the  in- 
strument is  immersed  in  the  acid  liquor  in  the  vessel  beneath,  the  wire  becomes  in- 
tensely ignited,  and  when  hydrogen  is  liberated  in  sufficient  quantity  it  usually  takes 
fire  producing  a very  beautiful  corruscating  flame  upon  the  surface  of  the  liquid.*  Or 
the  following  method  may  be  employed  : cut  the  plates  into  the  Fi  64 

Fig.  65.  form  represented  in  Fig.  64,  solder  the  zinc  . . S' — 

and  copper  together,  bend  them  into  the  c TT 

form  of  Fig. 65  and  arrange  them  in  the  1 J 

trough  as  in  Fig.  72.  The  zinc  plates  are  kept  from  touching 
the  copper  plates  by  pieces  of  cork,  and  pieces  of  thick  paper  are 
interposed  bet  ween  the  contiguous  surfaces  of  copper.  Faraday,  ‘ 
in  Phil.  Trans.  1835. 


* See  Jhner.  Jour . of  Science,  vol.  i.  413. 


Sect.  V. 


Circular 

arrange- 

ment. 


Compound 

circles. 


Hare’s  im- 
prorement. 


Calorimoter- 


12 


90 


Chap.  I. 


Position  of 
the  metals. 


Trough. 


Electricity — Voltaic , 

now  well  known  under  the  names  of  voltaic  pile  and  crown  of  cups. 
(Fig.  66).  In  this  apparatus  the  exciting  so-  Fig-  6G- 

lution  is  contained  in  separate  glasses  or 
cups ; each  glass  contains  a pair  of  plates, 
and  each  zinc  plate  is  attached  to  the  cop- 
per of  the  next  pair  by  a metallic  wire.  The 
voltaic  pile  is  made  by  placing  pairs  of  zinc 
and  copper,  or  zinc  and  silver  plates  one 
above  the  other,  as  shown  in  Fig.  67,  each  pair  separated  from 
those  adjoining  by  pieces  of  cloth  rather  smaller  than  the 
plates,  and  moistened  with  a saturated  solution  of  salt. 

The  relative  position  of  the  metals  in  each  pair  must  be 
the  same  in  the  whole  series  ; that  is,  if  the  zinc  be  placed 
below  the  copper  in  the  first  pair,  the  same  order  should 
be  observed  in  all  the  others.  Without  such  precaution 
the  apparatus  would  give  rise  to  opposite  currents, 
which  would  neutralize  each  other  more  or  less  accord- 
ing to  their  relative  forces.  The  pile,  which  may  con- 
sist of  any  convenient  number  of  combinations,  should 
be  contained  in  a frame  formed  of  glass  pillars  fixed  into  a piece  of 
thick  dry  wood,  by  which  it  is  both  supported  and  insulated.  Any 
number  of  these  piles  tnay  be  made  to  act  in  concert  by  establishing 
metallic  communication  between  the  positive  extremity  of  each 
pile  and  the  negative  extremity  of  the  pile  immediately  following. 

292.  The  voltaic  pile  is  now  rarely  employed,  because  we  possess 
other  modes  of  forming  galvanic  combinations  which  are  far  more 
powerful  and  convenient.  The  galvanic  battery  proposed  by  Cruik- 
shank,  consists  of  a trough  of  baked  wood,  about  30  inches  long,  in 
which  are  placed  at  equal  distances  50  pairs  of 
zinc  and  copper  plates  previously  soldered  to- 
gether, and  so  arranged  that  the  same  metal 
shall  always  be  on  the  same  side.  Each  pair 
is  fixed  in  a groove  cut  in  the  sides  and  bottom 
of  the  box,  the  points  of  junction  being  made 
water-tight  by  cement.  The  apparatus  thus 
constructed  is  always  ready  for  use,  and  is 
brought  into  action  by  filling  the  cells  left  between  the  pairs  of  plates 
with  some  convenient  solution,  which  serves  the  same  purpose  as  the 
moistened  cloth  in  the  pile  of  Volta.  By  means  of  Figs.  68  and 
69  the  mode  in  which  the  plates  are  arranged  will  easily  be  under- 
stood. 

293.  Other  modes  of  combination  are  now  in  use,  which  facilitate 
the  employment  of  the  voltaic  apparatus  and  increase  its  energy. 
Most  of  these  may  be  regarded  as  modifications  of  the  crown  of  cups. 
Instead  of  glasses  it  is  more  convenient  to  employ  a trough  of  baked 
wood,  (Fig.  69),  or  glazed  earthenware, 
divided  into  separate  cells  by  partitions  of 
the  same  material  ; and  in  order  that  the 
plates  may  be  immersed  into  and  taken 
out  of  the  liquid  conveniently  and  at  the  same  moment,  they  are  all 
attached  to  a bar  of  dry  wood,  the  necessary  connexion  between 


Fig.  69. 


I 


Fig.  68. 


Compound  Circles. 


91 


the  zinc  of  one  cell  and  the  copper  of  the 
adjoining  one  being  accomplished,  as 
shown  in  figure  70,  by  a slip  or  wire  of 
copper.^ 

294.  The  size  and  number  of  the  plates 
may  be  varied  at  pleasure.  The  common 
and  most  convenient  size  for  the  plates,  is 
four  or  six  inches  square  ; and  when  great 
power  is  required,  a number  of  different 
batteries  are  united  by  establishing  metal- 
lic communication  between  the  positive 
extremity  of  one  battery  and  the  negative  extremity  of  the  adjoin- 
ing one.  The  great  battery  of  the  Royal  Institution,  with  which 
Davy  made  his  celebrated  discovery  of  the  compound  nature  of  the  al- 
kalies, was  composed  of  2000  pairs  of  plates,  each  plate  having  32 
square  inches  of  surface.  It  is  now  recognized,  however,  that  such 
large  compound  batteries  are  by  no  means  necessary.  Increasing  the 
number  of  plates  beyond  a very  moderate  limit  gives,  for  most  purpos- 
es, no  proportionate  increase  of  power ; so  that  a battery  of  50  or  100 
pairs  of  plates,  thrown  into  vigorous  action,  will  be  just  as  effective 
as  one  of  far  greater  extent. 

295.  The  electrical  condition  of  compound  voltaic  arrangements  is  Condition 
similar  to  that  of  the  simple  circle.  In  the  broken  circuit  no  electric  ’ir_ 
current  can  be  traced  ; but  in  the -closed  circuit,  that  is,  when  the  cles. 
wires  from  the  opposite  ends  of  the  battery  are  in  contact,  the  galva- 
nometer indicates  a positive  electric  current  through  the  battery  itself 


* A material  improvement  in  the  apparatus  was  made  by- 
Wollaston,  which  consisted  in  extending  the  copper  plate,  so 
as  to  oppose  it  to  every  surface,  of  the  zinc,  as  seen  in  Fig.  71. 

A is  the  rod  of  wood  to  which  the  plates  are  screwed ; b b the 
zinc  plates  connected  as  usual  with  the  copper  plates  c c, 
which  are  doubled  over  the  zinc  plates,  and  opposed  to  them 
upon  all  sides,  contact  of  the  surfaces  being  prevented  by 
pieces  of  wood  or  cork  placed  at  d d.  Hare  adopted  this  with 
great  advantage  in  his  Deflagrator.  (Fig.  72.)  It  consists  of  four 
troughs  a a,  b b,  each  10  feet  long.  Each  two  of  the  troughs 
are  joined  lengthwise,  edge  to  edge,  so  that  when  the  sides  of 
the  two  b b are  vertical,  those  of  the  others  a a are  horizontal. 

The  troughs  are  supported  by  a frame  c c,  and  turn  upon  pi- 
vots d d.  The  pivots  are  made  of  iron  coated  with  brass  or  copper,  and  a communi-  Hare’s  Defe- 
cation is  made  between  these  and  the  galvanic  series  within  by  strips  of  copper  e.  grator. 


Fig.  72. 


Fig.  73. 


Fig.  74. 


The  galvanic  series  of  300  pairs  of  copper  and  zinc  plates  (connected  as  in  Figs.  73 
and  74,  each  zinc  plate  z being  between  two  copper  plates  c c)  are  placed  in  the  troughs 
a a,.*  The  acid  liquor  is  contained  in  the  troughs  b b,  and  by  a partial  revolution  of 
the  apparatus  is  made  to  flow  into  the  troughs  containing  the  plates. 


* See  Amer.  Jour.  iii.  347. 


92 


Electricity — Voltaic. 


Chap.  I. 


Evolution 
of  hydro- 
gen. 


Theories  of 
Galvanism. 
Volta’s, 


Wollas- 

ton’s, 


and  along  the  wires,  as  shown  by  the  arrows  in  Figs.  66  and  68. 
The  direction  of  the  current  appears  at  first  view  to  be  different  from 
that  of  the  simple  circle;  since  in  the  latter  the  positive  electric  cur- 
rent flows  from  the  zinc  through  the  liquid  to  the  copper,  while  in 
the  compound  circle  its  direction  is  from  the  extreme  copper  through 
the  battery  to  the  extreme  zinc  plate.  This  apparent  difference 
arises  from  the  compound  circle  being  usually  terminated  by  two 
superfluous  plates.  The  extreme  copper  and  extreme  zinc  plate  of 
Fig.  68  are  not  in  contact  with  the  exciting  fluid,  and  therefore  con- 
tribute nothing  to  the  galvanic  action : removing  these  superfluous 
plates,  which  are  solely  conductors,  there  will  remain  four  simple 
circles,  namely,  the  three  pair  of  soldered  plates  marked  2,  3,  4, 
which  act  as  in  Fig.  59,  and  the  then  extreme  plates,  1,  1,  which 
are  related  to  each  other  as  the  plates  in  Fig.  58.  When  thus  ar- 
ranged, the  direction  of  the  current  will  be  seen  to  correspond  with 
that  of  the  simple  circle. 

296.  During  the  action  of  a simple  circle,  as  of  zinc  and  copper, 
excited  by  dilute  sulphuric  acid,  all  of  the  hydrogen  developed  in  the 
voltaic  process  is  evolved  at  the  surface  of  the  copper.  This  fact  is 
not  apparent  when  common  zinc  plates  are  used,  owing  to  the  nu- 
merous currents  which  form  on  the  surface  of  the  zinc  (285)  ; 
but  when  a plate  of  amalgamated  zinc  and  another  of  platinum  are 
introduced  into  dilute  sulphuric  acid  of  specific  gravity  1.068  or  a 
little  higher,  no  gas  whatever  appears  until  contact  between  the 
plates  is  made,  and  then  hydrogen  gas  rises  solely  from  the  platinum, 
while  zinc  is  tranquilly  dissolved.  The  separation  of  one  ingredient 
of  the  exciting  solution  at  one  plate,  while  the  element  previously 
combined  with  it  unites  with  the  other  plate,  seems  essen- 
tial to  voltaic  action.  It  is  in  some  way  connected  with  the  passage 
of  the  current  across  the  exciting  liquid. 

297.  Among  the  different  kinds  of  voltaic  apparatus  is  usually- 
placed  the  electFic  column  of  De  Luc,  which  is  formed  of  successive 
pairs  of  silver  and  zinc,  or  silver  and  Dutch-metal  leaf,  separated  by 
pieces  of  paper  arranged  as  in  a voltaic  pile.  It  is  remarkable  for 
its  power  of  exhibiting  attractions  and  repulsions  like  common  elec- 
tricity, but  cannot  produce  chemical  decomposition  or  any  of  the 
effects  most  characteristic  of  a voltaic  current,  and  is  rather  an  elec- 
trical than  a voltaic  instrument.*  T.  94. 

298.  Several  theories  have  been  proposed  for  the  explanation  of 
galvanism  and  its  effects.  Volta  conceived  that  electricity  was  set 
in  motion  and  kept  up,  solely  by  the  contact  or  communication  be- 
tween the  metals.  He  regarded  the  interposed  solution  merely  as  a 
conductor,  by  means  of  which  the  electricity  of  each  pair  of  plates  is 
conveyed  from  one  part  of  the  apparatus  to  the  other. 

299.  The  second  theory  is  that  of  Wollaston,  who  assigned  chemi- 
cal action  as  the  cause  of  the  electricity  excited.  He  concluded  that 
the  process  begins  with  the  oxidation  of  the  zinc,  and  that  the  con- 


De  t.uc’ic*i-  *Fig.  2,  Frontispiece,  represents  De  Luc’s  columns,  with  a metallic  ball  suspended 
umn«  between  them.  The  glass  tubes  are  packed  with  1000  or  1500  pairs  of  zinc  and  silver 

disks,  the  series  commencing  with  zinc  in  one,  and  with  silver  in  the  other;  the  co- 
lumns terminate  at  bottom  in  small  bells,  between  which  the  ball  is  attracted  and 
repelled  for  a considerable  length  of  time,  producing  an  irregular  chime.  See  Singer’* 
Electricity , 452. 


Faraday^s  Experiments . 


93 


Fig.  75, 
£■ 


Faraday’s 

Exp’ts. 


tact  of  the  plates  served  only  to  conduct  electricity.  The  third  the-  Sect,  v. 
ory  was  that  proposed  by  Davy,  who  maintained  that,  though  not 
the  primary  movers  of  the  electric  current,  the  chemical  changes  are  Davys’ 
essential  to  the  continued  action  of  every  voltaic  circle.  The  elec- 
tric excitement  was  begun,  he  thought,  by  metallic  contact,  and  main- 
tained by  chemical  action. 

300.  Conclusive  evidence  against  the  theory  of  Volta  has  very 
recently  been  obtained  by  Faraday.^  He  proved  metallic  contact 
not  to  be  essential  to  voltaic  action,  by  procuring  that  action  quite 
characteristically  without  contact. 

A plate  of  zinc,  a,  Fig.  75,  about  8 inches  long  by  £ an  inch  wide, 

Was  cleaned  and  bent  at  a right  angle  : and  a plate  of  platinum,  oi 
the  same  width  and  three  inches  long,  was  soldered  to  a platinum 
wire,  b s x,  the  point  of  which,  x , rested  on  a piece  of  bibulous  pa- 
per lying  upon  the  zinc,  and  moistened  with  a solution  of  iodide  of 
potassium.  On  introducing  the  plates  into  a vessel,  c,  filled  with 
dilute  sulphuric  and  nitric  acid,  a positive  electric  current  instantly 
ensued  in  the  direction  of  the  arrow,  as  testified  by  the  hydrogen 
evolved  at  the  plate  a,  by  the  decomposed  iodide  of  potassium,  and 
by  a galvanometer.  We  have  thus  a simple  circle  of  the  same  con- 
struction and  action  as  in  Figure  58,  except  in  the  absence  of  me- 
tallic Contact. 

Another  proof,  aptly  cited  by  Faraday,  of  electric  ex- 
citement being  independent  of  contact,  is  afforded  by  the  spark 
which  appears,  when  the  wires  of  a pair  of  plates  in  vigorous  action 
are  brought  into  contact.  The  spark  is  occasioned  by  the  passage 
of  electricity  across  a thin  stratum  of  air,  and,  therefore,  its  produc- 
tion proves  that  electro-motion  really  occurred  while  the  wires  were 
yet  separated  by  a thin  stratum  of  air,  which  permitted  the  electric 
current  to  pass,  and  anterior  to  their  actual  contact.  This  current 
in  Faraday’s  experiment,  was  so  feeble  compared  with  the  one 
excited  by  the  acid  solution,  that  its  influence  was  scarcely  ap- 


Fig.  7 


M 


Fig.  77. 


preciable  ; but  if  the  opposed  currents  had 
been  of  the  same  force,  no  action  would 
have  ensued.  To  illustrate  this  still  fur- 
ther, Faraday  fixed  a plate  of  platinum,  r, 

(Fig.  76)  parallel  and  near  to  a plate  of  amal-  y z 

gamated  zinc,  z.  On  placing  a drop  of  dilute  sulphuric  acid  at  y, 
and  making  metallic  contact  between  the  plate  at  z p,  a positive  elec- 
tric current  flowed  in  the  direction  of  the  arrows.  If,  in  the  same 
plates  (Fig.  77),  the  acid  be  introduced  at  x, 
and  metallic  contact  be  made  at  p z,  the  cur- 
rent, passing  as  before  from  zinc  through 
the  liquid  to  the  platinum,  has  a direction  op- 
posed to  that  of  Fig.  59,  owing  to  the  reversed 
position  of  the  acid.  If,  then,  in  the  same  plate,  (Fig.  78),  a drop  of 
acid  be  introduced  at  y and  x,  the  conditions  are  obviously  fulfilled  for 
producing  two  opposite  currents  of  positive  electricity  , each  fluid  act- 
ing as  a substitute  for  metallic  contact  in  conducting  the  current  which 
the  other  tends  to  generate.  If  these  opposing  currents  happen  to  be 
equal,  they  will  annihilate  the  effects  each  separately  would  produce  ; 


* The  Philosophical  Transactions  contain  a succession  of  essays  on  voltaic  electri- 
city from  the  pen  of  Faraday,  in  which  numerous  errors  have  been  exposed  and  new 
views  of  deep  interest  established. 


94 


Chap.  I. 


Theory  of 
compound 
circles. 


Quantity 
and  intensi- 
ty. 


Energy  es- 
timated. 


Nature  of 
electricity. 


Electricity — Voltaic. 


Fig.  78. 

P 


X 


x 


and  if  unequal,  the  stronger  current,  as  in  Fig.  75,  will  annihilate 
the  weaker,  and,  though  with  diminished  power,  impress  its  charac- 
ter on  the  circuit. 

301.  These  considerations,  made  in  reference  to  a simple  circle, 
lead  at  once  to  the  theory  of  the  compound  circle.  For  if,  in  Fig* 
78,  a drop  of  dilute  acid,  which  acts  solely  on 
the  zinc,  be  introduced  at  y,  and  a different 
liquid  at  z , capable  of  corroding  platinum  and 
not  zinc,  then  the  chemical  action  at  y will 
cause  a positive  current  from  zinc  to  platinum, 
and  that  at  z a similar  current  from  platinum  to  zinc.  The  two  cur- 
rents tend  to  circulate  in  the  same  direction,  and  each  promotes  the 
progress  of  the  other.  The  same  state  of  things  exists  in  the  batte- 
ries represented  by  Figs.  66  and  68.  Chemical  action  taking  place 
on  the  zinc  of  each  pair  of  plates,  there  is  a tendency  to  establish  an 
equal  number  of  positive  currents  all  in  the  same  direction  ; and  the 
simultaneous  effort  of  all  urges  on  the  current  with  a force  which  it 
could  not  derive  from  a single  pair  of  plates.  It  is  now,  also,  appa- 
rent that  all  the  zinc  plates  should  have  their  surfaces  towards  one 
side,  and  those  of  copper  towards  the  other : one  reversed  pair  tends 
to  establish  a counter-current,  which  enfeebles  the  influence  of  the 
rest.  On  the  same  principle,  the  exciting  liquid  of  a voltaic  circle 
should  act  exclusively  on  one  of  the  plates  : if  the  copper  is  oxidized 
as  fast  as  the  zinc,  opposite  currents  will  be  excited,  which  more  or 
less  completely  counteract  each  other.  For  this  reason,  platinum  and 
zinc  act  better  than  copper  and  zinc,  especially  when  nitric  acid  is 
employed. 

302.  Electricians  distinguish  between  quantity  and  intensity  in 
galvanism  as  in  ordinary  electricity.  Quantity , in  reference  to  a 
voltaic  circle,  signifies  the  quantity  of  electric  fluid  set  in  motion  ; 
and  by  tension  or  intensity  is  meant  the  energy  or  effort  with  which 
a current  is  impelled.  The  current  of  a single  pair  of  plates,  though 
variable  in  intensity  according  as  the  nature  and  strength  of  the  ex- 
citing liquid  varies,  never  attains  a high  tension.  A compound 
circle  dees  not  act  by  directly  increasing  the  quantity  of  electricity, 
but  by  giving  impetus  or  tension  to  that  which  is  excited. 

303.  The  energy  of  a voltaic  circle  is  usually  estimated  either  by 
the  deflection  which  it  causes  on  a magnetic  needle,  or  by  its  power 
of  chemical  decomposition. 

Chemical  decomposition  depends  on  quantity  and  intensity  to- 
gether, and  affords  a criterion  of  the  increased  tension  of  a com- 
pound circle  due  to  an  increase  in  the  number  of  its  plates. 

304.  Some  conceive  that  what  is  called  an  electric  current  is  not 
an  actual  transfer  of  anything,  but  a process  of  induction  among  the 
molecules  of  a conductor  passing  progressively  along  it.  Others, 
denying  independent  materiality  to  electricity,  may  ascribe  it  to  a 
wave  of  vibrating  matter,  just  as  the  phenomena  of  optics  are  ex- 
plained by  the  undulatory  theory.  But  whatever  theory  of  the  na- 
ture of  electricity  may  be  adopted,  it  seems  necessary,  after  the  ex- 
periments of  Faraday  on  the  identity  of  voltaic  and  common  electrici- 
ty, that  the  nature  of  an  electric  and  voltaic  current  is  essentially  the 
same. 


95 


Identity  of  Galvanism  and  Electricity. 

305.  When  a zinc  and  copper  plate  are  immersed  in  dilute  acid,  Sect,  v. 

and  the  wire  attached  to  the  former  is  connected  with  a gold-leaf 
electrometer  of  sufficient  delicacy,  the  leaves  diverge  with  negative  ga^anism 
electricity ; and  on  testing  the  wire  of  the  copper  plate  in  a smaller  on  electro-, 
manner,  divergence  from  positive  electricity  is  obtained.  The  effect m#ter- 

is  so  feeble  with  a single  pair  of  plates,  as  to  be  scarcely  apprecia- 
ble ; but  with  a battery  of  many  pairs  it  is  very  distinct,  though  nev- 
er powerful.  The  condition  of  a battery  which  gives  the  greatest 
divergency  to  an  electrometer  is  that  of  numerous  plates ; small 
plates  an  inch  square  being  just  as  effectual  as  large  ones, 

306.  A Leyden  jar  may  be  charged  from  either  wire  of  an  un-  Leyden  jar 
broken  circuit,  provided  the  battery  be  in  a state  to  supply  a large  charged  ; 
quantity  of  electricity  of  high  tension,  as  when  formed  of  numerous 
four-inch  plates  excited  by  dilute  acid.  When  the  wires  from  such  shock. 

a battery  are  brought  near  each  other,  a spark  is  seen  to  pass  be- 
tween them ; and  on  establishing  the  communication  by  means  of 
the  hands,  previously  moistened,  a distinct  shock  is  perceived.  On 
sending  the  current  through  fine  metallic  wires  or  slender  pieces  of 
plumbago  or  compact  charcoal,  these  conductors  become  intensely 
heated,  the  wires  even  of  the  most  refractory  metals  are  fused,  and 
a vivid  white  light  appears  at  the  points  of  the  charcoal.  If  the  com-  ETect  on 
munication  be  established  by  metallic  leaves,  the  metals  burn  with  metais> 
vivid  scintillations.  Gold-leaf  burns  with  a white  light,  tinged  with 
blue,  and  yields  a dark  brown  oxide  ; and  the  light  emitted  by  silver 
is  exceedingly  brilliant,  and  of  an  emerald-green  colour.  Copper 
emits  a bluish-white  light  attended  with  red  sparks,  lead  a beauti- 
ful purple  light,  and  zinc  a brilliant  white  light  inclining  to  blue,  and 
fringed  with  red.  (Singer.) 

307.  The  phenomena  seem  to  arise  from  the  current  passing  Explained, 
along  these  substances  with  difficulty ; a circumstance  which,  as 

they  are  perfect  conductors,  can  only  happen  when  the  quantity  to 
be  transmitted  is  out  of  proportion  to  the  extent  of  surface  over 
which  it  has  to  pass.  It  is,  therefore,  an  object  to  excite  as  large  a 
quantity  of  electricity  in  a given  time  as  possible,  and  for  this  pur- 
pose a few  large  plates  answer  better  than  a great  many  small  ones. 

A strong  acid  solution  should  also  be  used  ; since  energetic  action, 
though  of  short  continuance,  is  more  important  than  a moderate  one 
of  greater  permanence.  A mixture  of  ten  or  twelve  parts  of  water 
to  one  of  nitric  acid  is  applicable ; or,  for  the  sake  of  economy,  a 
mixture  of  one  part  of  nitric  to  two  parts  of  sulphuric  acid  may  be 
substituted  for  pure  nitric  acid. 

308.  Most  of  the  effects  of  galvanism  are  so  similar  to  those  of  the  identity  of 
electrical  machine,  that  it  is  impossible  to  witness  and  compare  both  galvanism 
series  of  phenomena  without  ascribing  them  to  the  same  agent.  ^"td  electn‘ 
The  question  of  identity  early  occupied  the  attention  of  Wollaston, 

who  made  some  very  beautiful  and  conclusive  experiments  to  prove 
that  the  chemical  effects  of  galvanism  may  be  characteristically  pro- 
duced by  a current  from  the  electrical  machine.^  The  subject  has 
been  examined  anew  by  Faraday,  who  has  subjected  the  effects  of 
electricity  and  galvanism  to  a minute  and  critical  comparison : he 
has  obtained  ample  proof  of  the  decomposing  power  of  an  electric 


* Phil.  Trans.  1801. 


96 


Chap.  I. 


Chemical 
action  of 
galvanism. 

Water  de- 
composed. 


Other  com- 
pounds. 


Davy's  ex- 
periments. 


Electricity — Voltaic. 

current  from  an  electrical  machine,  both  by  repeating  the  experi- 
ments of  Wollaston  and  devising  new  ones  of  his  own.  These  re- 
searches have  led  to  a remarkable  contrast  between  the  quantity  of 
electricity  concerned  in  the  production  of  voltaic  and  ordinary  elec- 
trical phenomena.  Faraday  states,  that  the  quantity  of  electric  fluid 
employed  in  decomposing  a single  grain  of  water  is  equal  to  that  of 
a very  powerful  flash  of  lightning. 

309.  The  chemical  agency  of  the  voltaic  apparatus,  to  which 
chemists  are  indebted  for  their  most  powerful  instrument  of  analysis, 
was  discovered  by  Carlisle  and  Nicholson.  The  substance  first  de- 
composed by  it  was  water.  When  two  gold  or  platinum  wires  are 
connected  with  the  opposite  ends  of  a battery,  and  their  free  extremi- 
ties are  plunged  into  the  same  portion  of  water,  (Fig.  79,*)  but  with- 
out touching  each  other,  hydrogen  gas  is  disengaged  at  the  nega- 
tive and  oxygen  at  the  positive  wire.  By  collecting  the  gases  in 
separate  tubes  as  they  escape,  (Fig.  Sit)  they  are  found  to  be  quite 
pure,  and  in  the  exact  ratio  of  two  measures  of  hydrogen  to  one  of 
oxygen.  When  wires  of  a more  oxidable  metal  are  employed,  the 
result  is  somewhat  different.  The  hydrogen  gas  appears  as  usual 
at  the  negative  wire ; but  the  oxygen,  instead  of  escaping,  combines 
with  the  metal,  and  converts  it  into  an  oxide. 

310.  This  important  discovery  led  many  able  experimenters  to 
make  similar  trials.  Other  compound  bodies,  such  as  acids  and 
salts,  were  exposed  to  the  action  of  galvanism,  and  all  of  them  were 
decomposed  without  exception,  one  of  their  elements  appearing  at 
one  side  of  the  battery,  and  the  other  at  its  opposite  extremity.  An 
exact  uniformity  in  the  circumstances  attending  the  decomposition 
was  also  remarked.  Thus,  in  decomposing  water  or  other  com- 
pounds, the  same  kind  of  body  was  always  disengaged  at  the  same 
side  of  the  battery.  The  metals,  inflammable  substances  in  general, 
the  alkalies,  earths,  and  the  oxides  of  the  common  metals,  were 
found  at  the  negative  wire  ; while  oxygen,  chlorine,  and  the  acids, 
went  over  to  the  positive  surface. 

311.  Davy  observed  that  if  the  conducting  wires  were  plunged 
into  separate  vessels  of  water,  made  to  communicate  by  some  moist 
fibres  of  cotton  or  amianthus,  the  two  gases  were  still  disengaged  in 


* Fig.  79.  Shows  the  method  of  decomposing  water  in  a glass  tube.  + Fig  81. 
Apparatus  for  collecting  the  gases  in  separate  tubes ; the  tubes  h o , are  filled  with 
Fig. 79.  Fig.  80.  Fig.  81 


water,  and  inverted  in  the  globular  vessel  d}  also  containing  water ; the  tubes  pass 
through  holes  in  a wooden  cover  ; n p,  are  platinum  wires  passing  through  the  globe 
to  connect  with  the  voltaic  apparatus.  Fig.  80.  Similar  arrangement  for  collecting 
the  mixed  gases. 


97 


Faraday's  Researches . 

their  usual  order,  the  hydrogen  in  one  vessel,  and  the  oxygen  in  the  sect,  v. 
other,  just  as  if  the  wires  had  been  immersed  into  the  same  portion 
of  that  liquid.  This  singular  fact,  and  another  of  the  like  kind  ob- 
served by  Hisinger  and  Berzelius,  induced  him  to  operate  in  the 
same  way  with  other  compounds,  and  thus  gave  rise  to  his  celebra- 
ted researches  on  the  transfer  of  chemical  substances  from  one  ves- 
sel to  another.^ 

In  these  experiments  two  agate  cups,  n and  p,  were  cm-  Fjg.  g2.  Exp. 

ployed,  the  first  communicating  with  the  negative,  the  second 
with  the  positive  wire  of  the  battery,  and  connected  together 
by  moistened  amianthus.  On  putting  a solution  of  sulphate  of 
potassa  or  soda  into  n,  and  distilled  water  into  p,  the  acid 
very  soon  passed  over  to  the  latter,  while  the  liquid  in  the 
former,  which  was  at  first  neutral,  became  distinctly  alkaline. 

The  process  was  reversed  by  placing  the  saline  solution  in  p,  and  the  distilled 
water  in  ra,  when  the  alkali  went  over  to  the  negative  cup,  leaving  free  acid  in 
the  other. 

That  t.he  acid  in  the  first  experiment,  and  the  alkaline  base  in 
the  second,  actually  passed  along  the  amianthus,  was  obvious ; for 
on  one  occasion,  when  nitrate  of  oxide  of  silver  was  substituted  for 
the  sulphate  of  potassa,  the  amianthus  leading  to  n was  coated  with 
a film  of  metal.  A similar  transfer  was  effected  by  putting  distil- 
led water  into  n and  p , and  a saline  solution  in  a third  cup  placed 
between  the  two  others,  and  connected  with  each  by  moistened  ami- 
anthus. In  a short  time  the  acid  of  the  salt  appeared  in  p , and  the 
alkali  in  n.  It  was  in  pursuing  these  researches  that  Davy  made 
his  great  discovery  of  the  decomposition  of  the  alkalies  and  earths, 
which  till  then  had  been  regarded  as  elementary.!  I 

312.  Such  is  a statement  of  the  principal  phenomena  of  electro- 
chemical decomposition  according  to  the  earlier  experiments.  The 
facts  then  observed  were  received  as  established  truths  of  science. 

But  Faraday,  in  his  revision  of  this  part  of  the  science,  has  not 
only  added  much  new  matter,  but  proved  that  several  points,  which  Faraday’s 
were  considered  as  fundamental  maxims,  are  erroneous.  Before  de-  researches, 
scribing  his  results,  however,  it  is  necessary  to  define  the  new  terms 
which  he  has  had  occasion  to  introduce.  In  order  to  decompose  a 
compound,  it  is  necessary  that  it  should  be  liquid,  and  that  an  elec- 
tric current  should  pass  through  it,  an  object  easily  effected  by  dip- 


* Phil.  Trans.  1807.  + Ibib.  1808. 


t The  transfer  of  acid  and  alkali  may  be  shown  by  the  fol-  Fig-  83- 

lowing  arrangement:  Fill  the  glass  tubes  a a,  Fig-  83, 
which  are  closed  at  top  and  open  at  bottom,  with  infusion 
of  violets,  or  purple  cabbage,  and  invert  them  in  the  basins 
b b,  containing  a solution  of  Glauber’s  salt,  and  connected 
by  the  glass  tube  c,  also  containing  the  solution  ; p and 
n are  platinum  wires,  which  pass  into  the  tubes  nearly  to 
the  bottom,  and  which  are  to  be  connected  with  the  positive 
and  negative  extremities  of  the  Voltaic  apparatus.  It  will 
be  found  that  oxygen  is  evolved  at  the  wire/),  and  hydrogen 
at  n,  derived  from  the  decomposition  of  the  water.  The 
Glauber’s  salt,  which  consists  of  sulphuric  acid  and  soda, 
will  also  be  decomposed:  and  the  blue  liquor  will  be  ren- 
dered red  in  the  positive  vessel,  by  the  accumulation  of  sul- 
phuric acid,  and  green  in  the  negative,  by  the  soda,  while 
the  acid  and  alkali  will  each  traverse  the  tube  c without 
uniting,  in  consequence  of  being  under  the  influence  of  electrical  attraction. 

13 


A 


Traniferof  acid 
and  alkali. 


98 


Chap.  I. 


New  terms, 


Anode  and 
Cathode. 


Electro- 

lyze. 


Anions. 


Cations. 


Faraday’s 

results. 

All  com 
pounds  not 
electro- 
lytes. 


Secondary 

action. 


Electricity — Voltaic. 

ping  into  the  liquid  the  ends  of  the  metallic  wires  which  communi- 
cate with  the  voltaic  circle.  These  extremities  of  the  wires  are 
commonly  termed  poles,  from  a notion  of  their  exerting  attractive 
and  repulsive  energies  towards  the  elements  of  the  decomposing 
liquid,  just  as  the  poles  of  a magnet  act  towards  iron;  and  each  is 
further  distinguished  by  the  term  positive  or  negative,  according  as 
it  affects  an  electrometer  with  positive  or  negative  electricity.  Fara- 
day contends  that  these  poles  have  not  any  attractive  or  repulsive 
energy,  and  act  simply  as  a path  or  door  to  the  current  : he  hence 
calls  them  electrodes , from  vUxtqov,  and  dSog , a way.  The  electrodes 
are  the  surfaces,  whether  of  air,  water,  metal,  or  any  other  sub- 
stance, which  serve  to  convey  an  electric  current  into  and  from  the 
liquid  to  be  decomposed.  The  surfaces  of  this  liquid  which  are  in 
immediate  contact  with  the  electrodes,  and  where  the  elements  make 
their  appearance,  are  termed  anode  and  cathode  from  dva,  upwards, 
and  ddog,  the  way  in  which  the  sun  rises,  and  xara,  downwards , the 
way  in  which  the  sun  sets.  The  anode  is  where  the  positive  cur- 
rent is  supposed  to  enter,  and  the  cathode  where  it  quits,  the  de- 
composing liquid,  its  direction,  when  the  electrodes  are  placed  east 
and  west,  corresponding  with  that  of  the  positive  current  which  is 
thought  to  circulate  on  the  surface  of  the  earth.  To  electrolyze  a 
compound,  is  to  decompose  it  by  the  direct  action  of  galvanism,  its 
name  being  formed  from  nlenTQov  and  Xvo),  to  unloose,  or  set  free  ; 
and  an  electrolyte  is  a compound  which  may  be  electrolyzed.  The 
elements  of  an  electrolyte  are  called  ions,  from  iov,  going,  neuter 
participle  of  the  verb  to  go.  Anions  are  the  ions  which  appear  at 
the  anode,  and  are  usually  termed  the  electro-negative  ingredients 
of  a compound,  such  as  oxygen,  chlorine,  and  acids ; and  the  electro- 
positive substances,  hydrogen,  metals,  alkalies,  which  appear  at  the 
cathode,  are  cations.  Whatever  may  be  thought  of  the  necessity 
for  some  of  these  terms,  the  words  electrode,  electrolyze,  and  electro- 
lyte, are  peculiarly  appropriate. 

313.  The  principal  facts  determined  by  Faraday,  may  be  arrang- 
ed under  the  following  propositions  : — 

1.  All  compounds,  contrary  to  what  has  been  hitherto  supposed, 
are  not  electrolytes,  that  is,  are  not  directly  decomposable  by  an 
electric  current.  But  in  making  this  assertion  it  is  necessary  to 
distinguish  between  primary  and  secondary  decomposition.  Thus 
water  is  an  electrolyte,  its  hydrogen  being  delivered  up  at  the  nega- 
tive and  its  oxygen  at  the  positive  electrode.  Nitric  acid  is  not  an 
electrolyte,  on  subjecting  it  to  voltaic  action,  the  water  of  the  solution 
is  electrolyzed,  and  its  hydrogen  arriving  at  the  negative  electrode 
decomposes  the  nitric  acid,  water  being  there  reproduced  and  ni- 
trous acid  formed.  Very  numerous  secondary  actions  are  occasion- 
ed in  this  way,  because  the  disunited  elements  are  presented  in  a 
nascent  form,  which  is  peculiarly  favourable  to  chemical  action.  By 
slow  secondary  actions,  effected  by  very  feeble  currents,  Becquerel, 
Crosse,  and  others,  have  procured  several  crystalline  compounds  ana- 
logous to  minerals.* 

2.  Most  of  the  salts  which  have  been  examined  are  resolvable  into 


* See  notice  of  Crosse’s  experiments  in  Sixth  Report  of  British  Association , p.  47. 


99 


Faradaxfs  Results. 

acid  and  oxide,  apparently  without  reference  to  their  proportions.  Sect,  v. 
But  in  compounds  of  two  elements,  the  ratio  of  combination  has  an 
influence  which  has  hitherto  been  wholly  overlooked.  No  two  ele- 
ments appear  capable  of  forming  more  than  one  electrolyte.  Sub- 
stances which  consist  of  a single  equivalent  of  one  element  and  two 
or  more  equivalents  of  some  other  element,  are  not  electrolytes: 
this  is  the  reason  why  sulphuric  and  nitric  acid  and  ammonia  do 
not  yield  primarily  to  voltaic  action.  This  principle  bids  fair  to  be- 
come very  important  in  determining  which  of  several  compounds  of 
two  elements  contain  single  equivalents,  (116  note.)  Water,  which 
is  remarkable  for  its  easy  decomposition,  may  hence  be  inferred  to 
be  a true  binary  compound. 

3.  It  has  been  ascertained  that  most  of  the  elements  are  ions , and  Most  ele- 
it  is  probable  that  all  of  them  are  so  ; but  there  are  several  which are 
have  not  yet  been  proved  to  be  so. 

4.  A single  ion , that  is,  one  ion  not  in  combination  with  another,  Character 
has  no  tendency  to  pass  to  either  of  the  electrodes,  and  is  quite  in*  iytic  action, 
different  to  the  passing  current,  unless  it  be  itself  a compound  ion , 

and  therefore  electrolyzable.  The  character  of  true  electrolytic  ac- 
tion consists  in  the  separation  of  ions , one  passing  to  one  electrode 
and  another  to  the  opposite  electrode,  and  appearing  there  at  the 
same  instant,  unless  the  appearance  of  one  or  both  be  prevented  by 
some  secondary  action. 

5.  There  is  no  such  thing  as  a transfer  of  ions  in  the  sense  usual-  No  transfer 
ly  understood.  In  order  that  the  elements  of  decomposed  water oflons* 
should  appear  at  the  opposite  electrodes,  there  must  be  water  be- 
tween the  electrodes  ; and  for  the  similar  separation  of  sulphuric 

acid  and  soda,  there  must  be  a line  of  particles  of  sulphate  of  soda 
extending  from  one  electrode  to  the  other. 

6.  Faraday  has  proved  that  even  air  may  serve  as  an  electrode.  Air  may  be 
A current  from  the  prime  conductor  of  an  electrical  machine  was  ®r”^ec" 
made  to  pass  from  a needle’s  point  through  air  to  a pointed  piece  of  ro  e” 
litmus  paper  moistened  with  sulphate  of  soda,  and  then  to  issue 

from  a similarly  moistened  point  of  turmeric  paper.  True  electroly- 
tic action  took  place,  the  litmus  becoming  red  and  the  turmeric  paper 
brown,  though  both  extremities  of  the  decomposing  solution  commu- 
nicated solely  with  a stratum  of  air. 

7.  Electro-chemical  decomposition  cannot  occur  unless  an  elec-  Electro- 
trie  current  is  actually  transmitted  through  it ; or,  in  other  terms,  an 
electrolyte  is  always  a conductor  of  electricity.  Water,  which  con- 
ducts an  electric  current,  ceases  to  do  so  when  it  passes  into  ice,  and 

then  also  resists  decomposition — an  observation  equally  true  of  all 
electrolytes  in  becoming  solid. 

8.  Chemical  compounds  differ  in  the  electrical  force  required  for  Force  re- 

j * quired  to 

decomposition.  . , . , „ , decompose. 

9.  The  conduction  of  the  electric  currents  within  the  cells  of  a Electro. 
voltaic  circle  depends  on  chemical  decomposition  equally  with  that  lytes  only, 
between  platinum  electrodes.  No  substance  not  an  electrolyte  can  exclte- 
serve  to  excite  a voltaic  apparatus,  and  for  the  passage  of  electricity 

from  plate  to  plate  through  the  intervening  solution,  the  separation 
of  substances  previously  combined  in  the  required  ratio  is  essential. 

314.  In  experiments  on  decomposition  the  course  of  the  electricity  stances"to 
should  be  facilitated  by  employing  large  electrodes  and  wires,  and  be  regarded 


100 


Electricity — Voltaic. 


Chap.  I. 

in  experi- 
ments on 
decomposi- 
tion. 


Electro- 

chemical 

equiva- 

lents. 


Quantity  of 

electricity 

estimated- 


Exciting  liquid. 


Volumeter.  ] 


placing  them  at  a short  distance  from  each  other  in  a good  conduct- 
ing solution.  It  is  important,  also,  that  all  the  cells  of  a circle  be 
excited  with  a liquid  of  the  same  strength.* 

315.  In  a voltaic  circle  in  which  no  zinc  is  oxidized  but  what  con- 
tributes to  excite  an  electric  current,  the  quantity  of  zinc  dissolved  in 
a given  time  from  each  plate  is  in  a constant  ratio,  not  only  to  the  hy- 
drogen gas  evolved  from  the  corresponding  copper  plate,  but  to  the  hy- 
drogen set  free  at  the  negative  electrode.  The  ratio  is  such,  that  32.3 
parts  of  zinc  are  dissolved  during  the  evolution  of  1 part  of  hydrogen 
gas  ; and  the  conclusion  which  Faraday  has  drawn  from  this  and 
numerous  similar  experiments  is,  that  the  quantity  of  electricity  set 
in  motion  by  the  oxidation  of  32.3  grains  of  zinc  exactly  suffices  for 
resolving  9 grains  of  water  into  its  elements.  If  the  same  current, 
by  means  of  4 pairs  of  electrodes,  be  made  to  decompose  water,  chlo- 
ride of  silver,  chloride  of  lead,  and  chloride  of  tin,  all  in  the  liquid 
state,  the  quantities  of  hydrogen,  silver,  lead,  and  tin  eliminated  at 
the  4 negative  electrodes  will  be  in  the  ratio  of  1,  108,  103.6,  and 
57.9  ; while,  at  one  positive  electrode,  oxygen,  and  at  the  three 
others  chlorine,  in  the  ratio  of  8 to  35.4,  are  separated.  It  thus  dis- 
tinctly appears — and  it  is  a new  and  important  discovery — that  elec- 
tro-chemical decomposition  is  perfectly  definite,  a given  quantity  of 
electricity  evolving  the  ingredients  of  compound  bodies  in  well  de- 
fined and  invariable  proportions,  to  which  Faraday  has  given  the 
name  of  electro-chemical  equivalents.  The  reader  will  at  once  see 
that  these  numbers  are  identical  with  the  chemical  equivalents  (see 
table).  Another  connexion,  then,  closer  than  any  before  traced,  is 
established  between  electricity  and  chemical  attraction,  showing  a 
mutual  dependence  and  similarity  of  effect  between  two  agencies, 
such  as  almost  forces  a belief  in  their  identity.  T.  106. 

316.  The  definite  nature  of  electro-chemical  action,  suggested  to 
Faraday  a ready  mode  of  estimating  the  quantity  of  electricity  circu- 
lating in  a voltaic  apparatus.  The  instrument  is  contrived  to  collect 
the  gases  evolved  from  acidulated  water  during  a given  interval, 
in  a tube  divided  into  equal  measures,  which  then  expresses  de- 
grees of  electricity,  just  as  the  expansion  of  a liquid  in  a thermom- 
eter indicates  degrees  of  temperature.  The  instrument,  as  con- 
structed for  this  object,  is  called  by  Faraday  a volta-electrometer. 
Various  forms  of  it  have  been  described  by  him,  according  as  it  is 
wished  to  collect  oxygen  or  hydrogen  separately  or  both  logether.t 

* A mixture  of  a proper  strength  for  galvanic  troughs,  is  obtained  by  adding  two 
parts  in  bulk  of  oil  of  vitriol  and  one  part  of  common  nitric  acid  to 
100  parts  of  water,  the  whole  being  well  stirred  together  until  well 
mixed.  Its  power  should  be  tested  before  it  is  poured  into  the 
troughs,  by  dipping  a clean  piece  of  zinc  into  a little  of  it  in  a glass, 
and  observing  the  degree  of  action.  A stream  of  bubbles  should 
he  disengaged,  so  small  that  their  size  can  hardly  be  determined  by 
the  naked  eye.  If  the  action  be  strong,  and  bubbles  of  a considera- 
ble size  are  evolved,  more  water  should  be  added.  For  full  direc- 
tions for  operating  with  voltaic  apparatus,  see  Faraday’s  Chem. 

Manip.  445. 

+ See  Faraday’s  papers  in  Philos.  Trans,  (seventh  series),  1834, 
p.  86.  One  of  the  most  convenient  forms  is  represented  by  Fig.  84. 

It  is  composed  of  three  pieces,  a wooden  support,  a glass  tube, 
and  chamber.  The  two  latter  are  fitted  with  brass  collars  screw- 
ing into  each  other.  The  tube  is  13|  inches  long,  and  5-6ths  of  an 
inch  in  diameter,  open  at  bottom,  closed  at  top,  and  divided  into  cu- 
bic inches  and  parts.  The  chamber  is  4*  inches  in  diameter  at  the 


101 


Faraday's  Theory. 

317.  The  most  celebrated  attempt  to  explain  the  phenomena  of  sect,  v. 
galvanism,  was  made  by  Davy  in  his  essay  on  Some  Chemical  Agen-  Theories  of 
cies  of  Electricity  {Phil.  Trans.  1807),  by  means  of  an  hypothesis  electro- 
which  has  received  the  appellation  of  the  electro-chemical  theory.  He  jecomposi- 
considered  that  a certain  electric  condition,  either  positive  or  nega-  tion, 
tive,  is  natural  to  the  atoms  or  combining  molecules  of  bodies  ; that 
chemical  union  is  the  result  of  electrical  attraction  taking  place  be- 
tween oppositely  excited  atoms,  and  that  ordinary  chemical  decom- 
position arises  from  two  combined  atoms  being  drawn  asunder  by  the 
electric  energies  of  other  atoms  more  potent  than  those  by  which 

they  were  united.  Davy  regarded  the  metallic  terminations  or  poles  Davy’s> 
of  a voltaic  circle  as  two  centres  of  electrical  power,  each  acting  re- 
pulsively to  particles  in  the  same  electric  state  as  itself,  and  by  at- 
traction on  those  which  were  oppositely  excited.  The  necessary 
result  was,  that  if  the  electric  energy  of  the  battery  exceeded  that  by 
which  the  elements  of  any  compound  subject  to  its  action  were  held 
together,  decomposition  followed,  and  each  element  was  transferred 
bodily  to  the  pole  by  which  it  was  attracted.  Substances  which  ap- 
peared at  the  positive  pole*  such  as  oxygen,  chlorine,  and  acids,  were 
termed  electro-negative  substances  ; and  those  electropositive  bodies, 
which  were  separated  at  the  negative  pole. 

318.  Faraday  contends  that,  between  the  electrodes  and  acting  in  Faraday’s, 
right  lines,  there  is  an  axis  of  power  which  urges  the  electro-negative 
element  of  an  electrolyte  in  the  direction  the  positive  current  moves, 

and  gives  an  opposite  impulse  to  the  electro-positive  element.  He 
adopts  the  opinion  of  Grotthuss,  that  the  decomposing  influence  is 
not  exerted  on  any  single  particle  of  the  electrolyte,  but  that  rows  of 
particles  lying  between  the  electrodes  are  equally  subject  to  its  ac- 
tion. When  a particle  of  oxygen  is  evolved  at  the  positive  electrode, 
the  hydrogen  with  which  it  had  been  combined  unites  with  the  oxy- 
gen of  a contiguous  particle  of  water,  on  the  side  towards  which  the 
positive  current  is  moving ; the  second  particle  of  hydrogen  decom- 
poses a portion  of  water  still  nearer  to  the  negative  electrode ; and 
the  same  process  of  decomposition  and  reproduction  of  water  con- 
tinues until  it  reaches  the  water  in  immediate  contact  with  the  nega- 
tive electrode,  the  hydrogen  of  which  is  disengaged.  This  operation, 
described  as  commencing  at  one  electrode,  takes  place  simultane- 
ously at  both : a row  of  particles  of  oxygen  suddenly  lose  their 
affinity  for  the  hydrogen  situated  on  the  side  next  the  negative  elec- 
trode, in  favour  of  those  respectively  adjacent  to  each  on  the  other 
side  ; while  the  affinity  of  a similar  row  of  particles  of  hydrogen  is 
diminished  for  the  oxygen  on  the  side  of  the  positive  electrode,  and  is 


base  and  in  height.  Through  a short  cylinder  of  wood,  cemented  into  the  bottom  of 
the  chamber,  pass  two  platinum  wires,  prolonged  by  larger  wires  that  dip  into  a small 
quantity  of  quicksilver  in  a cavity  in  the  centre  of  the  wooden  support ; the  cavity  is 
divided  by  a partition,  and  each  wire  communicates  with  a separate  portion  of  the  quick- 
silver: wires  pass  to  small  brass  cups,  on  the  support,  to  contain  quicksilver;  thus  the 
connexion  with  any  apparatus  is  readily  made.  When  prepared  for  use,  the  chamber  is 
to  be  filled  to  about  three  fourths  with  dilute  sulphuric  acid  of  specific  gravity  1 .336,  or 
from  that  to  specific  gravity  1.25.  The  tube  is  then  filled  with  the  same  liquid,  and  a 
piece  of  clean  paper  of  a size  to  cover  the  open  end,  is  pressed  upon  it.  The  tube  can 
now  be  inverted  and  introduced,  the  paper  withdrawn  by  a glass  rod,  and  the  tube 
screwed  on.  The  connexion  is  now  made,  the  evolved  gases  rise  to  the  upper  part  of 
the  tube,  and  their  volumes  are  ascertained  by  inspection.  This  form  of  the  appara- 
tus is  an  improvement  on  that  of  Fig.  9,  in  the  paper  above  referred  to. 


102 


Nomenclature. 


Chap  II. 


Magnetic 
effects  of 
galvanism. 


Old  names. 


increased  for  those  on  their  opposite  side.  Hence,  for  the  elimina- 
tion of  the  elements  of  an  electrolyte  at  the  electrode,  it  is  essential 
that  the  electrolyte  itself  should  occupy  the  space  between  the  elec- 
trodes, and  be  in  contact  with  them.  The  theory,  however,  is  at 
present  incomplete. 

319.  The  power  of  lightning  in  destroying  and  reversing  the 
poles  of  a magnet,  and  in  communicating  magnetic  properties  to 
pieces  of  iron  which  did  not  previously  possess  them,  was  noticed  at 
an  early  period  of  the  science  of  electricity,  and  led  to  the  supposi- 
tion that  similar  effects  may  be  produced  by  the  common  electrical 
and  voltaic  apparatus.  Attempts  were  made  to  communicate  the 
magnetic  virtue  by  means  of  electricity  and  galvanism  ; but  no  re- 
sults of  importance  were  obtained  till  the  winter  of  1819,  when 
Oersted  of  Copenhagen  made  his  famous  discovery,  which  forms  the 
basis  of  a new  branch  of  science.* 

The  fact  observed  by  Oersted  was,  that  the  metallic  wire  of  a 
closed  voltaic  circle,  and  the  same  is  true  of  charcoal,  saline  fluids, 
and  any  conducting  medium  which  forms  part  of  a closed  circle, 
causes  a magnetic  needle  placed  near  it  to  deviate  from  its  natural 
position,  and  assume  a new  one,  the  direction  of  which  depends  upon 
the  relative  position  of  the  needle  and  the  wire.t 

320.  In  1832  Forbes  succeeded  in  obtaining  a spark  from  a magnet 
without  the  aid  of  galvanism,  and  various  methods  have  since  been  con- 
trived. By  causing  the  armature  of  soft  iron  to  revolve  with  rapidity 
in  front  of  the  poles  of  a powerful  magnet,  very  remarkable  results 
have  been  obtained.  The  voltaic  currents  are  induced  in  one  direc- 
tion as  the  armature  approaches  the  magnetic  poles,  and  are  reversed 
a?  it  quits  them  ; so  that  the  currents  change  their  direction  twice  in 
each  revolution.  On  all  these  occasions  the  source  of  the  electricity 
is  the  same,  being  always  induced  in  the  silked  wire  or  helix  with 
which  the  armature  is  covered;  it  has  all  the  characters  of  a voltaic 
current.  It  produces  brilliant  sparks,  renders  platinum  wire  red  hot, 
and  gives  a strong  shock.  It  readily  explodes  gunpowder,  and  a 
mixture  of  oxygen  and  hydrogen  gases.  It  decomposes  water  ra- 
pidly; and  though  from  the  rapid  reversal  in  the  direction  of  the 
currents,  both  gases  are  given  off  at  the  same  wire,  Pixii  succeeded 
in  collecting  them  separately. $ (An.  de  Ch.  et  de  Ph.  li.  72.) 


CHAPTER  II. 

Section  I.  Nomenclature. 

321.  The  names  formerly  applied  to  chemical  substances,  were 
often  fanciful  and  even  absurd,  but  in  17S7  a new  nomenclature  was 
framed  by  the  celebrated  French  chemists  Lavoisier,  Berthollet, 


* Ann.  of  Philos,  xvi.  273. 

t On  this  subject,  which  belongs  more  to  physics  than  chemistry,  see  the  able  outline 
in  Turner’s  Elements , p.  109. 

t For  figures  and  description  of  magnetic  electrical  apparatus,  see  Amer.  Jour. 
xxxiii-  p.  213,  and  xxxiv  p.  368. 


Oxides— Acids — Salts. 


103 


Morveau,  and  Fourcroy.t  Such  names  as  had  been  already  given  gee,  i. 
to  the  known  elementary  substances,  and  the  more  familiar  com- 
pounds were  retained.  To  the  newly  discovered  elements,  names 
were  given  expressive  of  some  striking  property.  To  the  beautiful 
element,  to  which  the  property  of  imparting  acidity  was  believed  ex-  Pfri^Pks 
clusively  to  belong,  the  name  oxygen  was  given,  from  the  Greek  menclature. 
o%tig  acid,  and  yeweiv  to  generate  : to  inflammable  air,  which,  with 
oxygen  composes  water,  the  name  hydrogen  was  given,  from  tiding 
water,  and  ysvvsiv.  New  elementary  substances  have  since  been 
named  on  the  same  principle,  as  the  green  gas  chlorine  from  xhwgog 
green  ; iodine  from  its  violet  colour,  ’I wdr/g  violet,  &c. 

322.  The  act  of  combining  with  oxygen  was  called  oxidation,  and  Oxidation, 
bodies  which  had  united  with  it  were  said  to  be  oxidized.  Com- 
pounds, of  which  oxygen  forms  a part,  were  called  acids  or  oxides , Acids^and 
according  as  they  do  or  do  not  possess  acidity.  An  oxide  of  copper  0X1  es‘ 

or  iron  signified  a combination  of  those  metals  with  oxygen,  which 
had  no  acid  properties.  The  termination  ide  was  also  applied  to  simi- 
lar combinations  of  chlorine,  iodine,  &c.,  thus  we  have  chlorides , 
iodides , fyc. 

323.  The  combinations  of  the  simple  non-metallic  substances,  ei-  xjrets. 
ther  with  one  another,  with  a metal,  or  with  a metallic  oxide,  were 
denoted  by  the  termination  uret.  Thus  sulphuret  and  carburet  of 

iron,  signify  compounds  of  sulphur  and  carbon  with  iron.  The  dif-  Oxides  how 
ferent  oxides  or  sulphurets  of  the  same  substance  were  distinguished  dis.t1"*, 
from  one  another  by  some  epithet,  which  was  commonly  derived 
from  the  colour  of  the  compound,  as  black  and  red  oxides  of  iron, 
black  and  red  sulphurets  of  mercury.  Though  this  practice  is  still  con- 
tinued occasionally,  it  is  now  more  customary  to  distinguish  degrees 
of  oxidation  by  the  use  of  derivatives  from  the  Greek  or  Latin. 

Thus  the  protoxide  of  a metal  denotes  the  compound  containing  the 
minimum  of  oxygen,  or  the  first  oxide  which  the  metal  is  known  to 
form,  £moxide  the  second,  ter  or  Zrifoxide  the  third  ; and  when  per- 
oxide is  employed,  it  denotes  the  highest  degree  of  oxidation.  The  Sesquiox- 
Latin  word  sesqui,  one  and  a half,  is  used  as  an  affix  to  an  oxide,  ides- 
the  oxygen  in  which  is  to  that  in  the  first  oxide  as  1£  to  1,  or  as  3 to 
2.  The  sulphurets,  carburets,  &c.,  of  the  same  substance  are  desig- 
nated in  a similar  way. 

324.  The  name  of  an  acid  was  derived  from  the  substance  acidi-  Acids, 
fied  by  the  oxygen,  to  which  was  added  the  termination  in  ic.  Thus 
sulphuric  and  carbonic  acids,  signify  acid  compounds  of  sulphur  and 
carbon  with  oxygen.  If  sulphur  or  any  other  body  should  form  two 
acids,  that  which  contains  the  least  quantity  of  oxygen  is  made  to 
terminate  in  ous , as  sulphurous  acid. 

325.  Compounds  consisting  of  acids  in  combination  with  metallic  Salts- 
oxides,  or  any  alkaline  bases,  were  termed  salts , the  names  of  which 
were  so  contrived  as  to  indicate  the  substances  contained  in  them. 

If  the  acidified  substance  contained  a maximum  of  oxygen,  the  name 
of  the  salt  terminated  in  ate  ; if  a minimum,  the  termination  in  ite 
was  employed.  Thus  the  sulphate,  phosphate,  and  arseniate  of  po~ 
tassa,  are  salts  of  sulphuric,  phosphoric,  and  arsenic  acids  ; while 


* For  interesting  biographies  of  these  eminent  men,  see  Thomson’s  History  of 
Chemistry , yoI.  ii. 


104 


Nomenclature. 


Chap,  ii.  the  terms  sulphite,  phosphite,  and  arsenite  of  potassa,  denote  combi- 
nations of  that  alkali  with  the  sulphurous,  phosphorous,  and  arseni- 
ous  acids. 

326.  After  the  discovery  of  the  laws  of  chemical  combination,  the 
Neutral,  nomenclature  was  much  improved.  What  were  before  called  neutral 
salts , from  the  acid  and  alkali  being  in  such  proportions  as  to  neu- 
Super-salts.tralize  each  other,  swjoer-salts  from  the  prevalence  of  acid,  and  sub- 
salts  from  the  excess  of  alkali,  were  named  from  their  atomic  consti- 
Atomic  tution.  If  the  salt  is  a compound  of  one  proportion  of  the  acid  and 
tkmmclVca  oener>c  nama  of  the  salt  is  employed  without  any 

ted.  other  addition  ; but  if  two  or  more  proportions  of  the  acid  are 
attached  to  one  of  the  base,  or  two  or  more  of  the  base  to  one  of 
the  acid,  a numeral  is  prefixed  so  as  to  indicate  its  composition. 
The  two  salts  of  sulphuric  acid  and  potassa  are  called  sulphate 
and  ^'sulphate ; the  first  containing  an  equivalent  of  the  acid 
and  the  alkali,  and  the  second  salt,  two  of  the  former  to  one 
of  the  latter.  The  three  salts  of  oxalic  acid  and  potassa  are 
termed  the  oxalate,  fo'noxalate,  and  ^wadroxalate  of  potassa  ; because 
one  equivalent  of  the  alkali  is  united  with  one  equivalent  of  acid 
in  the  first,  with  two  in  the  second,  and  with  four  in  the  third  salt.* 
More  ex-  327.  The  views  of  chemists  in  regard  tq  acids,  alkalies,  and  salts, 
▼lews  of  have  been  much  extended.  Several  of  the  metals  form  acids  with 
suits,  &c.  oxygen,  and  others  alkalies.  The  acids  and  alkalies  give  rise  to 
compounds  more  complex  than  themselves,  containing  at  least  three 
elements,  and  these  are  known  by  the  name  of  salts  ; most  of  them 
unite  in  definite  proportions  with  certain  substances,  and,  with  other 
salts,  forming  double  salts . Chemists  are  now  inclined  to  consider  as 
acids  all  compounds  which  unite  with  potassa  or  ammonia,  and  give 
rise  to  bodies  similar  in  constitution  and  general  character  to  the  salts 
which  the  sulphuric  or  some  admitted  acid  forms  with  those  alkalies. 
Alkalies.  328.  The  characters  of  alkalies  are  exhibited  most  perfectly  in 
potassa  and  soda;  they  are  causticity,  a peculiar  pungent  taste,  alka- 
line reaction  with  test  paper,  and  power  of  neutralizing  acids,  and 
especially  of  forming  with  them  neutral  saline  compounds.  Such 
Salifiable  are  ca^e^  olkaline  or  salifiable  bases , which  unite  definitely  with  ad- 
bases.  mitted  acids,  and  form  compounds  analogous  in  constitution  to  the 
salts  from  admitted  alkalies  and  acids. 

Salts  are  329.  The  salts  are  now  viewed  as  compounds  of  oxidized  bodies, 
compounds  b0th  ^e  acid  an(J  base  containing  oxygen.  Ammonia,  though  not 
bodies. 1ZCd  an  oxide,  has  all  the  characters  of  an  alkali,  and  its  compounds  with 
acids  are  admitted  as  salts. 

Orders.  330.  Salts  have  been  divided  by  Turner  into  four  orders,  viz.  1.  oxy - 
salts  ; 2.  hydro-salts  ; 3.  sulphur-salts  ; and  4.  haloid-salts.  In  the 
first,  the  acid  or  base  is  an  oxidized  body,  in  the  second  it  contains 
hydrogen,  in  the  third  the  electro-positive  or  negative  ingredient  is 
a sulphuret,  and  in  the  fourth  it  is  haloidal. 

The  nomenclature  of  the  hydro  salts  is  framed  on  the  same  princi- 


, * As  the  numerals  which  denote  the  equivalents  of  the  acid  in  a super  salt  are  de- 

ni«thod°,n  ' rived  from  the  Latin,  it  has  been  proposed  by  Thomson  to  employ  the  Greek  numerals 
dis , tris , tctrakis . to  signify  the  equivalents  of  alkali  in  a subsalt.  Turner  has  extended 
this  by  distinguishing  two  or  more  equivalents  of  the  negatively  electrical  element  by 
Latin  numerals,  and  the  positive  element  by  Greek  numerals.  Thus  a bichloride  de- 
notes a compound  which  contains  two  equivalents  of  the  negative  element  chlorine ; 
and  dichloride  indicates  one  equivalent  of  chlorine  with  two  of  some  positive  body. 


Salts — Gas. 


105 


pies  as  those  applied  to  salts  which  contain  oxygen.  No  general  Sect,  i. 
principle  of  nomenclature  has  yet  been  agreed  upon  with  respect  to 
the  third  and  fourth  order.  Berzelius  has  extended  to  them  the 
same  nomenclature  which  he  employs  for  the  oxy-salts. 

331.  The  haloid- salts  of  Berzelius  (from  &lg  Sea-salt,  and  sldog 
form)  are  those  which,  in  constitution,  are  analogous  to  sea-salt.  saJt“ 
They  are,  for  the  most  part,  bi-elementary,  consisting  of  a metal,  and 

of  chlorine,  iodine,  bromine,  fluorine  and  the  radicals  of  the  hydr- 
acids.^  The  haloid-salts  are  analogous  to  oxides  and  sulphurets.t 

332.  In  the  compounds  of  metallic  sulphurets  (double  sulphurets) 

Berzelius  has  found  an  exact  analogy  with  the  salts,  and  called  them 
sulphur-salts.  The  union  of  simple  sulphurets  forms  a sulphur-sa\t  Sulphur 
analogous  in  constitution  to  acids  and  alkaline  bases,  and  which,  like 
them,  are  capable  of  assuming  opposite  electric  energies  in  relation  us> 

to  each  other.  Electro-positive  sulphurets  are  termed  sulphur ■* 
bases,  and  are  usually  the  protosulphurets  of  electro-positive  me- 
tals, corresponding  to  the  alkaline  bases  of  those  metals.  Electro- 
negative sulphurets,  sulphur  acids , are  the  sulphurets  of  electro- 
negative metals,  and  are  proportional  in  composition  to  the  acids 
which  the  same  metals  form  with  oxygen.  Hence  if  the  sulphur 
of  a sulphur-salt  were  replaced  by  an  equivalent  of  oxygen,  an 
oxy-salt  would  result. 

333.  Most  salts  a re  solid  at  common  temperatures  and  susceptible  characters 
of  crystallization  ; they  vary  in  colour.  The  soluble  salts  are  more  of  salts, 
or  less  sapid,  the  insoluble  are  insipid ; few  of  them  possess  odour. 

They  differ  in  their  affinity  for  water  (page  5),  and  in  solubility. 

Some  dissolve  in  less  than  their  weight  of  water  ; others  require  se- 
veral hundred  times  their  weight ; others  are  quite  insoluble  ; this 
difference  depends  on  their  affinity  for  water,  and  on  their  cohesion ; 
their  solubility  being  in  direct  ratio  with  the  first,  and  in  inverse  ratio 
with  the  second. 

334.  The  relative  degrees  of  affinity  of  salts  for  water  may  be  Affinity  of 
estimated  by  dissolving,  equal  quantities  of  salts  in  equal  quantities  sal*s  for 
of  water,  and  heating  the  solution.  That  salt  which  has  the  great- ^i-mined" 
est  affinity  for  the  menstruum  will  retain  it  with  most  force,  and  will, 
therefore,  require  the  highest  temperature  for  boiling.! 

335.  The  term  gas  is  applied  to  those  elastic  fluids,  except  the  at- Gas,  what, 
mosphere,  which  retain  their  aeriform  state  at  common  temperatures, 

and  which  cannot  be  made  to  change  their  form  unless  by  much 
greater  pressure  than  they  are  naturally  exposed  to.  They  differ 
from  vapours  in  the  relative  forces  with  which  they  resist  condensation. 


*The  metallic  chlorides,  iodides,  bromides,  and  fluorides,  the  cyanurets,  sulphocy- 
anurets,  and  ferrocyanurets,  are  included  by  Berzelius  among  the  haloid  salts.  (Ann. 
de  Chim . et  de  Phys.  xxxii.  60.) 

t On  this  subject  consult  Turner’s  Elements , 404.  The  haloid  salts  of  Berzelius  are 
the  haloid  acids  and  bases  of  Turner,  and  the  double  haloid  salts  of  the  former  are 
the  haloid  salts  of  the  latter  chemist. 
t Gay  Lussac,  An.  de  Chim.  lxxxii. 

14 


V 


106 


Apparatus  and  Manipulation. 


-Chap.  II. 


Apparatus. 


Gas  bottles. 


Apparatus 
for  gases, 
requiring 
red  heat. 


Coating  of  ?c*- 

■•1*. 


Section  II.  Apparatus  and  Manipulation. 

336.  For  performing  experiments  on  gases,  several  articles  of  apparatus  are  ne- 
cessary, consisting  partly  of  vessels  fitied  for  containing  the  materials  that  afford 
them,  and  partly  of  vessels  adapted  to  the  reception  of  gases,  and  for  submitting 
them  to  experiment. 

For  procuring  such  gases  as  are  producible  without  a very  strong  heat,  glass 
vessels,  furnished  with  ground  stoppers  and  bent  tubes  are  sufficient  Of  these, 
several  will  be  required  of  different  sizes  and  shapes.  A Florence  flask,  with  a 


Fig.  85.  Fig.  86.  Fig.  87. 


cork  perforated  by  a bent  glass  tube,  or  even  a tin  pipe,  will  serve,  for  obtaining 
some  of  the  gases.  Those  gases  that  require  for  their  liberation  a red  heat,  may 
be  procured  by  exposing  to  heat  the  substances  capable  of  affording  them,  in 
coated  earthen  retorts  or  tubes,"  or  in  a gun  barrel,  the  touch-hole  of  which  has 
been  accurately  closed  by  an  iron  pin.  To  the  mouth  of  the  barrel  must  be  af- 
fixed a tube  bent  so  as  to  convey  the  gas  where  it  may  be  requisite. + 

A very  convenient  apparatus  for  obtaining  such  gases  as  cannot  be  disengaged 
without  a red  heat,  consists  of  a cast-iron  retort  (Fig  89).  This  may  have  a 
jointed  metallic  conducting  tube  fitted  to  it  by  grinding  (Fig.  90).  It  is  repre- 
sented as  placed,  when  in  actual  use,  within  the  bars  of  a common  fire-grate,  13. 
(Fig.  102.)  The  wrought  iron  bottles  in  which  quicksilver  is  imported,  form  conve- 
nient retorts  for  this  purpose,  a gun  barrel  being  screwed  into  the  neck  of  the  bottle. 
When  these  are  used  (as  for  obtaining  oxygen  gas),  the  fuel  should  be  charcoal ; 
they  are  liable  to  melt  if  anthracite  coal  is  used. 


♦When  a coating  must  sustain  a very  high  temperature,  it  should  be  made  of  the 
best  Stourbridge  clay,  made  into  a paste,  beaten  uutil  perfectly  elastic  and  uniform. 
A portion  should  be  flattened  out  into  a cake  of  the  required  thickness  and  size  adapt- 
ed to  the  vessel.  If  the  vessel  he  a retort  or  flask,  it  should  be  placed  in  the  middle 
of  the  cake,  and  the  edge  of  the  latter  be  raised  on  all  sides,  and  gradually  moulded 
and  applied  to  the  glass  ; if  it  be  a tube,  it  should  be  laid  upon  one  edge  of  the  plate, 
and  then  applied  by  slowly  rolling  the  tube  forward.  In  all  cases  the  surface  to  be 
coated  should  be  rubbed  over  with  a piece  of  the  lute  dipped  in  water,  for  the  purpose 
of  moistening,  and  leaving  a little  of  the  earth  upon  it;  and  if  any  part  of  the  surface 
becomes  dry  before  the  lute  is  applied,  it  should  be  remoistened.  The  lute  should  be 
pressed  and  rubbed  down  upon  tne  glass,  successively,  from  the  part  where  the  contact 
was  first  made  to  the  edges,  until  all  air  bubbles  are  excluded,  and  an  intimate  adhe- 
sion effected.  Care  must  be  taken  to  exclude  all  air  from  between  the  glass  and  lute, 
and  the  edges  should  he  moistened,  made  thin,  and  joined  with  great  care.  The  ge- 
neral thickness  may  be  from  one  fourth  to  one  third  of  an  inch.  The  vessels  are  af- 
terwards to  be  placed  in  a warm  situation  over  the  sand  bath,  or  in  the  sun’s  rays: 
they  should  dry  slowly  and  regularly.  To  prevent  cracking,  horse  dung,  chopped  hay, 
horse  hair,  and  tow  cut  short  may  be  incorporated  with  the  lute.  The  addition  of 
sand,  renders  the  lute  more  fusible,  and  is  not  applicable  when  very  high  temperatures 
are  to  be  sustained.  In  such  cases  fragments  ef  broken  glass  pots,  or  of  broken  cruci- 
bles, may  be  used,  being  first  well  pulverized  ; but  crucibles,  soiled  by  flux  or  other 
impurities  must  not  be  so  employed.  For  various  kinds  of  lutes  and  cements,  and  di- 
rections for  their  application,  &c.,  see  Faraday’s  Chem.  Manip.  p.  467. 

t Great  convenience  often  arises  from  prolonging  the  tube  by  means  of  flexible 
tubes  or  hoses  5 and  any  num- 
ber of  them  may  be  cohnect- 
ed  by  the  attached  screw’s 
Fig.  95. 


Gasometers. 


107 


For  receiving  the  gases,  glass  jars  of  various'sizes  are  required,  some  of  which  Apparatu* 
should  be  furnished  with  necks*  at  the  top,  fitted  with  ground  stoppers,  or  to  for  receir- 
which  a circular  plate  of  brass  is  well  ground.  (Fig.  91  and  92.)  inS  gase*. 


Fig.  91.  Fig.  92. 


Others  should  be  provided  with  brass  caps  and  screws  for  the 
reception  of  air  cocks.  (Fig.  9'd.)  Of  these  air  cocks  several  will 
be  necessary,  and  to  some  of  them  bladders,  (Fig.  94,  a,)*  or  elas- 
tic bottles,  should  be  firmly  tied  for  the  purpose  of  transferring 


Fig.  93. 


Fig  94. 


* A bladder  may  be  made  to  continue  tight  for  a considerable  period  by  pouring  a 
little  oil  into  it  at  first,  and  allowing  it  to  become  saturated.  Bladders  are  not  per- 
fectly tight  to  gases,  and  are  less  so  when  dry  than  when  moist ; consequently  gases 
shou'd  not  be  retained  long  in  them,  and  never  longer  than  is  absolutely  necessary. 
Hydrogen  gas  passes  more  rapidly  through  them  than  any  other  gas. 

Gas  bags  are  made  of  oiled  silk,  or  of  two  layers  of  woven  material,  haying  between 
them  a thick  layer  of  caoutchouc.  Those  made  of  oiled  silk  are  seldom  tight,  and  ra- 
pidly increase  in  porosity.  F. 


108 


Chap.  II. 


Pneumatic 

trough. 


Graduated 

tubes. 


Gasometer. 


Transfer- 
ring of 
gases. 


•Apparatus  and  Manipulation. 

a few  gallons  of  water.  This  is  best  made  of  copper,  (Fig.  96,  6,)  if  of 
siderable  size;  or  if  small,  of  tin,  japanned  or  painted;  //,  ezhibi 


con- 
ezhibits  a 


Fig.  96. 


Fig-  97. 


section  of  this  apparatus,  which  has  been  termed  the  pneumato-cbemical  trough, 
or  pneumatic  cistern.  Its  size»may  vary  with  that  of  the  jars  employed  ; and, 
about  one  or  two  inches  from  the  top,  it  should  have  a shelf  on  which 
the  jars  may  be  placed  when  filled  with  air,  without  the  risk  of  being  over- 
set. In  this  shell*  should  be  a few  small  holes,  to  which  inverted  funnels  may 
be  soldered.  Fig.  97  represents  a very  convenient  Fig.  98. 

form  of'  this  apparatus.  A glass  tube,  Fig.  98,  about  l t t t 1 ( t 

IS  inches  long  and  three  fourths  of  an  inch  in  diam-  1 ' 1 - 1 1111  1 J 

eter,  closed  at  one  end,  and  di\  ided  into  cubic  inches  and  tenths  of  inches  will  be 


5 p1 

small  measure,  containing  about  two  cubic  inches,  and  similarly  Fig 
graduated.  Glass  tubes  about  five  inches  long,  and  half  an  inch 
wide,  divided  decimally,  are  also  necessary.  Besides  these,  the  experi- 
mentalist should  be  furnished  with  air  funnels,  (Fig.  99).  for  tram  ’ 
ring  gases  from  wide  to  narrow  vessels. 

337.  An  apparatus  almost  indispensable  in  experiments  on  this  class  of  bodies, 
is  a Gasometf.r,  which  enables  the  chemist  to  collect  and  to  preserve  large 
quantities  of  gas,  with  the  aid  of  only  a few  pounds  of  water.  In  the  form  of 
this  apparatus  there  is  considerable  variety  ; its  general  construction  and  use  is 


inch  n 
peri- 

isfer-  f \ 


as  follows.  It  consists  of  an  outer  fixed  vessel  d,  (Fig.  100), 
and  an  inner  movable  one  c,  both  of  copper  or  japanned 
iron.  The  latter  slides  easily  up  and  down  within  the  other, 
and  is  suspended  by  cords  passing  over  pullics,  to  which  are 
attached  the  counterpoises  e e.  To  avoid  the  incumbrance 
of  a great  weight  of  water,  the  outer  vessel  d is  made  double, 
or  is  composed  of  two  cylinders,  the  inner  one  of  which  is 
closed  at  the  top  and  at  the  bottom.  The  space  of  only 
about  half  an  inch  is  left  between  the  two  cylinders,  as 
shown  by  the  dotted  lines.  In  this  space  the  vessel  c may 
move  freely  up  and  down.  The  interval  is  filled  with  wa- 
ter ns  high  as  the  top  of  the  inner  cylinder.  The  cup,  or 
rim,  at  the  top  of  the  outer  vessel,  is  to  prevent  the  water 
from  overflowing,  wdien  the  vessel  c is  forcibly  pressed 


Fig.  100. 


\4 

'gj- 1 

l| 

to  be  collected.  The  gas  enters  from  the  vessel  in  which  it  is  produced,  by  the 
communicating  pipe  &,  and  passes  along  the  perpendicular  pipe,  marked  by  dot- 
ted lines  in  the  centre,  into  the  cavity  of  the  vessel  c,  which  continues  rising  till 
it  is  full. 

338.  To  transfer  the  gas  or  to  apply  it  to  any  purpose,  the  cock  b is  to  be  shut, 
and  an  empty  bladder,  or  bottle  of  elastic  gum,  furnished  with  a stop-cock,  to  be 
screwed  on,  a.  When  the  vessel  c is  pressed  down  with  the  hand,  the  gas 
passes  down  the  central  pipe,  which  it  had  before  ascended,  and  its  escape  at  b 
being  prevented,  it  finds  its  w'av  up  a pipe  which  is  fixed  to  the  outer  surface  of 
the  vessel,  and  which  is  terminated  by  the  cock  a.  By  means  of  an  ivory 
mouth-piece  screwed  upon  this  cock,  the  gas,  included  in  the  instrument, 
may  be  respired  ; the  nostrils  being  closed  by  the  fingers.  When  it  is  re- 
quired to  transfer  the  gas  into  glass  jars  standing  inverted  in  water,  a crook- 


Gas-holders , 


109 


ed  tube  may  be  employed,  one  end  of  which  is  screwed  upon  the  cock  b ; while 
the  other  aperture  is  brought  under  the  inverted  funnel,  fixed  into  the  shelf  of 
the  pneumatic  trough. 

339.  When  large  quantities  of  gas  are  required,  (as  at  a public  lecture),  the 
gas-holder  (Fig.  101)  will  be  found  extremely  useful.  It  is  made  pig.  ioj. 
of  copper  or  tinned  iron-plate,  japanned  botli  within  and  with- 
out. Two  short  pipes,  a and  c,  terminated  by  cocks,  proceed 
from  its  sides,  and  another,  ft,  passes  through  the  middle  of  the 
top  or  cover,  to  which  it  is  soldered,  and  reaches  within  half  an 
inch  of  the  bottom.  It  will  be  found  convenient  also  to  have  an 
air  cock  with  a very  wide  bore,  fixed  to  the  funnel  at  b.  When 
gas  is  to  be  transferred  into  this  vessel  from  the  gasometer,  the 
vessel  is  first  completely  filled  with  water  through  the  funnel, 
the  cock  a being  left  open  and  c shut.  By  means  of  a horizon- 
tal pipe,  the  aperture  a is  connected  with  a of  the  gasometer. 

The  cock  b being  shut,  a and  c are  open,  and  the  vessel  c of  the 
gasometer  (Fig.  100),  gently  pressed  downwards  with  the  hand. 

The  gas  then  descends  from  the  gasometer  till  the  air-holder  is 
full,  which  may  be  known  by  the  water  ceasing  to  escape  through  the  cock 
All  the  cocks  are  then  to  be  shut,  Fi  1Q2 

and  the  Vessels  disunited.  To  ap- 
ply this  gas  to  any  purpose,  an 
empty  bladder  may  be  screwed  on 
a ; and  water  being  poured  through 
the  funnel  b , a corresponding  quan- 
tity of  gas  is  forced  into  the  blad- 
der. By  lengthening  the  pipe  6, 
the  pressure  of  a column  of  water 
may  be  added  : and  the  gas,  being 
forced  through  a with  considerable 
velocity,  may  be  applied  to  the 
purposes  of  a blow-pipe,  &c.  &c. 

The  apparatus  admits  of  a variety 
of  modifications.  The  most  useful 
one  appears  to  be  that  contrived  by 
Pepys,  consisting  chiefly  in  the  ad- 
dition of  a shallow  cistern  (Fig. 

102,  c)  to  the  top  of  the  air-holder, 
and  of  a glass  register  tube  /,  which 
shows  the  height  of  the  water,  and( 
consequently  the  quantity  of  gas, 

in  the  vessel.  When  a jar  is  intended  to  be  filled  with  gas  from  the  reservoir, 
it  is  placed,  filled  with  water,  and  inverted  in  the  cistern  c.  The  cocks  1 and  2 
being  opened,  the  water  descends  through  the  pipe  attached  to  the  latter,  and 
the  gas  rises  through  the  pipe  e.  By  raising  the  cistern  a to  a greater  elevation, 
any  degree  of  pressure  may  be  obtained ; and  a blow-pipe  may  be  screwed  on 
the  cock  at  the  left  side  of  the  vessel.* 

340.  A very  convenient  apparatus  was  contrived  by  Hope,  for  receiving  and 
storing  large  quantities  of  gases  most  in  use,  from  which  a supply  may  be  easily 
procured  as  wanted.  It  consists  of  a large  oil  of  vitriol  bottle  a,  or  carboy, 
(Fig  103. ) in  which  two  tubes  with  stop-cocks  are  fitted,  water  being  introduced 
and  forced  out  again  when  necessary  by  one,  and  gas  by  the  other.  In  the  figure  i 


* It  is  necessary  to  be  aware  of  the  possible  entrance  of  common  air  with  the  water, 
even  when  there  is  considerable  depth  in  the  cistern.  When  the  gas  is  passing  ra- 
pidlyr  out  at  the  lateral  stop-cock,  and  consequently  the  water  rapidly  descending 
through  the  tube,  it  will,  if  unattended  to,  frequently  acquire  a rotary  motion,  which, 
from  mechanical  causes  easily  explained,  will  at  last  produce  an  aperture  commencing 
at  the  surface  of  the  water  and  descending  to  the  very  bottom  of  the  tube.  Down  this, 
air  is  rapidly  carried  by  the  descending  water,  which,  mixing  with  the  gas  in  the  in- 
strument, deteriorates  it,  and  with  inflammable  gases  may  lead  to  dangerous  results. 
Hence  this  rotary  motion  when  observed,  should  be  disturbed.  The  formation  of  the 
central  channel  for  air  may  easily  be  prevented  by  allowing  a large  bung  or  piece  of 
light  wood  to  swim  on  the  surface  of  the  water.  If  rotation  does  take  place,  it  will 
draw  the  floating  mass  to  the  centre,  and  prevent  the  air  from  passirg  down  by  hin- 
dering the  formation  of  a channel,  if  water  be  plentifully  supplied.  F.  362. 


Sect.  II. 


Gas-holder. 


Hope’s 
gas-hold  er. 


Precaution*. 


110 


Chap.  II.  t 


Transfer- 
ring from. 


Mercurial 

gasome- 

ters. 


Nermann’* 

mercurial 

trough. 


Apparatus  and  Manipulation. 


may  be  supposed  in  connexion  with  the  extremity  of  a bent 
gun  barrel  fixed  in  an  iron  retort,  from  which  oxygen  is 
passing  To  prevent  accident  and  render  it  more  easily 
movable  when  full  of  water,  it  should  be  placed  in  a 
tub,  the  space  between  the  bottle  and  sides  as  well  as 
the  bottom  are  packed  with  saw  dust.  After  filling  it 
with  water,  a bent  tube  is  connected  with  the  gun  barrel 
by  a flexible  lead  or  tin  pipe  two  or  three  feet  in  length. 

No  gas  is  allowed  to  pass  in  unless  pure,  the  stop-cock  at 
the  extremity  of  the  gun  barrel,  //,  being  kept  shut,  while 
the  other  one  c,  is  open.  The  gas  first  passing  over  can  be  collected  by  means 
of  a bent  tube  d fitted  to  it,  in  a small  jar  over  water,  so  that  its  purity  can  be 
tested.  When  it  is  thought  proper  to  commence  collecting  it,  the  stop-cock  c is 
to  be  shut  and  the  other  b opened.  As  the  gas  enters,  the  water  will  be  forced 
up  the  tube  seen  in  the  interior  of  the  bottle  continuous  with  the  stop-cock  e at- 
tached to  the  cap  of  the  carboy ; and  another  bent  tube  being  placed  over  it  a 
syphon  will  bo  formed,  through  which  the  water  will  continue  to  flow  as  the 
gas  enters.  By  using  a large  quantity  of  materials  at  a time,  several  bottles  may 
be  filled  successively  without  undoing  any  part  of  the  apparatus,  except  the 
leaden  pipe  that  connects  them  directly  with  the  gun  barrel ; one  bottle  may  be 
detached  and  another  attached  in  a few  seconds.  If  wanted,  jars  of  gas  may  be 
collected  from  the  tube  d in  the  pneumatic  trough. 

To  transfer  a gas  from  this  apparatus,  detach  the  syphon,  place  a 
tin  funnel  z,  (Fig.  10-1,)  above  the  stop-cock  e,  pour  in  water  and 
open  the  stop-cocks;  it  will  descend  and  force  the  gas  out  at  the  stop- 
cock g,  to  which  a flexible  pipe  may  be  attached.  In  the  same 
manner  the  air  is  expelled  and  the  carboy  filled  with  wrater  before 
connecting  it  with  the  retort  furnishing  the  gas. 

341.  The  gasometers  already  described,  are  fitted  only  for  the 
reception  of  gases  that  are  confinable  by  water ; because  quick- 
silver would  act  on  tho  tinning  and  solder  of  the  vessels  ; and 
would  not  only  be  spoiled  itself,  but  would  destroy  the  apparatus.  Yet  an  in- 
strument of  this  kind,  in  which  mercury  can  be  employed,  is  peculiarly  desira- 
ble, on  account  of  the  great  weight  of  that  fluid  ; and  two  varieties  of  the  mer- 
curial gasometer  have  therefore  been  invented.  In  that  invented  by  Pepys,  the 
cistern  for  the  mercury  is  of  cast  iron.  Newmann  has  joined  a gasometer  of  this 
kind  to  an  improved  mercurial  trough,  by  means  of  which  the  advantage  of  both 
are  obtained  with  only  CO  or  70  pounds  of  quicksilver.*  Fig.  105. 


Fig.  104. 


Fig.  103. 


* It  is  not  more  than  18  inches  in  length  and  height;  and  it  is  placed  in  a large  jap- 
panned  tray  to  collect  scattered  mercury. 

When  gas  is  to  be  collected  in  the  Fig.  105. 

gasometer,  the  beak  of  the  retort  is 
placed  below  the  surface  of  the  mercu- 
ry, in  the  cup  at  the  bottom  of  the  ap- 
paratus, and  bavin"  a bell  shaped  ves- 
sel immersed  in  the  mercury  imme- 
diately over  it.  The  trough  has  a 
cavity  in  the  middle,  large  enough  to 
fill  a jar  10  inches  long,  and  24  wide  ; 
and  there  is  a shelf  on  each  side,  three 
inches  in  width,  to  support  vessels  con- 
taining gas.  Opposite  to  three  inden- 
tations op  the  edge  of  the  trough,  are 
three  holes  in  one  of  the  shelves,  into 
which  the  beaks  of  retorts  libera- 
ting gas  are  to  be  introduced;  or  a sli- 
ding shelf  with  apertures  may  be  fit- 
ted across  the  cavity  for  the  same  pur- 
pose. The  gasometer  is  at  one  end, 
a,  and  sunk  below  the  level  of  the 
trough.  It  is  capable  of  containing  50 
cubic  inches.  A tube,  connected  with 
the  gasometer  at  the  lower  part  is  r- 

made  to  ascend,  and  passing  up  \. 

through  the  mercury  in  a corner  of  the  trough,  at  about  an  inch  above  it  bends  down 
again  and  termiuates  beneath  its  surface.  If  the  gas  is  contained  in  the  gasometer,  it 


Furnaces. 


Ill 


For  the  mere  exhibition  of  a few  experiments,  a small  trough,  eleven  inches  Sect.  II. 
long,  two  wide,  and  two  deep,  cut  out  of  a solid  block  of  mahogany,  (or  soap- 
stone) is  sufficient. 

342.  The'materials  from  which  some  gases  are  to  be  obtained,  require  the  aid 
of  a high  temperature  and  a suitable  furnace.  Various  kinds  of  furnaces  are 
required  by  the  chemist,  of  which  figures  and  descriptions  will  be  seen  in  Fara- 
day’s Chemical  Manipulation* * 

For  many  processes  a very  convenient  furnace  may  be  formed  out  of  the  large  Furnaces, 
crucibles  known  as  blue  pots , and  may  be  had  of  almost  every  size  less  than  the 
height  of  22  inches,  and  of  12  to  14  inches  diameter  at  the  top.  One  of  these 
vessels,  of  the  height  of  12  inches,  and  7 inches  wide  at  the  top,  will  make  a 
very  useful  furnace  for  the  igniting  of  a small  crucible,  heating  a tube,  or  small 
retort.  Fig.  107.  A number  of  holes  are  pierced  in  it,  by  a gim-  Fig.  107. 
let  or  brad  awl,  and  enlarged  by  a round  rasp.  The  pot  is  now  bound 
round  with  iron  or  copper  wire,  to  strengthen  and  hold  it  together 
when  it  cracks,  an  effect  which  is  sure  to  take  place  after  it  has  been 
a few  times  heated.  This  wire  should  be  carried  round  in  three  differ- 
ent places,  and  secured  by  notches  made  in  the  pot  with  the  edge  of 
a rasp,  and  the  ends  should  then  be  twisted  together.  It  is  also  con- 
venient to  have  a handle  to  these  furnaces. 

A movable  grate  like  that  figured  in  the  wood  cut,  makes  this  furnace  com- 
plete for  many  operations.  Fig.  108.  If  it  be  required  to  heat  a crucible,  the 
grate  should  be  of  such  a size  as  to  drop  into  the  furnace,  and  rest  between  the 
bottom  and  the  second  row  of  holes.  The  part  below  then  forms  the  Fig.  108. 
ash-pit  to  be  supplied  with  air  by  the  four  holes;  and  the  part  above 
forms  the  body  of  the  furnace  to  receive  the  fire  and  the  crucible.  If 
a shallow  fire  only  is  wanted,  as  in  the  process  of  distillation  or  the 
heating  of  tubes,  the  grate  should  be  of  such  size  as,  when  dropped 


may  be  transferred  to  air-jars  in  the  trough,  by  filling  them  with  mercury,  Fig.106. 
placing  them  over  the  end  of  the  bent  tube,  and  giving  pressure  to  the  gasom- 
eter. The  air  will  pass  from  it  along  the  tube  into  the  jar.  By  the  bend  in 
the  tube,  the  mercury  is  prevented  from  passing  into  the  lower  part  of  the 
gasometer,  while  at  the  same  time  the  gas  is  allowed  a free  passage.  All 
inconvenience  is  prevented  by  means  of  a stop-cock,  which  shuts  off  the 
communication  between  the  receiver  and  the  trough,  preventing  at  the  same 
time  the  escape  of  air  from  the  gasometer,  and  of  mercury  into  it.  A sliding 
shelf  is  fixed  beneath  the  trough  to  support  a spirit-lamp  under  a retort,  or 
for  other  purposes.  A detonating  tube  b,  (Fig  106)  and  spring  are  also  at- 
tached to  the  apparatus  by  a clamp  and  screws,  and  may  be  fixed  on  any  side  of 
the  trough.  The  whole  apparatus  is  of  iron,  excepting  sometimes  the  pillars 
which  support  it,  and  which  maybe  of  brass.  See  another  form  Fig.  no. 


* A work  which  should  be  in  the  possession  of  every  chemical  student.  A furnace 
for  general  laboratory  use  which  has  been  found  powerful  and  convenient,  was  orig- 
inally constructed  for  the  Royal  Institution*  of  the  form  and  section  represented  in  the 
annexed  figures.  It  warms  and  airs  the  laboratory,  heats  water,  tubes,  gas  bottles,  a 
sand  bath,  &c.  The  principal  part  is  of  brick  work,  the  top  plate  A B,  sand  bath,  plate 
under  the  same  and  front  may  be  of  iron  or  soap  stone.  The  flue  is  carried  horizontally 


under  the  sand  bath,  and  a warm  chamber  is  left  beneath,  which  is  closed  by  doors, 
in  which  crucibles  or  other  vessels  may  be  kept  warm,  ready  for  introduction  into  the 
furnace,  and  slow  evaporations  be  carried  on.  The  circular  opening  in  front,  over 
the  fire  chamber,  is  adapted  to  receive  various  vessels,  by  means  of  concentric  iron 
rings  of  various  diameters,  on  a cast  iron  pot. 


_ * Furnaces  of  this  kind  have  for  several  years  past,  been  in  use  in  the  laboratory  of  the  Univer- 
sity at  Cambridge,  and  in  that  of  the  Medidal  College  in  Boston,  and  proved  admirably  adapted 
for  all  purposes.  For  minute  description  see  Faraday,  p.  90. 


112 


* Apparatus  and  Manipulation. 


Chap.  II.  into  the  furnace,  to  descend  only  a little  below  the  first  tier  of  holes,  the  ash-pit 
having  two  tiers  of  holes  entering  it.  Half  a dozen  of  these  small  grates  will 
be  required  in  the  laboratory,  for  the  purpose  of  fitting  at  different  times  into 
different  parts  of  the  same  furnace,  and  also  for  use  in  different  sized  furnaces  of 
the  kind  now  described. 

When  we  wish  to  diminish  the  intensity  of  the  fire,  the  holes  or  a portion  of 
them  may  be  closed  with  soft  brick  or  clay  stoppers.  On  the  contrary, 
when  it  is  desirable  to  increase  the  temperature,  or  to  increase  the 
body  of  fuel,  additions  are  made  at  the  top  of  the  furnace.  A very 
useful  one  consists  of  the  upper  part  of  an  old  crucible  cut  off  so  as 
to  form  a ring,  (Fig.  109,)  which  should  be  bound  round  with  wire, 
as  was  directed  in  regard  to  the  furnace. 

A most  useful  accompaniment  to  these  small  portable  furnaces,  is 
a piece  of  straight  funnel  pipe,  about  two  feet  long,  four  inches  in 
width,  and  opening  out  below  until  it  is  about  eight  inches  in  diame- 
ter. Fig  110.  This  will  easily  rest  upon  any  furnace  not  more  than  c* 
eight  inches  nor  less  than  four  or  five  inches  wide  ; is  quickly  put 
on  or  otf;  stands  steadily  of  itself,  and  increases  the  draught  power- 
fully.  A wooden  handle  may  be  attached  to  it  for  convenience  ; or 
without  it,  the  tongs  will  serve  to  remove  it.  It  may  either  be  taken 
off’  when  the  fire  requires  to  be  made  up,  or  the  pieces  of  charcoal 
may  be  dropped  in  from  above.  There  is  no  difficulty  in  raising  a 
crucible  two  inches  and  a half  in  diameter  to  a white  heat,  by  a furnace  of  this 
kind,  and  that  in  any  situation  which  may  be  convenient,  upon  the  tables  or  the 
floor,  and  with  all  the  advantage  of  arrunirin<r  or  dismounting  the  apparatus  with 


Fig.  110. 


n 


Fig.  111. 


extreme  facility.* 

Annantus  A,  useful  apparatus,  for  submitting  gases  to 

for  submit-  action  of  electricity,  isahown  in  Fig.  Ill;  where 
ting  gases  a represents  the  knob  of  the  prime  conductor  of 
to  electri-  an  electrical  machine;  6,  a Leyden  jar,  the  ball  of 
city.  which  is  in  contact  with  it,  as  when  in  the  act  of 

charging;  and  c,  the  tube  standing  inverted  in 
mercury,  and  partly  filled  with  gas.  The  mercu- 
ry is  contained  in  a strong  wooden  box  <Z,  to  which 
is  screwed  the  upright  iron  pillar  e,  with  a sliding 
collar  for  securing  the  tube  c in  a perpendicular 
position.  When  the  jar  A,  is  charged  to  a certain 
intensity,  it  discharges  itself  between  the  knob  a 
and  the  small  ball  i,  which,  with  the  wire  con- 
nected with  it,  may  bo  occasionally  fitted  on  the  top  of  the  tube  c.  The  strength 
of  the  shocks  is  regulated  by  the  distance  between  a and  i. 

By  the  same  apparatus,  or  the  tube,  Fig.  106,  inflammable  mixtures  of  gase* 
may  be  exploded  by  electricity. 

Quantity  of  34-1.  The  proportion  of  gas  which  may  be  detonated  with  safety  in  a glass 
gas  to  be  tube,  depends  considerably  upon  the  explosive  power  of  the  (particular  mixture 
detonated,  under  examination,  and  also  upon  the  quantity  detonated  at  once.  A mixture  of 
oxygen  with  carbonic  oxide  expands,  when  inflamed,  with  much  less  force  than 
a mixture  of  oxygen  with  hydrogen  or  olefiant  gas  ; and  a large  quantity  will  of 
course  expand  with  more  force  than  a smaller.  But  besides  considering  the 
efficiency  of  the  tube  in  resisting  the  expansive  force,  occasioned  by  detonation, 
the  experimenter  has  also  so  to  proportion  the  quantity  of  gas,  that  whilst  ex- 
panding there  shall  be  abundant  space  in  the  tube  to  retain  the  products  under 
their  greatest  volume  and  agitation,  that  no  loss  may  occur.  No  more  gas  should 
be  introduced  into  a tube  for  detonation  than  will  occupy  a sixth  of  its  capacity 
at  common  temperatures,  and,  generally,  it  will  be  safer  and  advisable  to 
employ  much  less.  F.  433. 

Methods  of  345*  Previously  to  undertaking  experiments  on  the  gases,  it  may  be  well  for 
transferring  an  unpractised  experimentalist  to  accustom  himself  to  the  dexterous  manage- 
gases.  ment  of  gases,  by  transferring  common  air  from  one  vessel  to  another  of  differ- 
ent sizes. 

1.  When  a glass  jar,  closed  at  one  end,  is  filled  with  water,  and  held  with  its 


* Faraday  : who  remarks  that  all  the  ignitings  and  heatings  which  belong  to  the 
analysis  of  siliceous  and  other  minerals,  have  long  been  made  in  furnaces  of  this 
kind  at  the  Royal  Institution. 


Manipulation  with  Tubes.  113 

mouth  downwards,  in  however  small  a quantity  of  water,  the  fluid  is  retained  feect.  II.  - 
in  its  place  by  the  pressure  of  the  atmosphere  on  the  surface  of  the  exterior  “ n T - 
water.  Fill  in  this  manner,  and  invert,  on  the  shelf  of  the  pneumatic  trough, 
one  of  the  jars,  which  is  furnished  with  a stopper  (Fig.  91,)  The  water  will 
remain  in  the  jar  so  long  as  the  stopper  is  closed  ; but  immediately  on  removing 
it,  the  water  will  descend  to  the  same  level  within  as  without ; for  it  is  now 
pressed,  equally  upwards  and  downwards,  by  the  atmosphere,  and  falls  therefore 
in  consequence  of  its  own  gravity. 

2.  Place  the  jar,  filled  with  water  and  inverted,  over  one  of  the  funnels  of  jyrections 
the  sljelf  of  the  pneumatic  trough.  Then  take  another  jar,  filled  (as  it  will  be  ^ practice. 
of  course)  with  atmospherical  air.  Place  the  latter  with  its  mouth  on  the  sur-  ^ 

face  of  the  water;  and  on  pressing  it  in  the  same  position  below  the  surface,  the 
included  air  will  remain  in  its  situation.  Bring  the  mouth  of  the  jar  beneath  the 
funnel  in  the  shelf,  and  incline  it  gradually.  The  air  will  now  rise  in  bub- 
bles, through  the  funnel,  into  the  upper  jar,  and  will  expel  the  water  from  it  into 
the  trough. 

3.  Let  one  of  the  jars,  provided  with  a stop-cock  at  the  top,  be  placed  full  of 
air  on  the  shelf  of  the  trough.  Screw  upon  it  an  empty  bladder;  open  the 
communication  between  the  jar  and  the  bladder,  and  press  the  former  into  the 
water,  (Fig.  94.)  The  air  will  then  pass  into  the  bladder,  till  it  is  filled;  and 
when  the  bladder  is  removed  from  the  jar,  and  a pipe  screwed  upon  it,  the  air 
may  be  again  transferred  into  a jar  inverted  in  water. 

4.  For  the  purpose  of  transferring  gases  from  a wide  vessel  standing  over  wa- 
ter, into  a small  tube  filled  with  and  inverted  in  mercury,  the  following  contriv-  Cavern- 
ance  of  Cavendish  may  be  used.  A tube,  eight  or  ten  inches  long,  and  of  very  ^1SVS  , 
small  diameter,  is  drawn  out  to  a fine  bore,  and  bent  at  one  end,  so  as  to  resem-  method. 
ble  the  italic  letter  l.  The  point  is  then  immersed  in  quicksilver,  which  is 
drawn  into  the  tube  till  it  is  filled,  by  the  action  of  the  mouth.  Placing  the  finger 

over  the  aperture  at  the  straight  end,  the  tube  is  next  conveyed  through  the  wa- 
ter, with  the  bent  end  uppermost,  into  an  inverted  jar  of  gas.  When  the  finger 
is*  removed,  the  quicksilver  falls  from  the  tube  into  the  trough,  or  into  a cup 
placed  to  receive  it,  and  the  tube  is  filled  with  the  gas.  The  whole  of  the  quick- 
silver, however,  must  not  be  allo  wed  to  escape  ; but  a column  must  be  left,  three 
or  four  inches  long,  and  must  be  kept  in  its  place  by  the  finger.  Remove  the 
tube  from  the  water  ; let  an  assistant  dry  it  with  blotting  paper  ; and  introduce 
the  point  of  the  bent  end  into  the  aperture  of  the  tube  standing  over  quicksilver. 

On  withdrawing  the  finger  from  that  aperture  which  is  now  uppermost,  the 
pressure  of  the  column  of  quicksilver,  added  to  the  weight  of  the  atmosphere, 
will  force  the  gas  from  the  bent  tube  into  the  one  standing  in  the  mercurial 
trough.* 

346.  For  the  transference  of  small  quantities  of  gas  from  one  vessel  to  another,  , . 
the  instrument  contrived  by  Pepys  is  convenient.  It  is  made  t>f  a piece  of  glass  ^uUienT" 
tube,  about  half  an  inch  in  diameter  and  five  inches  long,  attached  Fig.  no.  ^or  lrans_ 
to  a piece  of  smaller  diameter,  which,  after  bending  as  in  Fig.  112,  q ference 

terminates  in  a chamber  at  a,  which  being  cylindrical  for  the 
greater,  part  of  its  length,  terminates  in  a capillary  tube  and  aper- 
ture. A small  piston,  rendered  air-tight  by  tow  and  tallow,  is 
fitted  into  the  cylindrical  tube  ; it  is  moved  by  a rod  and  ring,  the 
rod  passing  through  a box  which  closes  the  upper  aperture  of  the  A 
instrument,  but  which  should  not  be  air-tight.  A portion  of  mer-  ^/j  ^ 

cury  is  placed  above  the  piston,  the  space  between  it  and  the  W JJ 

capillary  opening  of  the  chamber,  is  filled  with  the  same  metal 
when  the  piston  is  in  the  position  depicted.  Upon  raising  the  piston,  the  mer- 
cury follows  it,  and  descends  into  the  chamber  a,  the  space  left  by  it  being  im- 
mediately filled  with  the  air  or  gas  Which  has  access  to  the  capillary  opening. 

The  rod  has  a graduation  upon  it,  by  which  it  is  known  when  a tenth  of  a 
cubical  inch  of  air  has  entered  the  chamber.  F.  340. 

347-  The  manipulation  with  jars  and  glasses  is  comparatively  easy  to  that 
which  occurs  in  transference  from  them  to  tubes,  or  from  tubes  to  each  other.  Manipula- 
One  circumstance  with  tubes  which  occasions  difficulty,  in  addition  to  the  nar- 11011  Wlth 
rowness  of  their  mouths,  is,  their  contracted  capacity  within,  by  which  the  easy  tu°es. 


* In  collecting  and  transferring  gases  over  quicksilver,  especially  where  the  quick- 
silver is  impure  or  dirty,  the  gas  will  escape  on  the  outside  of  the  jar,  there  being  so 
little  adhesion  between  the  quicksilver  and  the  glass;  this,  I have  found,  may  be 
partially  guarded  against  by  slightly  smearing  the  edge  of  the  jar  with  pomatum.  W. 

15 


114 


Chap.  IL 


Transfer- 
ring from 
large  to 
small  tubes, 


From  jars. 


Removing 
tubes  con- 
taining gas 


Specific 

gravities. 


« Apparatus  and  Manipulation. 

passage  of  a bubble  of  gas  upwards,  and  water  downwards,  at  the  same  time,  is 
interfered  with  ; this  effect  is  greatest  in  tubes  of  the  smallest  diameters.  No 
great  difficulty  will  occur  in  the  transference  of  gas 
from  a tube  to  another  that  is  wider.  (Fig.  113.)  The 
second  tube  is  to  be  filled  in  the  usual  manner  with 
water,  and  held  in  the  well  of  the  trough,  in  a consi- 
derably inclined  position  : the  tube  containing  the  gas 
is  to  be  brought  near  it,  the  upper  edge  of  its  mouth 
inserted  as  it  were  into  the  mouth  of  the  first,  and  then 
its  position  slowly  altered,  until  the  gas  passing  to- 
wards the  mouth  be  gradually  delivered  in  distinct 
bubbles  into  the  first  tube.  During  this  transfer,  the 
should  be  retained  as  much  as  possible  within  the  first ; the  latter  should  not  be 
raised  to  a perpendicular  position,  but  be  considerably  inclined,  for  then  the 
edges  of  its  mouth  meet  better  with,  and  are  adapted  to,  those  of  the  second  tube, 
so  as  to  oonfine  the  gas,  and  the  motion  of  the  bubbles  is  less  sudden  and  less 
subject  to  derangement.  Occasionally  it  is  advantageously  placed  in  almost  a 
horizontal  position,  its  closed  extremity  being  but  little  raised.  One  bubble  of 
gas  should  be  allowed  to  rise  to  some  height  in  the  tube  before  another  is  permit- 
ted to  follow. 

348.  When  the  delivering  tube  is  larger  than  the  receiving  tube,  more  care  is 
required  in  the  transfer.  The  first  tube  should  be  inclined  as  before,  and  the 
upper  edge  of  the  mouth  of  the  second  placed  within  it,  and  to  assist  in  uniting 
as  it  were  the  two  tubes  for  the  moment,  the  finger  and  thumb  of  the  left  hand 
(which  holds  the  receiving  tube)  should  be  applied  at  the  sides  of  the  junction,  so 
as  to  confine  the  gas  and  prevent  its  escape  laterally.  For  this  purpose,  and  ge- 
nerally in  tube  transference,  the  tube  is  best  held  in  the  hand,  with  its  open  ex- 
tremity passing  out  between  the  thumb  and  fore  finger,  so  that  when  sustained 
in  the  water  in  an  inclined  position  the  back  of  the  hand  may  be  upwards,  the 
hand  being  as  it  were  over  the  vessel ; the  tube  is  then  easily  supported  by  the 
two  or  three  last  fingers  of  the  hand,  and  the  fore  finger  and  thumb  are  left  at 
liberty  to  guide  the  mouths  of  the  vessels  or  to  close  the  lateral  opening,  as  has 
been  just  described.  At  other  times  it  may  be  held  as  a pen  is  retained  in  the 
hand,  the  mouth  being  confined  and  guided  between  the  thumb  and  two  fore 
fingers.  The  tubes  should  at  all  times  be  retained  by  a light  and  easy,  though 
secure  hold,  and  not  in  a stiff'  rigid  manner,  and  the  arms  may  often  be  allowed 
to  rest  with  advantage  on  the  edge  of  the  trough,  whilst  the  hands  are  immersed 
in  the  water. 

349.  An  intermediate  lipped  glass  should  be  used  for  the  transference  of  gas 
from  a large  jar  to  a lube.  The  tube  being  filled  with  water  is  to  be  held  under 
the  surface  as  before  described  (347) ; the  lip  is  to  be  introduced  into  it,  the  junc- 
tion made  by  the  fingers  if  necessary,  as  in  the  former  case,  and  the  gas  allowed 
to  pass  in  distinct  bubbles.  It  will  be  found  easier  to  transfer  from  a glass  that 
is  from  a third  to  five-sixths  full  of  gas,  than  from  one  containing  more  or  less. 
When  a glass  is  nearly  empty,  it  is  often  exceedingly  difficult  to  transfer  from  it 
into  a narrow  tube.  Advantage  may  therefore  occasionally  be  taken  of  the  cir- 
cumstance above  mentioned,  to  replenish  the  glass  with  gas. 

350.  Tubes  containing  gases  are  easily  transferred  from  one  trough  to  another, 
or  to  other  situations,  merely  by  closing  their  mouths  with  the  finger  or  thumb, 

• and  carrying  them  to  the  required  situation.  The  student  should  very  early  at- 
tain the  habit  of  closing  the  mouth  of  a tube  by  the  finger  with  facility  and  secu- 
rity. The  accurate  manipulation  of  gas  in  tubes,  so  that  none  shall  escape  and 
be  lost,  is  often  essential  in  experiments  of  research,  where  only  small  portions 
of  gas  are  evolved  for  examination  as  to  many  of  its  properties.  F.  326. 

Section  III.  Methods  of  estimating  Specific  Gravities. 

351.  Water  has  been  fixed  upon  as  the  standard  of  comparison  in  estimating 
specific  gravities;  and  its  specific  gravity  has  been  called  1. 

352.  In  all  experiments  for  ascertaining  the  specific  gravities  of  different  sub- 
stances, particularly  of  gases,  great  attention  must  be  paid  to  the  temperature,  as 
their  volume  varies  with  the  degree  of  heat  to  which  they  are  exposed. 


Fig.  1 .3. 


mouth  of  the  second  tube 


115 


Specific  Gravity. 


353.  To  find  the  specific  gravity  of  a solid  body  heavier  than  water, — First,  Sect.  III. 

weigh  the  solid  in  air;  then  weigh  it  in  water  by  a hy-  Fig.  Ilf  ~ ^ 

drostatic  balance  in  tbe  manner  represented  in  Fig.  114,  gmvitvof 

using  a very  fine  thread,  or  a hair  to  suspend  it  from  the  H solids^ 

bottom  of  one  of  the  scales.  The  difference  in  the 
results  will  express  the  weight  of  a quantity  of  water 
equal  in  bulk  to  the  solid  whose  specific  gravity  is  to  be 
determined,  and  the  following  proportion  will  give  its 
specific  gravity  in  relation  to  water  : As  the  weight  of 
the  water  equal  in  bulk  to  that  of  the  solid  is  to  the 
weight  of  the  solid  itself,  so  is  the  specific  gravity  of  wa- 
ter to  the  specific  gravity  of  the  solid.  Thus, 

If  the  solid  weigh  100  grains  in  air,  and  60  grains  in  wa- 
ter, then  100 — 60,  or  40  : 100  : : L:  2.5.  The  specific 
gravity  of  the  solid  is  therefore  2.5  compared  with  that  of  water. 

354.  If  the  solid  should  be  lighter  than  water,  a more  complicated  process  will  Of  light 
be  necessary.  Attac:h  to  the  light  solid  by  a slender  thread  another  body  of  such  bodies, 
a weight  that  when  tied  together  they  shall  sink  in  water,  having  previously 
weighed  the  heavier  solid  in  water,  and  each  in  air;  then  weigh  them  together 

in  water,  and  from  the  difference  between  their  weight  in  water  and  their  weight 
in  air,  subtract  the  difference  between  the  weight  of  the  heavy  solid  in  air  and 
its  weight  in  water  ; the  remainder  will  show  the  weight  of  a quantity  of  water 
equal  in  bulk  to  the  light  body,  and  we  can  then  find  its  specific  gravity  in  the 
way  directed  above.  Thus, 

If  the  weight  in  air  of  the  light  solid  be  10  and  of  the  heavy  solid  20  ; and  if  the 
weight  of  the  heavy  solid  in  water  be  18,  and  of  the  two  together  7, — then 
From  their  weight  in  air,  . . . . 20  -f- 10  = 30 

Substract  their  weight  in  water,  ...  7 


And  from  this  substract  20 — 18=  2 


23 

2 


The  remainder 


21 


expresses  the  weight  of  a quantity  of  water  equal  in  bulk  to  the  light  solid,  and 
the  following  proportion  will  give  us  its  specific  gravity, 

21  : 10  : : 1.  : 0.47619, — the  specific  gravity  of  the  lighter  solid. 

355.  Where  a hydrostatic  balance  cannot;  be  procured,  the  following  method 

may  be  adopted  : Weigh  the  solid  and  put  it  into  a vessel  full  of ! water,  the  Another 
weight  of  which  with  the  water  is  known;  the  solid  will  displace  a quantity  of  method, 
water  equal  in  bulk  to  its  own ; weigh  the  vessel  again,  having  either  taken  out 
the  solid  body,  or  put  an  equal  weight  in  the  opposite  scale ; — the  difference  be- 
tween the  present  weight  of  the  vessel  and  its  former  weight  will  express  the 
weight  of  a quantity  of  water  equal  in  bulk  to  the  solid  body,  from  which,  by 
the  same  proportion  as  in  the  former  instances,  we  can  estimate  the  specific  gravity 
of  the  solid  body.  Thus,  if  the  vessel  when  full  of  water  weighed  1000,  and 
after  some  of  the  water  had  been  displaced  by  the  solid  body  and  the  solid  re- 
moved, or  a counterpoise  placed  in  the  opposite  scale,  it  weighed  900  grains, — 

100  grains  of  water  were  displaced  by  the  solid  body — and  if  the  solid  body  in  air 
weighed  300  grains,  then  the  following  proportion  will  give  its  specific  gravity  : 

100  : 300  : : 1 : 3. 

356.  If  the  solid  body  be  soluble  in  water,  some  other  fluid,  as  oil,  alcohol, 

ether,  or  a saturated  solution  of  the  substance  itself  must  be  used,  its  specific  gra-  of  soluble 
vity  being  previously  ascertained.  We  must  first  find  the  specific  gravity  of  the  kocqes 
solid,  considering  the  fluid  used  as  a standard  of  comparison,  and  making  the  ' 

number  representing  its  specific  gravity  the  third  term  in  the  proportion,  in  the 
same  manner  as  when  water  is  used ; and  then,  by  simple  proportion,  reduce 
the  product  to  the  standard  of  water.  Thus,  if  the  specific  gravity  of  the  fluid 
used  be  1.2,  and,  considering  it  as  a standard  of  comparison,  the  specific  gravity 
of  the  solid  be  1.8,  then  the  following  proportion  will  give  us  its  real  specific 
gravity  : 

1.2  : 1.8  : : 1.  : 1.5. 

357.  When  the  substance,  the  specific  gravity  of  which  is  to  be  ascertained,  is  Of  pow- 
in  the  form  of  a powder,  the  following  method,  recommended  by  Leslie,  will  ders, 
be  found  most  convenient.  (Fig.  115.)  Take  a glass  tube  b /,  three  feet  in 


116 


Chap.  II. 


Ofliquids. 


Areometer. 


Lovi’s 

heads. 


Of  Gases. 


Apparatus  and  Manipulation. 


length,  and  open  at  both  ends.  The  wide  part  b e is  to  be  about  Fig-  115. 

of  an  inch  in  diameter,  and  the  narrow  part  c / about  com-  flO 
municating  with  each  other  by  a very  small  aperture  at  c,  which  n — 

allows  air  to  pass,  but  is  sufficiently  small  to  prevent  any  powder  0 

from  going  through.  The  upper  opening  at  b is  to  be  ground,  so  that 
it  can  be  accurately  closed  by  a glass  plate  a.  The  substance  whose 
specific  gravity  is  to  be  determined,  is  put  into  the  wide  part  of  the 
tube  b c , which  is  then  to  be  placed  in  a wider  tube  containing  mer- 
cury  g , making  it  descend  till  the  fluid  metal  shall  have  reached  the  , 
aperture  at  c.  Then  fix  the  cover,  making  it  air-tight  with  a very  a 

small  quantity  of  lard,  and  lift  it  perpendicularly  out  of  the  mercury,  ^ 

till  the  aperture  at  c shall  have  been  raised  above  the  surface  of  the 
mercury  in  the  tube  to  a height  exactly  equal  to  half  the  height  of  the  /. 
barometer  at  the  time  the  experiment  is  made,  and  mark  the  point  at  J 
which  the  smaller  tube  is  cut  by  the  fluid,  w hich  we  shall  suppose  in  the  present 
instance  to  bo  d.  The  air  within  that  part  of  the  tube  in  which  the  powder  has 
been  placed  being  now  subjected  to  the  pressure  of  only  half  an  atmosphere,  it 
expands  to  double  its  former  volume,  one  half  still  remaining  within  b c,  w hile 
the  rest  occupies  c d,  the  space  it  includes  representing  therefore  the  total  bulk  of 
air  included  at  first  along  with  the  powder  in  b c at  the  ordinary  pressure.  The 
powder  is  now  withdrawn,  and  the  process  repeated  with  b c full  of  air  only, 
when  it  is  obvious  that  the  mercury  will  not  stand  so  high  within  the  tube  cf  as 
before,  and  supposing  it  to  rise  only  to  e,  then  the  space  c c will  contain  a quan- 
tity of  expanded  air,  equal  in  bulk  exactly  to  wrhat  w ould  be  contained  in  b c be- 
fore lifting  up  the  tube.  Since  c e then  represents  a space  exactly  equal  to  that 
within  b c,  and  c d a space  equal  to  the  volume  of  air  in  be  when  the  powder  wras 
in  it,  then  d e}  the  difference  between  them,  shows  the  spaee  occupied  by  the 
powder  when  it  was  in  b c.  In  this  manner,  then,  we  are  enabled  to  find  out  a 
space  exactly  equal  in  bulk  to  that  of  the  solid  matter  in  the  pow’der,  and  if  the 
stem  be  graduated  so  as  to  express  in  grains  the  quantity  of  water  which  it  can 
contain,  we  have  only  to  weigh  the  powder  in  air  and  compare  its  weight  with 
that  of  the  equal  bulk  of  water  to  ascertain  its  specific  gravity. 

358.  Take  a bottle  of  a known  weight,  fill  it  with  distilled  water,  and  weigh 
it  carefully;  then  pour  out  the  water,  and  after  drying  the  bottle,  fill  it  with  the 
liquid  to  be  tried.  The  following  proportion  will  give  its  specific  gravity  : As 

the  weight  of  the  distilled  water  is  to  the  weight  of  the  liquid,  so  is  1 to  the  spe- 
cific gravity  required.  Thus,  if  the  weight  of  the  distilled  water  be  300  grains, 
and  that  of  the  liquid  600,  the  following  is  the  proportion  wre  must  use  : — 

300  : 600  : : 1.  : 2. 

The  areometer  is  a convenient  instrument  for  ascertaining  the  specific 
gravities  of  liquids.  It  consists  of  a long,  straight,  graduated  stem,  on  which 
numbers  are  marked  at  the  points  to  which  the  instrument  sinks  in  liquids  of  the 
specific  gravities  marked  at  these  points.  Thus,  in  distilled  water  it  will  sink  to 
1,  and  in  nitric  acid  to  1.48.  It  is  made  of  different  materials  according  to  the 
nature  of  the  liquids  whose  specific  gravities  are  to  be  ascertained  with  it. 

Lovi’s  beads  are  also  very  useful  for  ascertaining  the  specific  gravities  of 
liquids.  These  are  small  balls  made  of  glass,  with  numbers  marked  on  them  in- 
dicating the  specific  gravity  of  those  liquids  in  which  they  float  without  any  ten- 
dency either  to  sink  or  rise  to  the  top.  Those  that  float  on  the  surface  show 
that  the  liquid  has  a greater  specific  gravity  than  the  number  marked  on  them 
expresses,  while  those  that  sinlv  indicate  tiie  reverse,  being  heavier  than  an  equal 
bulk  of  the  fluid. 

350.  Atmospheric  air  is  taken  as  a standard  of  comparison  in  estimating  the 
specific  gravitv  of  gases,  and  represented  by  the  number  1.  Their  specific  gra- 
vities are  found  out  in  the  same  manner  as  those  of  other  substances,  viz.  by 
comparing  the  w eight  of  equal  bulks  of  them  and  of  the  substance  which  is  taken 
as  a standard  of  comparison. 

For  this  purpose,  a flask  provided  with  a stop-cock  is  accurately  weighed  and 
attached  to  an  air-pump  or  exhausting  syringe,  which  is  worked  in  the  usual 
manner  ; and,  wffien  the  gas  whose  specific  gravity  is  to  be  tried  has  no  action  on 
atmospheric  air,  it  is  not  necessary  to  exhaust  it  to  a very  great  degree.  The 
stop-cock  fixed  to  the  flask  is  then  turned,  wThen  it  is  weighed  again  to  ascertain 
the  quantity  of  air  extracted.  It  is  then  screwed  on  to  a jar  (placed  over  a pneu- 
matic trough)  containing  the  gas  whose  specific  gravity  is  to  be  determined,  and 
on  opening  the  stop-cock,  a quantity  of  gas  is  forced  by  the  pressure  of  the  atmos- 
phere into  the  flask,  exactly  equal  in  bulk  to  the  air  which  had  been  withdrawn, 
if  the  jar  be  depressed  in  the  liquid  till  it  shall  be  level  both  within  and  without. 


Liquefaction  of  Gases.  117 

If  the  flask  be  then  detached  from  the  jar,  it  is  obvious  that  by  weighing  it  again  Sect-  lit. 
we  can  find  out  the  weight  of  a measure  of  gas  exactly  equal  in  bulk  to  that  of 
the  air  whose  weight  was  found  out  by  the  first  operation. 

For  example,  if  the  flask  should  weigh  570  grains  when  full  of  air,  and  560  Example, 
after  the  exhaustion,  then  the  quantity  of  air  which  has  been  withdrawn  weighs 
10  grains,  «, 

W eight  of  flask  with  air  .....  570  grains. 

Weight  of  flask  aftpr  exhaustion  ....  560  do. 

Weight  of  air  withdrawn,  . ...  10  do. 

And  if  it  shall  weigh  580  grains  after  admitting  an  equal  volume  of  the  gas 
whose  specific  gravity  is  to  be  determined,  then  it  must  be  twice  as  heavy,  or  its 
specific  gravity  must  be  twice  as  great  as  that  of  atmospheric  air. 

Weight  of  flask  with  gas  . . . . . . 580  grains. 

Weight  of  flask  after  exhaustion,  , 560  do. 

Weight  of  gas  introduced 20  do. 

When  the  gas  whose  specific  gravity  is  to  be  ascertained  acts  chemically  on 
atmospheric  air,  the  latter  must  be  withdrawn  as  completely  as  possible  by  re- 
peated exhaustions,  filling  it  after  each  with  some  gas  which  is  not  affected  by 
the  other,  and  then  proceeding  in  the  usual  manner. 

360.  In  operating  with  gases,  it  is  also  necessary  to  attend  to  the  pressure  of 
the  atmosphere  as  indicated  by  the  barometer,  and  the  quantity  of  watery 
vapour  which  thby  may  contain.  Formulas  have  been  given  for  making  correc- 
tions when  the  barometer  is  not  at  the  point  adopted  as  the  standard  of  compari- 
son, and  for  the  quantity  of  watery  vapour  which  the  gases  may  contain,  for 
which  see  Faraday’s  Chem.  Manip.  375,  and  Turner,  48. 

361.  It  may  be  necessary,  to  remark,  that  when  the  specific 
gravity  of  a gas  is  ascertained,  and  no  variation  in  the  pressure  of 
the  atmosphere  of  any  consequence  takes  place  in  the  short  space  of 
time  necessary  for  this  purpose,  and  equal  bulks  of  air  and  the  gas 
whose,  specific  gravity  is  to  be  found  out  having  been  weighed  in  this 
manner,  precisely  under  the  same  circumstances  with  respect  to 
pressure,  no  corrections  on  this  account  are  required.* 

362.  Many  operations  upon  the  gases  may  be  performed  in  appa-Tub 
ratus  formed  partly  or  altogether  of  glass  tube,  for  a particular  de-ratus.  P 
scription  of  which,  the  precautions  to  be  attended  to  in  taking  specific 
gravities,  and  many  other  details,  the  student  is  referred  to  Faraday’s 
Chemical  Manipulation. 

363.  The  experiments  of  Davy  and  Faraday  have  shown  that 
many  substances,  which  had  previously  been  known,  when  uncom- 
bined, only  as  gases,  may  be  obtained  in  a liquid  state  by  generating 
them  under  pressure. 

When  thus  compressed,  a very  moderate  heat  is  sufficient  to  make  Liquefac- 
them  boil  ; and  on  the  removal  of  pressure  they  re-assume  the  elas-  tion  of 
tic  form,  most  of  them  with  such  violence  as  to  cause  a report  like  gases- 
an  explosion,  and  others  with  the  appearance  of  brisk  ebullition. 

An  intense  degree  of  cold  is  produced  at  the  same  time,  in  conse- 
quence of  caloric  becoming  latent. 

The  process  for  condensing  the  gases  consists  in  exposing  them  Process, 
to  the  pressure  of  their  own  atmospheres.! 

The  materials  for  producing  them  are  put  into  a strong  glass  tube  about  eight 
inches  long,  which  is  afterwards  sealed  hermetically  ; then,  being  softened  in  the 
flame  of  a lamp,\  at  about  five  inches  from  the  closed  end,  it  is  to  be  bent,  not 
sharply,  but  obtusely  and  roundly,  until  the  two  limbs  make  an  angle  of  about 
130°  or  140°.  The  gas  is  generated,  if  necessary,  by  the  application  of  heat, 


* Reid’s  Elements  of  Pr act.  Chem. 


t See  Carbonic  Acid. 


]18 


Chap.  III. 

Pressures 

required. 


Discovery. 


How  ob* 
la  ined. 


Theory. 


Oxygen. 


and  when  the  pressure  becomes  sufficiently  great,  the  liquid  forms  and  collects  in 
the  free  end  of  the  tube,  which  is  kept  cool  to  facilitate  the  condensation.* 

The  pressure  required  to  liquefy  the  gases  is  very  variable,  as  will 
appear  from  the  following  table  of  results  obtained  by  Faraday  : 


Sulphurous  acid  gas  . 
Sulphuretted  hydrogen  gas 
Carbonic  acid  “ 

Chlorine  “ 

Nitrous  oxide  “ 

Cyanogen  “ 

Arnmoniacal  “ 

Muriatic  acid  w 


Atmospheres. 

2 at  45°  F 

17  “ 50° 

. 36  “ 32° 

4 « 60° 

. 50  “ 45° 

3,6  “ 45° 

6,5  “ 50° 

. 40  “ 50° 


CHAPTER  III. 

INORGANIC  CHEMISTRY. 

Section  I.  Oxygen. 

Sip  lib.  Sp.  Gr.  Equip. 

O 1.1024  air  =1  By  Vol.  50. 

1C. 00  Hyd.=t  “ Wgt.  8. 

364.  Oxygen  has  never  been  obtained  in  a state  of  complete  sepa- 
ration. In  the  state  of  gas,  it  was  discovered  in  1774  by  Priestley, 
who  gave  it  the  name  of  dephlogisticated  air.  It  was  called  Empy- 
real air , by  Scheele,  and  Vital  air  by  Condorcet. 

365.  It  may  be  obtained  from  various  substances.  1.  From  the 
black  or  peroxide  of  manganese,  heated  to  redness  in  a gun-barrel, 
or  in  an  iron  retort  (Fig.  89)  ; or  from  the  same  oxide,  heated  by  a 
lamp  in  a retort,  (Fig.  96,  c,)  or  gas  bottle,  (Fig.  87,)  with 
half  its  weight  of  strong  sulpuric  acid.  One  pound  of  manganese  is 
capable  of  furnishing  from  40  to  50  wine  pints  of  gas.  But  as  man- 
ganese is  often  contaminated  with  a small  proportion  of  carbonate  of 
lime,  it  is  advisable,  before  using  it,  to  wash  it  with  hydrochloric 
acid  diluted  with  15  or  20  parts  of  water;  then  with  distilled  water; 
and  afterwards  to  dry  it  at  a moderate  heat. 

To  understand  the  theory  of  these  processes,  it  is  necessary  to  bear 
in  mind  the  composition  of  the  three  following  oxides  of  manganese  : 
Manganese.  Oxygen. 

Protoxide  . 27.7  or  1 equiv.  -}-  6 . =35  7 

Sesquioxide  27  7 . . -f  12  . =39.7 

Peroxide  27.7  . . — 16  . =43  7 

On  applying  a red  heat  to  the  last,  it  parts  with  half  an  equivalent 
of  oxygen,  and  is  converted  into  the  sesquioxide.  Every  43.7  grains 
of  the  peroxide  will,  therefore,  lose,  if  quite  pure,  4 grains  of  oxygen, 
or  nearly  12  cubic  inches ; and  one  ounce  will  yield  about  12S  cubic 
inches  of  gas.  The  action  of  sulphuric  acid  is  different.  The  per- 
oxide loses  a whole  equivalent  of  oxygen,  and  is  converted  into  prot- 
oxide, which  unites  with  the  acid,  forming  a sulphate  of  the  protoxide 
of  manganese.  Every  43.7  grains  of  peroxide  must  consequently 
yield  8 grains  of  oxygen  and  35.7  of  protoxide,  which  by  uniting 
with  one  equivalent  (40.1)  of  the  acid,  forms  75.8  of  the  sulphate. 
The  first  of  these  processes  is  the  most  convenient  in  practice. 

♦These  experiments  are  dangerous  and  should  not  be  undertaken  without  attending 
to  the  directions  given  by  Faraday  tn  Sect.  xvi.  Chem.  Manip. 


119 


Properties  and  Effects. 

2.  From  various  other  oxides,  as  will  be  hereafter  mentioned. 

3.  From  nitrate  of  potassa  (common  saltpetre)  made  red-hot  in  a 
gun-barrel,  or  in  a coated  earthen  retort. 

4.  From  the  salt  called  chlorate  of  potassa.  For  this  purpose,  the 
salt  should  be  put  into  a retort  of  green  glass,  or  of  white  glass  made 
without  lead,  and  be  heated  nearly  to  redness.  It  first  becomes  liquid, 
though  quite  free  from  water,  and  then,  on  increase  of  heat,  is  wholly 
resolved  into  pure  oxygen  gas,  which  escapes  with  effervescence, 
and  into  a white  compound,  called  chloride  of  potassium,  which  is 
left  in  the  retort.  The  composition  of  the  chloric  acid  and  potassa 
which  constitute  the  salt,  is  stated  below ; — 

Chlorine  . 35.42  or  1 eq.  Potassium  . 39.15  or  1 eq. 

Oxygen  . 40  or  5 eq.  Oxygen  . 8 or  1 eq. 

Chloric  acid  75.42  or  1 eq.  Potassa  . 47.15  or  1 eq. 

Hence  the  oxygen  which  passes  over  from  the  retort,  is  derived 
partly  from  the  potassa  and  partly  from  the  chloric  acid  ; while  chlo- 
rine and  potassium  enter  into  combination.  Thus  are  122.57  grains 
of  the  chlorate  resolved  into  74.57  grains  of  chloride  of  potassium, 
and  48  grains,  or  about  161  cubic  inches,  of  pure  oxygen. 

366.  Oxygen  gas  is  insipid,  colourless,  and  inodorous.  It  is  so  Properties 
sparingly  absorbed  by  water,  that  when  agitated  in  contact  with  it,  °xyoei1 
no  perceptible  diminution  takes  place.  100  cubical  inches  at  mean  s 
temperature  and  pressure,  weigh  34.1872  grains.  It  refracts  the  Effect  of 
rays  of  light  less  than  any  other  gas.  When  suddenly  and  strongly  s°<^res’ 
compressed,  heat  is  evolved,  and  a luminous  appearance  observed 

from  the  combustion  of  the  oil  with  which  the  compressing  tube  is 
lubricated.* 

367.  It  is  a powerful  supporter  of  respiration  and  combustion.  Supports 
No  animal  can  live  in  an  atmosphere  which  does  not  contain  a cer-  resPiratlon 
tain  portion  of  uncombined  oxygen  ; for  an  animal  soon  dies  if  put  Effect  on 
into  a portion  of  air  from  which  the  oxygen  has  been  previously  re-  animals, 
moved  by  a burning  body.  It  may,  therefore,  be  anticipated  that 
oxygen  is  consumed  during  respiration.  Respiration  and  combus- 
tion have  the  same  effect.  An  animal  cannot  live  in  an  atmosphere 

which  is  unable  to  support  combustion  ; nor,  in  general,  can  a can- 
dle burn  in  air  which  contains  too  little  oxygen  for  respiration. 

It  is  singular  that,  though  oxygen  is  necessary  to  respiration,  in  a 
state  of  purity  it  is  deleterious.  When  an  animal  is  supplied  with 
an  atmosphere  of  pure  oxygen  gas,  no  inconvenience  is  at  first  per- 
ceived ; but  after  the  interval  of  an  hour  or  more,  the  circulation  and 
respiration  become  very  rapid,  and  the  system  in  general  is  highly 
excited.  Symptoms  of  debility  subsequently  ensue,  followed  by 
insensibility:  and  death  occurs  in  six,  ten,  or  twelve  hours.  On 
examination  after  death,  the  blood  is  found  highly  florid  in  every 
part  of  the  body,  and  the  heart  acts  strongly  even  after  the  breathing 
has  ceased. t 

The  absorption  of  oxygen  gas  by  the  blood,  and  the  change  of 
colour  that  results,  may  be  shown  by  passing  up  a little  dark  venous 
blood  into  a jar  filled  with  the  gas,  or  by  agitating  a portion  in  a 
phial  filled  with  it. 


*Thenard. 


+ Broughton. 


120 


Oxygen. 


chap,  hi.  All  combustible  bodies  burn  in  oxygen  gas  with  greatly  increased 
splendour. 

A lighted  wax  taper,  fixed  to  an  iron  wire,  and  plunged  into  a ves- 
sel of  this  gas,  burns  with  great  brilliancy.  (Fig.  116.)  If  the  taper  be 
blown  out,  and  let  down  into  a vessel  of  the  gas  while  the  snuff  re- 
mains red  hot,  it  instantly  rekindles,  with  a slight  explosion. 

A red-hot  bit  of  charcoal,  fastened  to  a copper  wire,  and  immersed 
in  the  gas  throws  out  beautiful  sparks. 

The  light  of  phosphorus  burning  in  this  gas,  is  exceed- 
ingly bright. 


Supports 

combus- 

tion. 

Exp. 


Combus- 
tion of 
phospho- 
rus, 


Exp. 


Let  the  phosphorus  be  placed  in  a small  hemispherical  tin  cup,  which  may  bo 
raised  by  means  of  a wire  stand,  (Fig.  117,)  two  or  three  inches  above  the  sur- 
face of  water  contained  in  a broad  shallow  dish.  Fill  a bell- 
shaped  receiver,  having  an  open  neck  at  the  top,  to  which  a 
stopper  is  ground,  with  oxygen  gas  ; and  as  it  stands  inverted 
in  water,  press  a circular  piece  of  pasteboard,  rather  exceeding 
the  jar  in  diameter,  over  its  mouth.  Cover  the  phosphorus 
instantly  with  the  jar  of  oxygen  gas,  retaining  the  pasteboard 
in  its  place,  till  the  jar  is  immediately  over  the  cup.  When 
this  has  been  skilfully  managed,  a very  small  portion  only  of  ^ 
the  gas  will  escape.  The  stopper  may  now  be  removed,  when 
the  water  will  rise  to  the  same  level  within  as  without  the  jar,  and  the  phospho- 
rus may  be  kindled  by  a heated  copper  wire.* 

Substitoto  for  the  phosphorus  a small  ball  formed  of  turnings  of  zinc,  in  which 
about  a grain  of  phosphorus  is  to  be  enclosed.  Set  fire  to  the  phosphorus  as  be- 

“ul  white 


fore.  'I’he  zinc  will  be  inflamed,  and  will  burn  with  a beautiful  white  light.  A 
Of  zinc  and  similar  experiment  may  be  made  with  metallic  arsenic,  which  may  be  moistened 
other  met-  with  spirit  of  turpentine.  The  filings  of  various  metals  may  also  be  inflamed,  by 
als,  placing  them  in  a small  cavity,  formed  in  a piece  of  charcoal,  igniting  the  char- 

coal, and  blowing,  on  the  part  containing  the  metal,  a stream  of  oxygon  gas  from 


Of  Iron. 


The  combustion  of  iron  or  steel  w ire  in  this  gas  is  remarkably  brilliant.  The 
wire  best  suited  for  this  experiment  is  the  fine  guitar  wire  ; it  should  he  doubled 
several  times  so  as  to  form  a bundle,  which  is  easily  done  by  passing  it  round 
two  nails  fixed  in  the  table  about  eighteen  inches  apart,  and  securing  the  bunch 
by  loosely  winding  the  last  turn  round  it.  Before  removing  it  from  the  nails,  the 
flame  of  a spirit  lamp  should  be  slowly  passed  along  the  wire  so  as  Fig.  118- 
to  give  a low  red  heat  to  every  inch,  and  thus  diminish  its  elasticity. 

When  cool,  the  bunch  is  to  be  coiled  round  a lube  or  rod  of  about 
ijths  of  an  inch  in  diameter.  Attach  one  end  to  a metallic  plate, t 
and  to  the  other  fix  a small  piece  of  cotton  dipped  in  melted  sulphur. 

A large  jar  (Fig.  118)  having  been  filled  with  the  gas,  remove  the 
stopple,  light  the  sulphur,  and  introduce  the  coil.t  The  iron  will 
burn  with  a most  brilliant  light,  throwing  out  a number  of  sparks, 
which  fall  to  the  bottom  ; if  a bottle  is  used  the  bottom  is  liable  to  be 
broken,  this  accident,  however,  may  frequently  be  prevented  by 
pouring  sand  into  the  bottle,  so  as  to  lie  about  half  an  inch  deep  on  the  bottom. 
By  directing  the  flame  of  a spirit  lamp,  by  means  of  a current  of  oxygen  gas, 
upon  a small  ball  of  lime,  the  most  intense  light  is  produced.  An  apparatus  lor 
this  purpose  has  been  described  by  Drummond  in  Edin  Jour,  of  Sci.  v.  31 9. § 
A little  of  Homberg's  pyrophorus,  a substance  to  be  hereafter  described, 
when  poured  into  a bottle  full  of  this  gas,  immediately  flashes  like  inflamed  gun- 
powder. 11.1.208. 

363.  During  every  combustion  in  oxygen  gas  it  suffers  a consi- 
bustionCOm"  ^era^e  diminution.il  The  fact  may  be  shown  by  the  combustion  of 

♦For  Hare's  apparatus  see  his  Compendium,  p.  103. 

+ The  wire  should  never  he  suspended  from  a cork,  as  it  may  take  fire. 
t Watch  springs,  partially  deprived  of  their  elasticity  in  the  same  way,  may  be  used. 
§ The  light  and  heat  of  an  Argatid  lamp  supplied  with  oxygen,  as  contrived  by 
Dr  C.  T.  Jackson,  are  intense.  See  plate  second. 

||  To  exhibit  this,  experimentally,  in  a manner  perfectly  free  from  all  sources  of  er- 
ror, would  require  such  an  apparatus  as  few  beside  adepts  in  chemistry  are  likely  to 
possess.  The  apparatus  required  for  this  purpose,  is  described  in  the  6th  chapter  of 
Lavoisier’s  Elements. 


Exp. 


Oxygen  di 
minisbes 


Theories  of  Combustion . 

phosphorus,  in  the  manner  which  has  been  already  described.  The 
first  effect  of  the  combustion  will  be  a depression  of  water  within  the 
jar  ; but  when  the  combustion  has  ceased,  and  the  vessel  has  cooled, 
a considerable  absorption  vvill  be  found  to  have  ensued.* 

In  this  process  a white  dense  vapour  is  produced,  which  condenses 
on  the  inner  surface  of  the  jar  in  solid  flakes.  This  substance  has 
strongly  acid  properties  ; and,  being  formed  by  the  union  of  oxygen 
with  phosphorus,  is  termed  the  phosphoric  acid.  In  the  instance  of 
charcoal,  though  that  substance  undergoes  combustion,  no  absorption 
ensues  ; because,  as  will  appear  in  the  sequel,  the  product  is  a gas, 
occupying  exactly  the  same  bulk  as  the  oxygen  gas  submitted  to  ex- 
periment. 

369.  The  phenomena  of  combustion  were  referred  by  Stahl  and 
his  associates,  to  a peculiar  principle  which  they  called  phlogiston ; 
it  was  supposed  to  exist  in  all  combustibles,  and  combustion  was  said 
to  depend  upon  its  separation  ; but  this  explanation  was  absurdly  at 
variance  with  the  well  known  fact,  that  bodies  during  combustion 
increase  in  weight. 

370.  All  bodies,  by  combustion  in  oxygen  gas,  acquire  an  addi- 
tion to  their  weight ; and  the  increase  is  in  proportion  to  the  quantity 
of  gas  absorbed,  viz.  about  one  third  of  a grain  for  every  cubic  inch 
of  gas. — To  prove  this  by  experiment,  requires  a complicated  appa- 
ratus. But  sufficient  evidence  of  this  fact  may  be  obtained  by  the 
following  very  simple  experiment. 

Fill  the  bowl  of  a common  tobacco  pipe,  with  iron  wire  coiled  spirally,  and  of 
known  weight : let  the  end  of  the  pipe  be  slipped  into  a brass  tube,  which  is 
screwed  to  a bladder  filled  with  oxygen  gas : heat  the  bowl  of  the  pipe,  and  its 
contents,  to  redness  in  the  fire,  and  then  force  through  it  a stream  of  oxygen  gas 
from  the  bladder.  The  iron  wire  will  burn  ; will  be  rapidly  oxidized  ; and  will 
be  found,  when  weighed,  to  be  considerably  heavier  than  before.  When  com- 
pletely oxidized  in  this  mode,  100  parts  of  iron  wire  gain  an  addition  of  about  30. 

371.  After  the  discovery  of  oxygen  gas,  it  was  adopted  by  Lavoi- 
sier as  the  universal  supporter  of  combustion.  The  basis  of  the  gas 
was  supposed  to  unite  to  the  combustible,  and  the  heat  and  light 
which  it  before  contained  in  the  gaseous  state,  were  said  to  be 
evolved  in  the  form  of  flame.  But  in  this  case,  several  requisites  are 
not  fulfilled  ; the  light  depends  upon  the  combustible,  and  not  upon 
the  quantity  of  oxygen  consumed  ; and  there  are  very  numerous  in- 
stances of  combustion,  in  which  oxygen,  instead  of  being  solidified, 
becomes  gaseous  during  the  operation  ; and,  lastly,  in  others,  no 
oxygen  whatever  is  present.  Combustion,  therefore,  cannot  be 
regarded  as  dependent  upon  any  peculiar  principle  or  form  of  matter. 

Berzelius,  in  adopting  the  electro-chemical  theory,  regards  the 
heat  of  combination  as  an  electrical  phenomenon,  believing  it  to 
arise  from  the  oppositely  electrical  substances  neutralizing  one  ano- 
ther, in  the  same  manner  as  the  electric  equilibrium  is  restored  during 
the  discharge  of  a Leyden  jar.  There  are,  indeed,  strong  grounds 
for  believing  that  electrical  action  is  an  essential  part  of  every  che- 
mical change,  and  it  is  probable  that  the  heat  developed  during  the 
latter  may  be  due  to  the  former ; but  this  part  of  science  is  as  yet 
too  imperfect  for  indicating  the  precise  mode  by  which  the  effect  is 


* Thq^e  persons  who  are  possessed  of  a mercurial  apparatus  may  repeat  this  expe- 
riment in  a less  exceptionable  manner,  as  described  in  Henry’s  Chemistry,  l.  210. 

16 


121 


Sect.  I. 


Stahl’s  idea 
of  combus- 
tion. 


Bodies  in- 
crease in 
weight. 


iXp. 


Theory  of 
Lavoisier, 


Insuffi- 

cient. 


Berzelius’ 

view. 


122 


Hydrogen , 


Chap  in.  produced.  The  heat  emitted  during  combustion  varies  with  the  na- 
ture of  the  material.*  T.  157. 

Products.  372.  The  substances,  capable  of  uniting  with  oxygen,  afford  acids 

and  oxides . 

373.  The  name  oxygen,  from  acid , and  yew&w  I generate , 

was  proposed  by  Lavoisier,  from  the  supposition  that  it  was  the  sole 
Oxygen  not cause  °f  acidity.  But  oxygen  is  not  essential  to  the  acidity  of  a 
essential  to  compound,  for  some  bodies  are  rendered  acid  by  union  with  chlorine, 
acidity.  others  by  hydrogen  ; and  the  theory  of  Lavoisier  which  consid- 
ered oxygen  as  the  essential  principle  of  acidity,  can  no  longer  be 
received  as  correct. 

In  many  instances,  a combustible  body,  which  affords  an  acid 
when  united  with  a certain  quantity  of  oxygen,  gives  an  oxide  when 
combined  with  a less  quantity ; and  the  acid  may  be  brought  back  to 
the  state  of  an  oxide  by  separating  part  of  its  oxygen.  Some  of  the 
metals  also,  combined  with  a small  proportion  of  oxygen,  give  ox- 
ides capable  of  uniting  with  acids  and  of  composing  salts , and  again 
united  with  more  oxygen  yield  an  acid  which  is  susceptible,  with 
oxides,  of  forming  saline  compounds. 

Action  of  374.  When  acids,  containing  much  oxygen,  are  poured  on  sub- 
faining°ox-  stances  that  have  a great  affinity  for  this  element,  as  metals  and 
ygen.  some  inflammable  bodies,  oxygen  is  rapidly  taken  from  them.  The 
combination  with  the  liberated  oxygen  is,  in  some  cases,  so  rapid, 
as  to  give  rise  to  combustion  ; as  when  nitric  acid  is  poured  upon 
spirits  of  turpentine,  or  phosphorus.  See  nitric  acid. 

Oxidation''  375.  Mercury  is  speedily  oxidized  by  the  same  acid,  and  also  if 
of  mercury.  b0i}e(i  in  sulphuric  acid.  In  both  cases,  however,  the  oxide  formed 
by  the  decomposition  of  one  portion  of  the  acid  unites  with  another 
portion  that  has  not  been  decomposed,  and  the  resulting  products  are 
a nitrate  and  a sulphate  of  the  oxide  of  mercury. 

Deoiida-  376.  When  oxygen  is  to  be  removed  from  any  substance  which 
tion.  does  not  part  with  it  on  exposure  to  heat,  the  substance  is  often 
mixed  with  charcoal,  which,  at  a high  temperature,  has  a much 
greater  affinity  for  oxygen  than  most  other  substances.  It  is  in  this 
manner  that  most  of  the  common  metallic  oxides  are  deoxidized,  and 
their  bases  procured  in  a metallic  form  ; the  carbon  combining  with 
the  oxygen  and  passing  off  in  the  form  of  carbonic  acid  gas.  F. 


Section  II.  Hydrogen. 

Symb.  Sp.  Gr.  Chem.  Equiv. 

H.  0.0689  air  =1  By  Vol.  100 

1. 00  Hyd.=l  “ Wgt.  1 

Discovery , 377  This  gas  was  formerly  termed  inflammable  air , from 

its  combustibility,  and  phlogiston , from  the  supposition  that  it 
was  the  matter  of  heat ; but  the  name  hydrogen , from  vSmq  water, 
and  yevvetv  to  generate,  has  now  become  general.  Its  nature  and 
leading  properties  were  first  pointed  out  in  the  year  1766  by  C-aven- 
dish.t 

The  most  simple  form  in  which  it  has  hitherto  been  obtained,  is 
in  that  of  a gas.  Of  its  nature  we  know  but  little,  but  as  it  has  not  yet 


* S«e  Dalton’s  Chem.  Philos.  11.  309. 


t Phil.  Trans,  lvi.  144. 


Methods  of  Procuring. 


123 


been  resolved  into  any  more  simple  form,  it  is  still  arranged  among  Sect.n. 
elementary  bodies, 

378.  To  procure  hydrogen  gas,  let  sulphuric  acid,  previously  di-  Method  of 
luted  with  five  or  six  times  its  weight  of  water,  be  poured  on  iron  JJ^Jogen 
filings,  or  on  small  iron  nails  ; or  (what  is  still  better)  pour  sulphuric  gas. 
acid  diluted  with  eight  parts  of  water,  on  zinc,  granulated  by  pour- 
ing it  melted  into  cold  water,  and  contained  in  a gas  bottle,  Figs.  86, 

87,  or  small  retort.  An  effervescence  will  ensue,  and  the  escaping  gas 
may  be  collected  in  the  usual  manner  over  water. 

379.  An  ingenious  apparatus  for  obtaining  it  instantaneously  in  a Inflamma- 
laboratory,  was  contrived  by  Gay-Lussac. 


ble  air 
lamp. 


It  consists  of  a three  necked  glass  bottle,  (Fig.  119,)  one  of 
whose  openings  has  a stopper,  from  which  is  suspended  a 
small  cylinder  of  zinc  a.  To  the  opposite  aperture  is  fixed 
a bent  brass  tube  furnished  with  a stop-cock,  on  which  may 
be  screwed  either  a small  jet  for  burning  the  gas,  or  a tube  to 
conduct  it  wherever  it  may  be  required.  The  upper  vessel  is 
of  glass,  and  ground  to  fit  the  middle  neck,  its  pipe  reaching 
within  a small  distance  of  the  bottom  of  the  bottle.  To  use 
the  apparatus,  the  lower  vessel  is  filled  with  sulphuric  acid 
properly  diluted,  aud  the  zinc  cylinder  is  then  introduced,  the 
stopper  being  closed  to  which  it  is  affixed,  and  the  cover  of 
the  upper  vessel  removed.  The  gas  which  is  generated  drives 
the  diluted  acid  into  the  upper  vessel,  and  the  further  produc- 
tion of  it  ceases,  when  the  zinc  is  completely  uncovered.  We 
have  then  the  bottle  filled  with  gas ; and  can  at  any  time  expel  it  by  opening 
the  cock,  and  allowing  the  atmosphere  to  press  on  the  surface  of  the  liquid  in 
the  globular  vessel. 

A more  convenient  modification  of  this  apparatus  has  been  contrived  by  Hare  Self-remi- 
(Fig.  120.)  It  consists  of  two  vessels,  one  withinthe  Fig.  120 

other,  the  inner  one  having  no  bottom  is  furnished 
with  a stop-cock  at  the  upper  part,  A piece  of  zinc  is 
suspended  in  the  inner  vessel;  acid  and  water,  previ- 
ously cooled,  being  poured  into  the  space  between 
the  two  vessels,  (the  stop-cock  being  open,)  will  expel 
the  air  and  rise  in  the  inner  vessel ; coming  in  com 
tact  with  the  zinc,  hydrogen  will  be  given  off.  The 
gas  should  be  allowed  to  escape  until  all  the  air  has 
been  expelled  from  the  inner  vessel.  The  stop-cock 
being  now  closed,  the  hydrogen  will  accumulate  in 
the  inner  vessel,  press  upon  the  acid  and  water,  and 
force  it  into  the  space  between  the  two  vessels. 

This  will  go  on  until  the  zinc  is  no  longer  in  contact 
with  the  liquid.  The  inner  vessel  will  be  a reservoir 
of  hydrogen,  from  which  any  desired  quantity  can 
be  drawn  on  opening  the  stop-cock.  A straight  pipe,  or  flexible  tube,  being 
screwed  upon  the  stop-cock,  the  gas  may  be  conveyed  into  any  other 
piece  of  apparatus.  As  the  gas  passes  out,  the  acid  and  water  rise  in  the 
inner  vessel,  and  again  come  in  contact  with  the  zinc,  and  more  hydrogen  is 
obtained. 

380.  Hydrogen  gas,  thus  obtained,  is  not,  however,  to  be  consi-  Impure  as 

dered  as  absolutely  pure.^  commonly 

J 1 obtained. 

* The  gas  may  be  partially  purified  by  passing  it  through  a solution  of  pure  potassa, 
or  obtained  purer  by  using  distilled  zinc.  In  order  to  purify  the  zinc.  Thomson  ex- 
poses it  to  a white  heat  in  a stone  ware  retort,  luted  to  a receiver  nearly  filled  with 
water.  At  this  temperature,  the  zinc  is  sublimed  and  freed  from  all  its  impurities, 
except  a trace  of  cadmium  too  minute  to  occasion  any  sensible  error.  The  zinc  thus 
distilled  over  is  melted  in  a crucible  and  poured  upon  the  surface  of  a clean  smooth 
sandstone,  upon  which  it  forms  a thin  sheet  which  can  be  easily  broken  into  small 
pieces.  T.  First  Prin.  1.  52. 


124 


Hydrogen. 


Chap,  in.  381.  Hydrogen  is  an  aeriform  fluid,  but  very  slightly  absorbable 
Properties,  by  water.  It  has  no  taste,  and  may  be  respired  for  a short  time, 
though  it  is  fatal  to  small  animals.  As  usually  prepared,  it  has  a 
disagreeable  odour,  but  when  pure  has  none.# 


It  may  be  breathed  a few  times  with  safety,  and  if  the  experimenter  speak 
immtdiutely  on  removing  his  lips  from  the  mouth-piece  of  the  bag  or  bladder,  a 
remarkable  change  in  the  voice  is  perceived. 


Weight  and 

specific 

gravity. 


382.  It  is  the  lightest  body  known,  and  is  therefore  conveniently 
assumed  as  unity  in  speaking  of  the  specific  gravity  of  gases,  as  well 
as  in  referring  to  the  proportions  in  which  bodies  combine.  100  cu- 
bic inches  weigh  2.1367  grains.  It  is  16  times  lighter  than  oxygen. 

383.  The  levity  of  hydrogen  may  be  proved  by  experiment. 


Exp.  Let  a jar  filled  with  this  ga6  stand,  for  a few  seconds,  with  its  open  mouth  up- 

wards. On  letting  down  a candle,  the  gas  will  be  found  to  have  escaped. 

EXp  Place  another  jar  of  the  gas  inverted,  or  with  its  mouth  downwards.  The  gas 

will  now  be  found  to  remain  a short  time  in  the  jar,  being  prevented  from  escap- 
ing upwards  by  the  bottom  and  sides  of  the  vessel. 


Exp. 


Exp. 


Inflamma- 

ble. 


354.  Hydrogen,  in  consequence 
ployed  for  filling  air-balloons. 

Fill  with  hydrogen  gas,  a bladder  fur- 
nished with  a stop-cock,  (Fig  J21 ;)  and 
adapt  to  this  a common  tobacco  pipe.  Dip 
the  bowl  of  the  pipe  into  a lather  of  soap, 
and,  turning  the  cock,  blow  up  the  lather 
into  bubbles  ; instead  of  falling  to  the 
ground  like  those  commonly  blown  by 
children,  they  will  rise  rapidly  into  the 
air. 

The  experiment  may  be  varied  by  filling  the  bladder  with  a mixture  of  two 
parts  of  hydrogen  gas  and  one  of  oxygen  gas.  Bubbles,  blown  with  this  mixture, 
take  firo  on  the  approach  of  a lighted  candle,  and  detonate  with  a loud  report. 
It  is  proper,  however,  not  to  6et  them  on  fire  till  they  are  completely  detached 
from  the  bowd  of  the  pipe. 

355.  Hydrogen  is  inflammable,  and  when  pure  burns  with  a lam- 
bent blue  flame  at  the  surface  in  contact  with  the  air. 


of  its  extreme  lightness,  is  em- 


Fig.  121. 


Exp. 

Exp. 


Exp. 


Exp. 


Fill  a small  jar  with  the  gas,  and,  holding  it  with  the  mouth  downwards,  bring 
the  gas  into  contact  with  the  flame  of  a candle. 

Fill  with  this  gas  a bladder  which  is  furnished  with  a stop-cock,  and  with  a 
small  pipe,  of  diameter  less  than  that  of  a common  tobacco  pipe.  Press  the  air 
out  through  the  pipe,  and  on  presenting  a lighted  candle,  the  stream  will  take  fire, 
and  continue  to  burn  with  a pale  and  leeble  flame. 


3S6.  Hydrogen  gas  does  not  support  combustion. 

Remove  ajar,  filled  with  the  gas,  from  the  shelf  of  the  pneumatic 
trough,  upon  a plate  ; bring  it  near  a lighted  candle,  and  expedi- 
tiously removing  the  plate,  cover  the  candle  ; it  will  be  extinguished. 
At  first  there  will  be  a slight  explosion,  from  the  gas  at  the  mouth 
of  the  jar  mixing  with  atmospheric  air. 

Suspend  a long  tube  or  jar  (Fig.  122),  with  its  mouth  downward, 
containing  hydrogen  gas ; remove  the  stopple  and  introduce  a light- 
ed taper  attached  to  a long  wire.  The  flame  of  the  taper  may  be 
extinguished  and  relighted  many  times,  as  the  taper  is  passed  up 
into  the  eas,  or  brought  down  slowly  through  the  portion  burning  at 
the  mouth  of  the  jar  Care  should  obviously  be  taken,  that  w ater 
does  not  remain  about  the  mouth  of  the  jar. 


* Herzelius  has  shown  that  the  gas  generated  from  iron  filings  and  di- 
lute sulphuric  acid,  loses  its  odour  by  being  passed  through  pure  alcohol, 
and  when  the  alcohol  is  diluted  with  water  and  is  kept  a few  days,  an 
odorous  volatile  oil  is  separated,  which  caused  the  smell  of  the  gas. 


Fig.  122. 


Detonation  with  Oxygen.  125 

Persons  who  are  provided  with  the  jars  represented  Fig.  94,  a , may  screw  to  sec.  II. 
the  cook  a brass  pipe  with  a small  aperture.  On  pressing  the  jar,  filled  with  hy-  ~ ~ 

drogen  gas,  into  the  water,  and  opening  the  cock,  the  gas  will  be  forced  out  in  a^xP? 
stream,  which  may  be  set  on  fire.  On  this  principle  are  founded  the  artificial 
fireworks  without  smell  or  smoke.  They  consist  of  pipes,  having  variously 
sized  apertures,  some  of  which  have  a rotary  motion. 

Or  the  gas  may  be  condensed,  by  means  of  a syringe,  into  a strong  copper  globe 
furnished  with  a stop-cock,  to  which,  on  removing  the  syringe,  a brass  tube  can 
be  screwed,  and  a variety  of  jets  and  revolving  burners  be  attached. 

387.  It  has  been  found  by  Doebereiner,  that  when  a stream  of  hy- Doeberein- 
drogen  is  directed  upon  spongy  platinum,  the  platinum  soon  becomes  er’s 

red  hot,  and  the  hydrogen  is  inflamed.^  gen  a 

This  discovery  has  led  to  various  modifications  of  the  in- 
flammable air  lamp.  A very  convenient  and  ornamen- 
tal form  of  which  is  represented  in  Fig.  123.  It  is  com- 
posed of  two  glass  vessels  fitted  to  each  other  by  grinding,  as 
m the  apparatus  of  Gay  Lussac.  The  tube  a,  of  the  upper 
vessel,  is  encompassed  by  a cylinder  of  zipc,  which  is  sup- 
ported by  a ring  of  cork  on  the  lower  part  of  the  tube-  The 
platinum  sponge  is  contained  in  a small  brass  box  A,  attached 
to  a brass  wire  passing  through  a collar  of  leather  and  which 
can  be  placed  at  any  distance  from  the  jet  c When  a light 
is  required  the  cock  d is  turned,  and  the  pressure  of  the  acid 
liquor  in  the  upper  vessel  expels  the  hydrogen,  as  in  the  ap- 
paratus already  described.! 

388.  If  mixed  with  common  air,  hydrogen  burns  rapidly  with  de- Detonates 

tonation.  with  air. 


Fig  123. 


Into  a strong  phial,  capable  of  holding  about  6 ounces  of  water  introduce  one 
part  of  hydrogen  and  three  parts  of  common  air.  On  applying  a lighted  candle 
or  a red  hot  wire,  the  mixture  will  explode. 

This  experiment  may  be  performed  by  means  of  an  apparatus  called  the  in-  Inflamma- 
flammable  air  pistol.  (Fig.  124.)  This  instrument  consists  of  pjg.  124.  ble  air  pis- 
a cylinder  of  brass,  about  three  fourths  of  an  inch  in  diameter,  CL  ^ tol. 

and  six  inches  long,  in  the  form  of  a small  cannon  or  pistol- 
barrel,  properly  mounted,  and  having  a wire  a,  passing 
through  a tube  of  ivory,  6,  and  not  quite  touching  the  interior 
of  the  cylinder,  at  the  part  usually  occupied  by  the  touch- 
hole;  an  electric  spark  communicated  to  this  wire  inflames  the  mixture  of  hydro- 
gen and  atmospheric  air  in  its  interior.  It  may  be  charged,  by  holding  it  for  a 
moment  over  the  open  jet  of  the  instrument  (Fig.  119),  always  taking  care  that 
there  is  a due  admixture  of  atmospheric  air,  otherwise  the  electric  spark  will  not 
inflame  it. 

389.  If  the  experiment  be  repeated  with  oxygen  gas  instead  of  Detonates 
atmospherical  air;  changing  the  proportions,  and  mixing  only  one  with  oxy- 
part  of  the  oxygen  gas  with  two  of  hydrogen,  the  report  will  be  con-  gen» 
siderably  louder.  The  bottle  should  be  a strong  one,  and  should  be 
wrapped  round  with  cloth,  to  prevent  accident. 

It  may  be  exploded  by  igniting  a fine  platinum 
wire  within  a strong  glass  vessel  (Fig.  125,  b ); 
the  wire  may  be  an  inch  in  length,  and  connected 
with  two  stout  copper  wires  a a passing  in  at  the 
sides  through  a cork  : the  copper  wires  should 
be  attached  to  the  vices  of  a small  calorimotor  c. 

The  acid  liquor  being  contained  in  a glass  or 
other  suitable  vessel  d,  is  to  be  raised  up  suffi- 
ciently to  have  the  plates  immersed.  See  Gal- 
vanism. 


* A convenient  tinder  may  be  prepared  from  a 
piece  of  cotton  cloth,  dipped  in  the  solution  from 
which  the  sponge  is  obtained,  (see  Platinum ,)  and  then  inflamed  ; it  ignites  as  rea- 
dily as  the  platinum  sponge  ; the  sponge  and  tinder  should  be  perfectly  dry.  W. 
t See  the  subject  of  Eudiometry. 


Fig.  125. 


126 


Chap.  III. 
Exp. 


And  by 
means  of 
the  electric 
spark. 


Explosion 
by  electrici- 
ty, flame, 
&c. 


Hydrogen, 


A bladder,  filled  with  hydrogen  and  oxygen,  may  be  exploded  with  safety 
by  suspending  it  from  the  ceiling,  and  piercing  it  with  a sharp  wire  at  the 
end  of  a long  stick,  with  a little  tow  about  it,  dipped  in  spirits  of  turpentine  and 
burning. 

390.  The  same  experiment  may  be  made  over  water,  by  means  of 
the  electric  spark. 


Procure  a strong  tube,  about  three  quarters  of  an  inch  in  diame- 
ter, and  12  inches  long,  closed  at  one  end.  (Fig.  126  ) About  a 
quarter  or  half  an  inch  from  the  sealed  end,  let  two  small  holes 
be  drilled,  opposite  to  each  other,  ,and  into  each  of  these  let  a 
brass  conductor  be  cemented,  so  that  the  two  points  may  be  dis- 
tant from  each  other,  within  the  tube,  about  one  eighth  of  an 
inch.  An  apparatus,  serving  the  same  purpose,  and  much  more 
easily  constructed,  may  be  formed  by  hermetically  sealing  a piece 
of  brass  wire,  or  still  better,  platinum  wire,  into  the  end  of  a glass 
tube.  With  this  conductor,  an  interrupted  circuit  may  be  formed 
by  introducing  into  the  tube  a longer  wire,  one  end  of  which  ter- 
minates one  tenth  of  an  inch  from  the  upper  one,  while  the  other 
extends  beyond  the  aperture  of  the  tube.  (See  Fig.  127,  c.)  Into 


Fig.  126. 


this  tube,  standing  over  water,  pass  about  half  a 
mixture  of  hydrogen  and  oxygen  gases  ; in  the 
proportion  of  two  measures  of  the  former  to  one 
of  the  latter.  Hold  the  tube  firmly,  and  pass  an 
electric  spark  through  the  mixed  gases.  For  re- 
lieving the  shock,  which  is  sometimes  considera- 
ble on  firing,  an  ingenious  contrivance  of  Davy 
may  be  employed.*  The  first  effect  of  the  com- 
bustion is  a sudden  and  considerable  enlargement 
of  volume,  which,  from  some  experiments  of  Davy 
probably  amounts  to  15  times  the  original  bulk 
of  the  mixture.  After  this  the  gases,  if  per- 
fectly pure  and  in  the  proper  proportion,  will 
be  found  to  have  disappeared  entirely.  H.  1.  235. 


cubic  inch  of  a 


391.  The  power  of  flame  and  electricity,  in  causing  a mixture  of 
hydrogen  with  air  or  oxygen  gas  to  explode,  is  limited;  flame  occa- 
sions a very  feeble  explosion  when  the  hydrogen  is  mixed  with  nine 
times  its  bulk  of  air;  and  a mixture  of  four  measures  of  hydrogen 
with  one  of  air  does  not  explode  at  all.  An  explosive  mixture,  form- 
ed of  two  measures  of  hydrogen  and  one  of  oxygen  gas,  explodes 
from  all  the  causes  above  enumerated.  Biot  found  that  sudden  and 
violent  compression  likewise  causes  an  explosion,  apparently  from 
the  heat  emitted  during  the  operation  ; for  an  equal  degree  of  con- 
densation, slowly  produced,  has  not  the  same  effect.  The  electric 
spark  ceases  to  cause  detonation,  when  the  explosive  mixture  is  di- 
luted with  twelve  times  its  volume  of  air,  fourteen  of  oxygen,  or  nine 
of  hydrogen  ; or  when  it  is  expanded  to  sixteen  times  its  bulk  by  di- 
minished pressure.  Spongy  platinum  acts  just  as  rapidly  as  flame 
or  the  electric  spark  in  producing  explosion,  provided  the  gases  are 
quite  pure  and  mixed  in  the  exact  ratio  of  two  to  one.t  Fara- 
day finds  that  platinum  foil,  if  perfectly  clean,  produces  gradual 
though  rather  rapid  combination  of  the  gases,  often  followed  by  ex- 
plosion.! 


* Phil.  Mag.  xxxi.  3. 

t For  a variety  of  facts  respecting  the  causes  which  prevent  the  action  of  flame,  elec- 
tricity, and  plaiinum  in  producing  detonation,  the  reader  may  consult  the  essay  of 
Grotthus  in  the  Ann.  de  Chimie  vol.  lxxxii. ; Davy’s  work  on  Flame ; Henry’s  essay 
in  the  Phil.  Trans,  for  1824;  and  a paper  by  Turner  in  the  Edin.  Philos.  Jour,  for 
the  same  year. 
t Phil.  Trans.  1834. 


127 


Hare’s  Compound  Blow-pipe. 


392.  When  the  action  of  heat,  the  electric  spark,  and  spongy  plati-  sect,  ii. 
nurn  no  longer  causes  explosion,  a silent  and  gradual  combination  be-siow  com- 
tween  the  gases  may  still  be  occasioned  by  them.  Davy  observed  that  bination, 
oxygen  and  hydrogen  gases  unite  slowly  with  one  another,  when 

they  are  exposed  to  a temperature  above  the  boiling  point  of  mercury, 
and  below  that  at  which  glass  begins  to  appear  luminous  in  the  dark. 

An  explosive  mixture,  diluted  with  air  to  too  great  a degree  to  ex- 
plode by  electricity,  is  made  to  unite  silently  by  a succession  of 
electric  sparks.  Spongy  platinum  causes  them  to  unite  slowly 
though  mixed  with  one  hundred  times  their  bulk  of  oxygen  gas.  T.160. 

393.  A current  of  hydrogen  may  be  inflamed  when  issuing  from  a Musical 
small  aperture,  and  if  a tube  of  eighteen  or  twenty  inches  in  length 

be  held  over  the  flame,  a peculiar  musical  tone  is  produced.  This  combustion 
effect  is  not  peculiar  to  hydrogen,  but  is  produced  by  a variety  of  of  hydro- 
other  flames,  and  is  referable  to  the  succession  of  explosions  pro- gen' 
duced  by  the  combustion  of  the  gas  in  the  tube. 

394.  The  tendency  which  gaseous  fluids  have  to  become  com-  Gases  have 
pletely  mixed  under  all  circumstances,  and  as  it  were  to  penetrate  tendency  to 
each  other,  is  well  illustrated  where  hydrogen  is  employed.  Thus,  mix  to- 

if  two  small  phials,  the  one  containing  oxygen  and  the  other  hydro-  Selher- 
gen,  be  connected  perpendicularly  by  a long  glass  tube,  of  small  bore, 
it  will  be  found,  that  although  the  hydrogen  be  uppermost,  and  much 
lighter  than  the  oxygen*  it  will,  in  the  course  of  a few  hours,  have 
perfectly  mixed  with  the  oxygen,  and  the  gases  will  be  found  in 
equal  proportions  in  both  phials.  Dalton  has  shown  that  gases,  un- 
like other  fluids,  do  not  remain  upon  each  other  without  admixture.^ 

395.  The  flame  of  hydrogen  is  occasionally  employed  for  exciting  Hare’s 
intense  heat ; and  it  has  been  found  when  mixed  with  oxygen  and  blow-pipe, 
burned  as  the  mixture  issues  from  a small  jet,  to  excite  a tempera- 
ture nearly  equal  to  that  of  the  arc  of  flame  in  the  Voltaic  circuit. 

A blow-pipe  upon  this  construction  was  first  made  by  Hare : 

It  consists  of  a cylindrical  vessel  of  tin,  (Fig.  128,  a ,) 
or  what  is  preferable  copper,  divided  in  the  middle  by 
two  partitions,  so  as  to  form  two  distinct  reservoirs,  one 
for  oxygen  and  the  other  for  hydrogen.  Into  the  lower 
part  of  each  reservoir,  a tube  b,  is  inserted  somewhat 
obliquely,  as  in  the  common  gas-holder.  Above  the 
reservoirs  is  a conical  tin  funnel  c,  furnished  with  a stop- 
cock and  connected  with  a tube  which  immediately  be- 
low divides  into  two,  one  passing  to  each  reservoir.  A 
tube  passes  out  from  each  reservoir,  meeting  in  a 
cone  d (a  section  of  which  is  represented  at  e).  The 
gases  are  thus  mingled  and  are  then  made  to  issue 
through  a capillary  tube  drilled  through  a wire  of  silver 
and  inserted  into  the  cone. t The  lower  tubes  being  closed, 
the  apparatus  is  filled  with  water,  and  the  gases  introduc- 
ed, as  in  the  usual  method  of  filling  a gas-holder.  The  re- 


Fig.  128. 


* Manchester  Memoirs,  vol.  i.  New  Series. 

t The  arrangement,  consisting  of  two  separate  reservoirs  for  the  gases,  is  perfectly  safe 
and  convenient : the  jet  may  be  formed  of  two  concentric  cones.  In  1824  I devised  a jet, 
which  was  made  for  me  by  Newman  of  London,  to  whom  I sent  a drawing  and  de- 
scription. It  is  the  only  jet  I have  been  in  the  habit  of  using  since  that  time,  and  it 


has  proved,  as  anticipated,  perfectly  safe.  It  consists 
of  two  concentric  tubes  of  brass  (Fig.  129),  each  ter- 
minated by  platinum,  a space  being  left  between  the 
two.  By  one  stop-cock,  opening  into  the  space,  and 
another  into  the  cavity  of  the  inner  tube,  the  two  gases 


RwJLj^I 


Fig.  129. 


128 


Chap.  III. 


Brooke’s 

blow-pipe. 


Hemming’! 
safety  tube, 


Burns  un- 
der water. 


Hydrogen *  * 

servoirs  being  filled,  the  lower  tubes  are  closed,  and  water  poured  into  the  funnel 
'on  opening  the  stop-cocks  the  gases  are  propelled  through  the  jet.  When  sub- 
stances are  to  be  exposed  to  the  action  of  this  instrument,  the  stop-cock  connect- 
ed with  the  reservoir  of  hydrogen  should  be  first  opened  and  the  gas  may  be 
inflamed ; the  other  stop-cock  is  then  gradually  opened,  and  the  oxygen  mixing 
with  the  hydrogen,  an  intensely  high  temperature  is  obtained. 

With  this  instrument  Hare  and  Silliman  first  effected  the  fusion  of 
some  of  the  most  refractory  substances  in  nature.* 

396.  The  blow-pipe  invented  by  Brooke  depends  for  its  action  on 
the  elasticity  of  compressed  air,  and  consists  of  a strong  copper  box 
(Fig.  130),  into  which  several  atmospheres 
are  crowded  by  means  of  a condensing  sy- 
ringe. Various  expedients  have  been 
adopted  to  render  this  a safe  substitute  for 
the  oxy-hydrogen  blow-pipe  of  Hare.  It 
may  be  done  by  interposing  between  the 
flame  and  the  main  reservoir  of  gases,  a 
cylinder  containing  a little  water  or  oil, 
through  which  by  means  of  a valve  at  the 
bottom,  the  gases  are  allowed  to  pass. 

The  safety  of  the  instrument  is  increased 
by  the  safety  tube,  lately  proposed  by  Hem- 
ming. 

It  consists  of  a brass  cylinder,  about  six  inches 
long,  and  three  fourths  of  an  inch  wide,  filled 
with  very  fine  brass  wire,  in  length  equal  to  that 
of  the  tube.  A pointed  rod  of  metal,  one  eighth 
of  an  inch  thick,  is  then  forcibly  inserted  through 
the  centre  of  the  bundle  of  wires  in  the  tube,  so  as 
to  wedge  them  tightly  together.  The  interstices 
between  the  wires  thus  constitute  very  fine  metallic  tubes,  the  conducting  power 
of  which  is  so  great  as  entirely  to  intercept  the  passage  of  flamed  J 

397.  The  flame  produced  by  the  oxy-hydrogen  blow-pipe  continues 
to  burn  when  submersed  in,  and  in  actual  contact  with,  water,  with 
the  same  splendour  as  in  the  atmosphere  ; the  only  difference  being 
that  under  water  its  figure  is  conglobated,  whereas  in  air  it  assumes 
that  of  a long,  slender,  conical  pencil.  Care  is  required  to  introduce 
the  flame  slowly  into  the  water.  A piece  of  pine  wood  or  cork  when 
brought  within  the  action  of  the  submerged  flame  gives  out  a bril- 
liant light. 

are  conveyed  along  the  jet  without  mingling  until  they  arrive  at  the  orifice  where  they 
are  burned.  Either  gas  may  he  made  to  surround  the  other  at  pleasure  merely  by 
changing  the  connexion  with’the  reservoirs  In  the  Phil.  Mag.  ii.  third  series,  Daniell 
has  described  a similar  jet.  I was  not  aware  until  these  pages  were  passing  through 
the  press  that  a jet  of  similar  construction  had  been  early  employed  by  Hare.  W. 

* Amer.  Jour,  of  Sci.  vol.  ii.  p.  281,  &c.  t Phil.  Mag.  third  series,  i.  82. 

t In  some  recent  experiments  with  mixtures  of  the  gases,  contained  in  bladders  at- 
tached to  the  extremities  of  this  tube.  I have  found  it  impossible  to  explode  both  by 
firing  one,  and.  have  been  led  to  attach  it  to  a large  globe  of  copper  in  which  the  gases 
are  condensed,  and  with  a simple  jet  at  the  other  extremity,  use  the  apparatus  with 
perfect  safety.  W. 


Fig.  130. 


129 


Water -—Theory. 

Hydrogen  and  Oxygen.  Protoxide  of  Hydrogen — Water.  Sect.  11. 

Composition* 

Symb.  H+O  or  H,  By  Wght . By  Vol. 

sometimes  acj.  Hyd.  Oxy-  Equiv.  Hyd.  Oxy. 

from  aqua.  1 or  1 eq.  -f-  8 or  1 eq.  =9  100  50 

398.  Hydrogen  and  Oxygen , Water. — When  two  volumes  of  hy- 
drogen gas  are  mixed  with  one  volume  of  oxygen  gas,  and  the  mix-  Union  with 
ture  inflamed  in  a proper  apparatus  by  the  electric  spark,  the  gases  oxygen  gas, 
totally  disappear,  and  the  interior  of  the  vessel  is  covered  with  drops  water*CeS 
of  pure  water,  equal  in  weight  to  that  of  the  gases  consumed. 

399*  If  pure  water  be  exposed  to  the  action  of  Voltaic  electricity, 

it  is  resolved  into  two  volumes  of  hydrogen,  and  one  volume  of  oxy-  Decomposi- 

gen,  so  that  water  is  thus  proved  by  synthesis  and  analysis,  to  con- tion  of  wa- 

sist  of  two  volumes  of  hydrogen  combined  with  one  volume  of  by elec- 
J ° tricity, 

oxygen. 

400.  Cavendish  demonstrated  the  composition  of  water  by  burning 
oxygen  and  hydrogen  gases  in  a dry  glass  vessel ; when  a quantity  B com_ 
of  pure  water  was  generated,  exactly  equal  in  weight  to  that  of  the  bustion. 
gases  which  had  disappeared.  This  experiment,  which  is  the  syn- 
thetic proof  of  the  composition  of  water,  was  afterwards  made  on  a 
much  larger  scale  in  Paris  by  Vauquelin,  Fourcroy,  and  Seguin. 

Lavoisier  first  demonstrated  its  nature  analytically. 

The  composition  of  water  by  weight  was  determined  with  great 
care  by  Berzelius  and  Dulong ; and  their  result  is  regarded  as  a 
nearer  approximation  to  the  truth  than  that  of  any  of  their  predeces-  tiorTIJy*1" 
sors.  They  state,  as  a mean  of  three  careful  experiments,^  that  weight. 
100  parts  of  pure  water  consist  of  11.1  of  hydrogen  and  S8.9  oxy- 
gen, which  is  the  ratio  of  1 to  8.009,  very  nearly  that  of  1 to  8 above 
stated. 

40 1.  The  processes  for  procuring  hydrogen  gas  will  now  be  intelli- 
gible. The  first  is  the  method  by  which  Lavoisier  made  the  analysis 

of  water.  It  is  founded  on  the  fact,  that  iron  at  a red  heat  decomposes  fofmaUorf 
water,  the  oxygen  of  that  liquid  uniting  with  the  metal,  and  the  hy-  of  hydro- 
drogen  gas  being  set  free.  The  hydrogen  which  is  evolved  when  £en- 
zinc  or  iron  is  put  into  dilute  sulphuric  acid  must  be  derived,  from 
the  same  source.  The  product  of  the  operation,  besides  hydrogen, 
is  sulphate  of  the  protoxide  of  iron,  if  iron  is  used,  or  of  the  oxide  of 
zinc,  when  zinc  is  employed.  The  knowledge  of  the  combining  pro-’ 
portions  of  these  substances  will  give  the  exact  quantity  of  each  pro- 


duct. These  numbers  are— 

Water  (8  oxy  q_  1 hyd.  .....  9 

Sulphuric  acid  ......  40.1 

Iron  28 

Protoxide  of  iron  (28  iron  + 8 oxygen)  . 36 

Sulphate  of  the  protoxide  of  iron  (40.1+36)  . 76.1 


Hence  for  every  9 grains  of  water  which  are  decomposed,  1 grain  of 
hydrogen  will  be  set  free  ; 8 grains  of  oxygen  will  unite  with  28 
grains  of  iron,  forming  36  of  the  protoxide  of  iron  ; and  the  36  grains 
of  protoxide  will  combine  with  40.1  grains  of  sulphuric  acid,  yielding 
76.1  of  sulphate  of  the  protoxide  of  iron.  A similar  calculation  may 
be  employed  when  zinc  is  used,  merely  by  substituting  the  equiva- 


* Ann.  de  Chim.  et  de  Phys.  vol.  xv . 


17 


130 


Hydrogen  and  Oxygen. 


Chap.  III. 


Action  of 
zinc,  &c. 


Exp. 


Burns  with 
OX^  KD  gas 
and  forms 
water, 


The  mix* 
ture  ex- 
plodes. 
Exp. 


Exp. 


Water  a 
compound 
of  the  bases 
of  the 
gases. 


lent  of  zinc  (32.3)  for  that  of  iron.  According  to  Cavendish,  an 
ounce  of  zinc  yields  676  cubic  inches,  and  an  equal  quantity  of  iron 
782  cubic  inches  of  hydrogen  gas. 

402.  The  action  of  dilute  sulphuric  acid  on  metallic  zinc  affords  an 
instance  of  what  was  once  called  Disposing  Affinity.  Zinc  decom- 
poses pure  water  at  common  temperatures  with  extreme  slowness ; 
but  as  soon  as  sulphuric  acid  is  added,  decomposition  of  the  water 
takes  place  rapidly,  though  the  acid  merely  unites  with  oxide  of  zinc. 
The  former  explanation  was,  that  the  affinity  of  the  acid  for  oxide  of 
zinc  disposed  the  metal  to  unite  with  oxygen,  and  thus  enabled  it  to 
decompose  water;  that  is,  the  oxide  of  zinc  was  supposed  to  produce 
an  effect  previous  to  its  existence.  The  obscurity  of  this  explanation 
arises  from  regarding  changes  as  consecutive,  which  are  in  reality 
simultaneous.  There  is,  as  it  were,  but  one  chemical  change,  which 
consists  in  the  combination  at  one  and  the  same  moment  of  zinc  with 


oxygen,  and  of  oxide  of  zinc  with  the  acid  : and  this  change  occurs  be- 
cause these  two  affinities,  acting  together,  overcome  the  attraction  of 
oxygen  and  hydrogen  for  one  another.  T. 

403.  The  experiments  illustrating  the  composition  of  water  may 
be  divided  into  synthetic  and  analytic.  Among  these  the  following 
may  be  selected. 


Fig.  131.  Burn  a current  of  hydrogen  under 

the  funnel  a,  (Fig  131),  by  uniting 
with  the  oxygen  of  the  atmosphere  it 
will  produce  aqueous  vapour,  which 
passing  into  the  glass  cylinder  i,  will 
condense  in  drops. 

Fig.  132  represents  an  apparatus  for 
showing  the  production  of  water  by 
burning  a current  of  hydrogen  in  an  at- 
mosphere of  oxygen,  a is  a glass  cyl- 
inder, which, after  having  been  exhaust- 
ed upon  an  air-pump,  is  filled  with  pure  oxygen,  b is  a receiver  of 
hydrogen  immersed  in  the  vessel  of  water  c,  by  which  the  gas  is 
compressed,  so  as  to  be  urged  through  the  capillary  opening/,  when 
the  stop-cocks  d d are  open,  e is  a platinum  wire  by  which  the  gas 
may  be  infiamed  by  an  electric  spark.  It  burns  with  the  production 
of  Intense  lieat,  and  water  is  soon  collected  in  drops  upon  the  inte- 
rior of  the  cylinder. 

Jf. two  measures  of  pure  hydrogen  be  mixed  with  one  of  pure  oxy- 
gon, and  detonated  in  the  graduated  glass  tube  a,  (Fig.  lOti),  stand- 
ing over  water,  by  an  electric  spark  passed  through  the  Dlatinum  wires 
Fig.  133.  ft  ft,  the  gases  will  entirely  disappear.  It  there  be  any 

vill 


Cl 


excess  of  either  of  the  gases,  the  portion  in  excess  w 
remain  unconsumed. 

The  same  experiment  may  be  thus  varied  : Fig.  133  

is  a very  strong  glass  vessel,  capable  of  holding  about  half  a pint 
and  furnished  (besides  the  proper  contrivance  at  top  for  taking  the 
electric  spark  in  it)  with  a brass  cap  and  cock,  by  means  of  which  it 
can  be  screwed  to  the  transfer  plate  of  an  air  pump.  When  exhaust- 
ed, it  may  be  filled  with  a mixture  of  oxygen  and  hydrogen  gases, 
in  the  proportion  of  one  measure  of  the  former  to  two  of  the  latter, 
and  an  electric  spark  maybe  passed  through  the  mixture.  After  the 
explosion,  when  time  has  been  given  to  the  vessel  to  cool,  a sensible 
quantity  of  moisture  will  have  condensed  on  the  inner  surface  of 
the  vessel,  and  by  repeating  the  operation  frequently,  a sufficient 
quantity  of  fluid  may  be  collected  to  show  that  water  is  the  only 
product. 

404.  The  water  produced  in  this  mode,  is  not,  however, 
to  be  considered  as  a compound  of  the  two  gases,  but 


Analysis  of  Water. 


131 


only  of  their  bases,  for  the  light  and  caloric,  which  constitute  the  Sect- 11. 
gases,  escape,  in  considerable  part  during  the  combustion.  Every 
gas,  it  must  be  remembered,  has  at  least  two  ingredients  ; the  one, 
gravitating  matter,  which,  if  separated,  would  probably  exist  in  a 
solid  or  liquid  form  ; the  other,  an  extremely  subtile  fluid,  termed 
caloric  and  perhaps  electricity  and  light.  The  compound,  water,  is 
therefore  said  to  be  composed  of  hydrogen  and  oxygen,  the  bases  of 
the  gases,  and  not  of  the  hydrogen  and  oxygen  gases. 

405.  Water  may  be  decomposed  or  resolved  into  its  elements  by  Analysis  of 
a variety  of  processes,  the  most  important  of  which  are  the  fol-water» 
lowing  : 


Fie.  134. 


Fig.  134,  a,  is  a glass  retort, 
into  which  is  introduced  a 
given  weight  of  water  ; b b,  a 
small  furnace  through  which 
passes  the  earthen,  or  iron, 
tube  c c,  which  terminates  in 
the  spiral  pewter  tube  d d , 
immersed  in  water.  A given 
weight  of  pure  iron  coiled  up, 
is  introduced  into  the  tube  c, 
and  the  whole  made  red-hot  ; 
the  water  in  a is  then  made  to  boil,  and  the  vapour,  on  coming  into  contact  with 
the  red  hot  iron,  is  in  part  decomposed ; the  oxygen  is  retained  by  the  iron,  and 
the  hydrogen  escaping  through  the  tube  f , may  be  collected  as  usual.  Any  un- 
decomposed portion  of  water  is  condensed  in  the  worm  pipe  d , and  drops  into 
the  vessel  e. 


By  iron, 


Exp. 


After  this  experiment  the  iron  will  be  found  to  have  increased  in 
weight;  and  if  attention  be  paid  to  the  quantity  of  water  which  has 
collected  in  e,  and  to  the  weight  of  the  hydrogen  gas  evolved,  it  will 
be  found  that  the  weight  gained  by  the  iron,  added  to  that  of  the  hy- 
drogen, will  be  equal  to  the  weight  of  the  water  which  has  disap- 
peared. 

406.  The  processes,  by  which  the  elementary  parts  of  water  are 
separated  from  each  other,  and  are  both  obtained  in  an  aeriform 
state,  as  a mixture  of  hydrogen  and  oxygen  gases,  are  dependent  on 
the  agency  of  electricity. 

The  first  of  these  experiments  requires  for  its  performance  the  aid  Byelectri- 
of  a powerful  electrical  machine.  This  fact  was  the  discovery  of  a cityj 
society  of  Dutch  chemists  ; and  the  principal  circumstance  in  the  ex- 
periment, is  the  transmission  of  electrical  shocks  through  a confined 
portion  of  water.  If  these  shocks  be  sufficiently  strong,  bubbles  of 
air  will  be  formed  at  each  explosion,  and  the  mixed  gases  being  ex- 
ploded, the  water  will  rise  again  in  the  tube,  a very  small  quantity 
of  gas  remaining.  In  this  experiment  we  may  safely  infer,  that  the 
evolved  hydrogen  and  oxygen  gases  arise  from  decomposed  water. 

407.  The  decomposition  of  water  by  galvanic  electricity  is  a pro-  By  voltaic 
cess  singularly  adapted  to  demonstrate  the  fact  in  Fig  135-  electricity, 
a simple  and  elegant  manner,  since  it  exhibits  both 
the  oxygen  and  hydrogen  in  the  gaseous  form. 

Fig  135  represents  a section  of  an  apparatus  for  this  pur- 
pose. It  is  a glass  vessel  containing  water,  having  two  wires 
of  platinum  passing  through  its  bottom  : over  these  are  invert- 
ed the  tubes,  also  filled  with  water.  The  wires  are  connected 
with  a moderately  powerful  Voltaic  apparatus.  Oxygen  is 
evolved  at  the  positive  wire,  and  hydrogen  at  the  negative 
wire,  which  gases  rise  into  the  tubes,  and  it  is  seen  that  one 


132 


Chap.  III. 


By  living 
vegetables. 


Exp. 


Impurities 
of  water. 


Properties. 


Standard  oJ 

specific 

gravity. 


Hydrogen  and  Oxygen. 


volume  of  oxygen,  o,  and  two  volumes  of  hydrogen,  h , are  the  constant  results. 
If  these  gases  be  mixed  and  detonated,  pure  water  is  again  formed. 

408.  Another  mode  of  effecting  the  decomposition  of  water,  is  by 
the  action  of  living  vegetables,  either  entire  or  by  means  of  their 
leaves  only. 

Fill  a clear  glass  globe  with  water,  and  put  into  it  a number  of  green  leaves 
from  almost  any  tree  or  plant.  A sprig  or  two  of  mint  will  answer  the  purpose 
perfectly  well.  Invert  the  glass,  or  place  it,  with  its  mouth  downwards,  in  a 
vessel  of  water.  Expose  the  whole  apparatus  to  the  direct  light  of  the  sun, 
which  will  then  fall  on  the  leaves  surrounded  by  water.  Bubbles  of  air  will  soon 
begin  to  form  on  the  leaves,  and  will  increase  in  size,  till  at  last  they  rise  to  the 
top  of  the  vessel.  This  process  may  be  carried  on  as  long  as  the  vegetable  con- 
tinues healthy ; and  the  gas,  when  examined,  will  prove  to  be  oxygen  gas. 

In  this  experiment,  the  hydrogen  combines  with  the  plant  to  the 
nourishment  and  support  of  which  it  contributes,  while  the  oxygen  is 
set  at  liberty.  H.  1.253. 

409.  Water,  in  its  ordinary  state,  such  as  spring  and  river  water, 
is  always  so  far  contaminated  with  foreign  substances  as  to  be  unfit 
for  any  chemical  purposes,  and  frequently  as  will  be  more  fully 
shown  hereafter,  even  for  domestic  use.  Rain  water  is  much  more 
pure,  but  it  always  contains  a portion  of  carbonic  acid  and  of  the 
elements  of  atmospheric  air,  besides  appreciable  traces  of  vegetable 
or  animal  matter  ;*  to  the  latter  it  owes  its  property  of  becoming  pu- 
trid when  kept.  The  distinction  of  water  into  hard  and  soft  has 
reference  to  its  less  or  greater  purity.  The  impurities  of  water  are 
partially  separated  by  distillation. t 

410.  Distilled  Water , as  commonly  prepared,  always  affords  mi- 
nute traces  of  foreign  matter,  especially  when  subjected  to  Voltaic 
decomposition,  and  can  only  be  considered  as  perfectly  pure  when 
re-distilled  at  a low  temperature  in  silver  vessels. 

411.  Pure  water  is  transparent,  and  without  either  colour,  taste  or 
smell.  In  consequence  of  the  facility  of  obtaining  it  pure,  it  is  as- 
sumed as  a standard  to  which  the  relative  weight  of  all  other  bodies 
may  be  compared,  its  specific  gravity  being  called  = 1,000,  and 
hence  the  importance  of  estimating  its  weight  with  precision.  At 
the  temperature  of  62°  F.,  barom.  30,  a cubic  inch  of  distilled  water 
weighs  252.458  grains. t 


* The  existence  of  organic  matter  in  atmospheric  water,  has  been  ascribed  by  Eh- 
renberg  to  the  ova  of  a particular  class  of  infusoria,  and  to  them  the  presence  of  the 
substance  termed  pyrrhine.  There  is  evidence 
also  of  the  presence  of  salts  and  of  acids.  See 
Daubeny’s  Report  on  Water,  in  Vol.  v.  of  Reports 
of  Brit.  Assoc. 

+ This  process  is  usually  conducted  upon  the 
large  scale  in  a copper  boiler,  (Fig.  136,)  placed  ei- 
ther in  a portable  furnace,  or  set  in  brickwork,  ac- 
cording to  its  dimensions,  to  which  is  annexed  a 
head  b,  of  the  same  material,  or  of  pewter,  connect- 
ed with  a spiral  tube  or  worm,  which  is  immersed 
in  the  worm-tub,  or  refrigerator  d,  its  lower  end 
passing  out.  The  water  in  the  worm-tub  must  al- 
ways be  retained  of  a low  temperature  to  effect  the 
condensation  of  the  vapour  in  the  spiral  tube. 

t According  to  the  parliamentary  standard  of  Great  Britain,  the  pint  of  water  con- 
sists of  8750  grains  of  water  at  62°  F.  barometer  at  30  inches,  and  the  cubic  inch  of 
252,458  grains.  The  gallon  contains  277,274  cubic  inches,  or  70,000  grains  of  distilled 
water  ; the  pint  34,65925  inches,  or  8750  grains. 


Fig.  136. 


Water — absorbing  power  of.  133 

412.  At  the  temperature  of  32°  water  congeals  into  ice,  which,  if  Sect,  n. 
slowly  formed,  produces  needles  crossing  each  other  at  angles  of  60°  ice. 
and  120°.  The  specific  gravity  of  ice  is  0,94.  Exposed  to  the 

air,  ice  lo$es  considerably  in  weight  by  evaporation. 

413.  Water  is  susceptible  of  compression,  as  was  originally  shown  Compressi- 
by  Canton,  and  more  lately  by  Perkins,  who  has  estimated,  in  an  ble. 
ingenious  series  of  experiments,  the  rate  of  its  compression.^  If 
submitted  to  very  sudden  compression,  water  becomes  luminous,  as 

has  been  shown  by  Desaignes.f  According  to  Despretz  the  com- 
pression of  water  by  a force  equal  to  20  atmospheres,  causes  the 
evolution  of  ^g-th  part  of  a degree  of  heat. 

414.  Water  enters  into  combination  with  a variety  of  substances,  State  of 
and  is  retained  with  various  degrees  of  force.  Sometimes  it  is  con-  t°0™bina" 
tained  in  a variable  ratio,  as  in  ordinary  solution  ; in  other  com- 
pounds it  is  present  in  a fixed  definite  proportion,  as  in  its  union 

with  several  of  the  acids,  the  alkalies,  and  all  salts  that  contain  water 
of  crystallization.  These  combinations  have  been  termed  hydrates.  Hydrates. 

415.  Water,  which  has  been  exposed  to  the  atmosphere,  always  Water con- 
contains  a portion  of  air,  as  may  be  proved  by  boiling  it,  or  by  ex- tains  air. 
posing  it  under  the  exhausted  receiver  of  the  air-pump.  To  sepa- 
rate the  air,  the  water  must  be  boiled  for  about  two  hours.  It  absorbs 
oxygen  gas  in  preference  to  atmospheric  air  or  nitrogen,  and  when 

the  air  is  expelled  by  boiling,  the  last  portions  contain  more  oxygen 
than  those  first  given  off.! 

416.  Every  gas  is  absorbed  by  water,  which  has  been  deprived  of  Absorption 
all  or  the  greatest  part  of  its  air  by  long  boiling.  The  quantity,  of  gases  by 
however,  which  water  is  capable  of  absorbing,  varies  considerably  water‘ 
with  respect  to  the  different  gases.  Those  gases,  of  which  only  a 

small  proportion  is  absorbed,  require  violent  and  long  continued  agi- 
tation in  contact  with  water.  H.  1.253.  In  the  common  process  of 
manufacturing  soda-water  a large  quantity  of  carbonic  acid  gas  is 
absorbed  by  the  water,  and  an  additional  portion  is  mechanically 
united  with  it  by  powerful  compression. § 


* Phil.  Trans.  1820.  tThenard,  TraiU  de  Chimies  i.  432. 

t Humboldt  and  Gay-Lussac,  Jour,  de  Phys.  1805. 

§ The  following  table  from  Henry’s  Chemistry  shows  the  absorbability  of  different 
gases  by  water  deprived  of  all  its  air  by  ebullition. 

100  cubic  inches  of  such  water,  at  the  mean  temperature  and  pressure,  absorb  of 


Sulphuretted  hydrogen 

Dalton  and  Henry. 

100  cubic  inches 

Saussure. 

253 

Carbonic  acid 

- 

- 

100  “ 

CC 

166 

Nitrous  oxide  - 

. 

„ 

100 

Ct 

76 

Olefiant  gas 

... 

- 

12,5  “ 

a 

15,3 

Oxygen 

- 

- - 

3,7  “ 

u - 

6,5 

Carbonic  oxide  - 

. 

. 

1,56  “ 

a 

6.2 

Nitrogen  - 

. 

. 

1,56  “ 

“ - 

4,1 

Hydrogen 

- 

- 

1,56  “ 

“ - 

4,6 

The  estimate  of  Saus?ure  is  in  general  too  high.  That  of  Dalton  and  Henry  for  ni- 
trous oxide  is  considerably  beyond  the  truth,  according  to  the  experiments  of  Davy.  T. 


134 


Chap.  Ill- 


Properties. 


Actiou  of 
metals, 


Use. 


Discovery. 


How  ob- 
tained. 


Nitrogen , 

Binoxide  or  Peroxide  of  Hydrogen. 

Composition. 

By  Wght.  By  Vol. 

Chem.  Symb.  Hyd.  Oxy.  Equiv.  Hyd.  Oxy.  <S p.  Gr. 

H-t-20,orH  I or  I eq. -f-16  or2eq.  = 17  100  100  1.452. 

Discovered  by  Thenard,  in  the  year  1818. 

There  are  two  oxides  of  barium  ; when  the  peroxide  of  that 
metal  is  put  into  a dilute  acid,  oxygen  gas  is  set  at  liberty,  and  the 
peroxide  is  converted  into  protoxide  of  barium  or  baryta,  which  com- 
bines with  the  acid.  The  oxygen  which  is  set  free,  unites  with  the 
hydrogen  of  the  water,  and  brings  it  to  a maximum  of  oxidation.* 

417.  The  peroxide  of  hydrogen  is  a colourless  transparent  liquid 
without  odour.  It  acts  as  a caustic  upon  the  skin,  thickens  the  sali- 
va, and  tastes  like  certain  metallic  solutions.  It  destroys  the  colour 
of  litmus  and  turmeric  paper.  It  continues  liquid  at  all  degrees  of 
cold  to  which  it  has  hitherto  been  exposed. 

At  the  temperature  of  59°  F.  it  is  decomposed,  being  converted 
into  water  and  oxygen  gas.  It  effervesces  from  the  escape  of  oxy- 
gen at  59°  F.  and  the  sudden  application  of  a higher  temperature, 
as  of  212°  F.  gives  rise  to  such  a rapid  evolution  of  gas  as  to  cause 
an  explosion.  All  the  metals  except  iron,  tin,  antimony  and  telluri- 
um, have  a tendency  to  decompose  it,  converting  it  into  oxygen  and 
water ; especially  when  the  metals  have  been  previously  reduced  to 
a state  of  minute  division.  The  metals  which  have  a strong  affinity 
for  oxygen  are  at  the  same  time  oxidized. 

418.  It  has  been  employed  to  remove  the  black  spots  that  paint- 
ings acquire  from  the  conversion  of  carbonate  of  lead  into  sulphuret. 
It  converts  the  black  sulphuret  into  white  sulphate  of  lead. 


Section  III.  Nitrogen. 

Symb.  Sp.  Gr.  Equiv. 

N.  0.9727  air  = 1 By  Vol.  100 

14.15  Hyd.=  1 “ Wght.  14-15 

419.  This  was  first  recognised  as  a distinct  aeriform  fluid  by 
Rutherford,  in  1772.  It  may  be  obtained  by  heating  phosphorus  in 
a confined  portion  of  dry  air,  which  consists  of  nitrogen  and  oxygen  ; 
the  phosphorus  absorbs  the  latter,  and  the  former  gas  remains. 

Phosphorus  is  placed  in  a small  metallic  cup,  supported  on  Fig.  137. 

a stand  on  the  shelf  of  the  pneumatic  trough,  and  covered 
with  a bell  glass  the  moment  the  phosphorus  is  kindled. 

Eight  or  ten  grains  of  phosphorus  may  be  taken  for  every 
100  cubic  inches  of  air;  and  the  cup  containing  the  phos- 
phorus must  be  raised  to  a proper  height,  as  the  water  rises 
afterwards  in  the  jar  to  supply  the  place  of  the  oxygen  re- 
moved ; after  repeated  washing  with  a solution  of  potassa, 
it  may  be  considered  as  pure.  Or  by  inverting  a jar  full  of 
common  air  over  a mixture  of  equal  weights  of  iron  filings  and  sulphur  made 
into  a paste  with  water.  But  this  process  requires  much  time. 

A quicker  process  consists  in  filling  a bottle,  about  one  fourth,  with  a solution 
of  binoxide  of  nitrogen,  in  liquid  protosulphate  of  iron,  or  with  liquid  sulphur- 


* From  the  complicated  nature  of  the  process  it  is  not  likely  to  be  the  subject  of 
experiment  with  the  beginner.  For  details  consult  the  original  memoir  of  Thenard 
Ann.  de  Chim.  el  de  Phys.  vol.  viii.  ix.  x.  ; Ann.  of  Philos,  vol.  xiii.  and  xiv. ; Tbe- 
nard’s  TraUi  de  Chim.  and  Turner’s  Elem.  163. 


135 


Properties , fyc. 

et  of  calcium,  and  agitating  it  with  the  air,  which  fills  the  rest  of  the  bottle.  Sect.  HI. 
During  the  agitation,  the  thumb  must  be  firmly  placed  over  the  mouth  of  the 
bottle ; and,  when  removed,  the  mouth  of  the  bottle  must  be  immersed  in  a cup 
full  of  the  same  solution, ^which  will  supply  the  place  of  the  absorbed  air.  The 
agitation  and  admission  of  fluid  must  be  renewed,  alternately,  as  long  as  any 
absorption  takes  place. 

Nitrogen  mixed  with  carbonic  ’ acid,  may  be  procured  from  the  other  pro- 
lean part  of  flesh  meat,  which  may  be  put  into  a gas  bottle,  along  eesses. 
with  very  dilute  nitric  acid.  By  a heat  of  about  100°,  the  gas  is 
disengaged,  and  may  be  collected  over  water.  Its  source  is  the  ani- 
mal substance.^ 

420.  One  of  the  easiest  methods  of  preparing  nitrogen,  is  to  pass  a current  of 
chlorine  gas  through  liquid  ammonia  ; the  ammonia  is  decomposed,  hydrochlor- 
ic acid  is  formed  from  the  union  of  the  chlorine  and  the  hydrogen  of  the  am- 
monia, and  its  nitrogen  liberated.  The  arrangement  of  the  apparatus  is  shown 
in  the  cut  annexed. 1 Emmett  has  described  another  process,  which  consists  in 


Fig.  138. 


fusing  nitrate  of  ammonia  in  a retort  with  fragments  of  zinc.  The  metal  de- 
composes the  nitric  acid  of  the  salt,  and  nitrogen  and  ammonia  are  given  off; 
when  collected  over  water,  the  latter  gas  is  absorbed.  The  emission  of  the  gas 
can  be  regulated  by  using  a small  cylinder  of  zinc  attached  to  a rod  passing 
through  the  tubulure  of  the  retort,  which  can  be  raised  or  depressed  into  the 
fused  salt.t 

421.  This  gas  is  fatal  to  animal  life  and  was,  on  this  account,  Derivation 
named  by  Lavoisier  Azote  or  Azotic  gas,  derived  from  the  Greek  of  azote, 
privative  a and  £<wry,  life.  This  being  but  a negative  property,  the 

term  nitrogen  has  been  substituted,  because  one  of  the  most  impor- 
tant properties  of  its  base  is,  that  by  union  with  oxygen,  it  composes 
nitric  acid.  It  is  not  inflammable  ; and  a lighted  taper  is  extin- 
guished by  it.  Even  phosphorus  in  a state  of  active  inflamma- 
tion is  instantly  extinguished  by  it. 

422.  When  mixed  with  pure  oxygen  gas,  in  the  proportion  of  four 
parts  to  one  of  the  latter,  it  composes  a mixture  resembling  atmos- 
pheric air  in  all  its  properties,  and  in  which  a taper  will  burn. 

One  hundred  cubic  inches  weigh  30.1650  grains.  T. 

423.  That  nitrogen  is  not  an  element,  but  itself  a compound,  has  Composi- 
been  long  suspected,  and  various  attempts  have  been  made  to  dis-  tion  of  ni- 
cover  its  ingredients.  Berzelius  has  inferred  that  nitrogen  is  com-lrogen> 
pounded  of  oxygen  and  an  unknown  base.  This  base,  however,  is 
purely  hypothetical ; and  has  never  yet  been  exhibited  in  a separate 

state.  Berzelius  has  proposed  for  it  the  name  of  nitricum. 

424.  Nitrogen  and  oxygen. — When  nitrogen  and  oxygen  gases  General 

—— ; ; — ; — view  of  the 

It  appears  from  the  remarks  of  Daubeny,  that  nitrogen  gas  is  given  off  from  many  compounds 
thermal  springs.— Report  on  mineral  and  thermal  waters  in  vol.  v.  of  Rep.  Brit,  of  nitrogen 
Assoc  39.  andoxy- 

+ Johnson’s  report  in  Rep.  Brit.  Assoc.  1331-2.  455.  gen.  • 

t Roy.  Instit.  Jour.  1 384. 


136 


Chap.  III. 


Atmosphe- 
ric air. 


Weight. 


Barometer. 


Density  of 
the  atmos- 
phere indi- 
cated. 


Nitrogen  and  Oxygen. 


are  mingled  together,  no  combination  ensues.  The  result  is  a sim- 
ple mixture  of  the  two  gases,  which  do  not,  like  inelastic  fluids, 
separate  on  standing,  but  remain  diffused  through  each  other  for  an 
indefinite  length  of  time.  When,  however,  either  one  or  both  of 
these  elements  is  in  a condensed  state,  they  unite  and  form  com- 
pounds, distinguished  by  very  striking  properties.  According  to  the 
proportions  in  which  the  oxygen  and  nitrogen  exist  in  these  com- 
pounds, their  qualities  undergo  a remarkable  variation  ; so  that  from 
two  elementary  bodifes,  variously  united,  we  have  several  compounds, 
totally  unlike  each  other  in  external  qualities,  as  well  as  in  their 
chemical  relations. 

425.  Nitrogen  and  oxygen  are  the  two  most  important  constitu- 
ents of  the  atmosphere  ; the  thin,  transparent  and  elastic  fluid  which 
surrounds  our  planet. 

426.  The  atmosphere  reaches  to  a considerable  height,  probably 
about  45  miles.*  It  may  be  diminished  in  volume  to  a great  extent 
by  compression. 

That  air  is  a ponderous  body,  was  first  suspected  by  Galileo, 
who  found  that  a copper  ball,  in  which  the  air  had  been  condensed, 
weighed  heavier  than  when  the  air  was  in  its  ordinary  state  of  ten- 
sion. The  fact  was  afterwards  demonstrated  by  Toricelli. 

In  1643,  he  filled  a glass  tube,  three  feet  long,  and  closed  at  one 
end  with  quicksilver,  and  inverted  it  in  a basin  of  the  same  fluid  ; 
he  found  that  the  mercury  fell  about  six  inches,  so  that  the  atmos- 
phere appeared  capable  of  counterbalancing  a column  of  mercury 
30  inches  in  height.  The  empty  space,  in  the  upper  part  of  the 
tube,  has  hence  been  called  the  Torricellian  vacuum,  and  is  the 
most  perfect  that  can  be  formed. 

Paschal  and  Toricelli  afterwards  observed,  that  upon  ascending  a 
mountain,  the  quicksilver  fell  in  the  tube,  because  there  was  less  air 
above  to  press  upon  the  surface  of  the  metal  in  the  basin ; and  thus 
a method  of  measuring  the  heights  of  mountains  by  the  barometer , 
as  the  instrument  is  now  called,  was  devised. 

428.  The  barometer  indicates,  by  its  rise  and  fall,  a corresponding 
change  in  the  density  of  the  atmosphere.!  At  the  surface  of  the 
earth,  the  mean  density  or  pressure  is  considered  equal  to  the  sup- 
port of  a column  of  quicksilver  30  inches  high.! 


* See  Wollaston  “ on  the  Finite  Extent  of  the  Atmosphere Bost.  Jour.  1.  15. 
t From  causes  at  present  not  understood,  the  pressure  varies  at  the  same  place. 
On  this  depend  the  indications  of  the  barometer  as  a weather-glass  ; the  weather  is 
commonly  fair  and  calm  when  the  barometer  is  high,  and  usually  wet  and  stormy 
when  the  mercury  falls. 

Inches. 


t At  1000  feet  above  the  surface  the  column  falls  to  28,91 


2000 

27,86 

3000 

26.85 

4000. 

25.87 

5000 

24,93 

1 Mile 

24,67 

2 

20,29 

3 

16,68 

4 

13,72 

5 

11,28 

in 

4,24 

15 

1,60 

20 

0,96 

See  Camb.  Me- 


chanics, page  351 . 


Eudiometry. 


137 


428.  The  general  mechanical  properties  of  the  air  are  best  illus-  Sect,  hi. 
trated  by  the  air  pump the  construction  of  which  much  resembles  Air-pump, 
that  of  the  common  pump  used  for  raising  water,  excepting  that  all 

the  parts  are  more  accurately  and  nicely  made,  the  object  being  to 
exhaust  the  air  as  completely  and  expeditiously  as  possible.! 

429.  The  specific  gravity  of  atmospheric  air,  at  mean  temper-  Specific 
ature  and  pressure,  that  is,  the  thermometer  being  at  60°,  and  the  SravltY- 
barometer  at  30  inches,  is,  usually  considered  as  ==  1.  It  is  about 

815  times  as  light  as  its  bulk  of  water,  100  cubical  inches  weighing 
31,0117  grains. 

430.  Atmospheric  air  has  already  been  stated  to  consist  essen- 
tially of  oxygen  and  nitrogen  gases  : whether  it  should  be  consider- 
ed a mere  mixture  or  a chemical  compound,  is  a question  which  has 

been  much  discussed.!  The  oxygen  seems  to  be  the  only  ingre- C^emicaJ 
dient  on  which  the  effects  of  the  air,  as  a chemical  agent,  depend,  pendent  on 
Hence  combustible  bodies  burn  in  atmospheric  air,  only  in  conse-  oxygen, 
quence  of  the  oxygen  gas  which  it  contains  ; and  when  this  is  ex- 
hausted, air  is  no  longer  capable  of  supporting  combustion.  Its 
analysis  is  satisfactorily  demonstrated  by  the  action  of  heated  mer- 
cury, but  the  process  is  tedious. § By  exposure,  during  12  days  to  Lavoisier’s 
mercury  heated  in  a retort,  a given  quantity  of  atmospheric  air  was^ePQtrg‘ 
found  to  be  diminished  in  bulk,  and  to  have  lost  its  property  of  sup- 
porting combustion.  The  mercury  was  changed  into  red  scaly  par- 
ticles, and  it  had  acquired  an  increase  of  weight.  When  these  red 
particles  were  submitted  to  heat,  in  a retort,  oxygen  gas  was  evolved 
equal  in  bulk  to  what  the  air  had  lost  in  the  first  part  of  the  experi- 
ment. 

431.  There  are  various  ways  of  learning  the  proportion  which 
the  oxygen  bears  to  the  nitrogen ; and  as  the  relative  fitness  of  the 
air  for  breathing  has  sometimes  been  considered  as  depending  upon 
the  quantity  of  oxygen  contained  in  a given  volume,  the  instruments 

used  in  these  experiments  have  been  called  eudiometers.  Eudiome- 

432.  From  facts  already  stated  it  is  obvious,  that  if  atmospheric  try- 
air,  mixed  with  a certain  quantity  of  hydrogen,  be  detonated  by  the 
electric  spark,  the  absorption  will  be  proportionate  to  the  quantity  of 
oxygen  present. 

When  100  measures  of  pure  hydrogen  are  mixed  with  100  of 
pure  oxygen,  the  diminution  of  bulk  after  detonation  will  amount  to 
150  parts,  that  is,  one  volume  of  oxygen  requires  for  its  saturation 
two  of  hydrogen.  If  we  introduce  into  the  graduated  detonating 
tube  (Fig.  106)  300  measures  of  common  air,  and  200  of  pure  hy- 
drogen, there  will  remain,  after  detonation,  305  measures ; so  that 
195  measures  will  have  disappeared,  of  which  one  third  may  be  es- 
timated as  pure  oxygen  ; hence  300  parts  of  air  have  thus  lost  65  of 
oxygen,  or  about  21  per  cent. 

433.  The  general  rule,  therefore,  for  estimating  the  purity  of  air  General 
by  hydrogen  gas  may  be  stated  as  follows: — Add  to  3 measures  of  Wie- 
the air  under  examination  2 measures  of  pure  hydrogen  ; detonate ; 


* See  Frontispiece.  t See  statement  in  Turner , 171. 

t See  Camb.  Mechanics , page  403.  § See  Lavoisier’s  Elements,  chap.  iii. 

18 


138 


Nitrogen  and  Oxygen . 

ChaP- in-  and,  when  the  vessel  has  cooled,  observe  the  absorption ; divide  its 
amount  by  3,  and  the  quotient  is  the  quantity  of  oxygen. 

434.  Upon  the  same  principle,  detonation  of  mixtures  of  oxygen 
other^  ases  anc^  hydrogen  often  resorted  to,  with  a view  of  ascertaining  the 
ascertain8-68  Parity  of  those  gases. 

ed-  To  ascertain  the  purity  of  hydrogen,  it  may  be  detonated  with 

excess  of  pure  oxygen. 

Thus,  if  we  add  100  of  pure  oxygen  to  100  of  hydrogen,  and  detonate,  there 
will  be  a diminution  equal  to  two  thirds,  or  150  parts  if  the  hydrogen  be  pure. 
If,  however,  we  suppose  100  of  pure  oxygen,  mixed  with  100  of  hydrogen,  to 
produce,  after  detonation,  a residue  of  80  measures,  the  diminution  will  then 
nave  been  only  120  measures,  of  which  two  thirds,  or  80  measures,  are  hydro- 
gen ; so  that  the  inflammable,  gas  will  have  contained  20  per  cent,  of  some 
other  gaseous  body,  not  condensable  by  detonation  with  hydrogen.1* 

435.  This  mode  of  ascertaining  the  purity  of  atmospheric  air 

Eudiomc-  was  firsl  resorted  to  by  Volta,  and  it  is  susceptible  of  great  accura- 
ter  of  Volta.  , , J , 1 i j + 

cy,  since  pure  hydrogen  and  pure  oxygen  are  easily  procured.! 


* For  a particular  description  of  several  points  iu  eadiometry,  see  Faraday’s  Chem. 
Manip . sect.  xvii.  paragraph  919,  &c. 

t In  the  eudiometer  of  Ure,  the  atmospheric  air,  the  most  elastic  and  economical  of 
Ur^enJiuma.  all  springs,  is  employed  to  receive  and  deaden  the  recoil.  This  eudiometer  consists 
ler-  of  a glass  syphon  (Fig.  139),  having  an  interior  diameter  of  from  2-lOtbs  to  4-10ths 

of  an  inch.  Its  legs  are  of  nearly  equal  length,  each  being  from  six  to  nine  inches 
long.  The  open  extremity  is  slightly  funnel-shaped,  the  other  hermetically  sealed ; 
and  has  inserted  near  it,  by  the  blow  pipe,  two  platinum  wires. 

The  outer  end  of  the  one  wire  is  incurvated  across,  so  as  nearly 
to  touch  the  edge  of  the  aperture ; that  of  the  other  is  formed 
into  a little  hoolc.  to  allow  a small  spherical  button  to  be  at- 
tached to  it  when  the  electrical  spark  is  to  he  transmitted.  The 
two  legs  of  the  syphon  are  from  one-fourth  to  one-half  inch  as- 
under. The  sealed  leg  is  graduated  by  introducing  successive- 
ly equal  weights  of  mercury  from  a measure  glass  tube.  Sev- 
en ounces  troy  and  66  grains,  occupy  the  space  of  a cubic  inch  ; 
and  34  1-4  grains  represent  part  °f  that  volume.  The 
other  leg  may  be  graduated  also,  though  this  is  not  necessary. 

To  use  this  instrument,  we  first  fill  the  whole  syphon  with  mercury  or  water ; the 
open  leg  is  then  plunged  into  a pneumatic  trough,  and  any  convenient  quantity  of  the 
gases  is  introduced  from  a glass  measure  tube  containing  them  in  determinate  pro- 
portions. Applying  the  finger  to  the  orifice  we  next  remove  it  from  the  trough,  like  a 
simple  tube,  and  by  a little  dexterity  transfer  the  gas  into  the  sealed  leg  of  the  sy- 
phon. When  we  conceive  enough  has  beeu  passed  up,  the  finger  is  removed  and  the 
mercury  brought  to  a level  in  both  legs,  either  by  the  addition  of  a few  drops,  or  by 
the  displacement  of  a portion,  by  thrusting  down  into  it  a small  cylinder  of  wood. 
We  now  ascertain,  by  careful  inspection,  the  volume  of  included  gas.  Applying  the 
forefinger  again  to  the  orifice,  so  as  also  to  touch  the  end  of  the  platinum  wire,  we 
then  approach  the  ball  to  the  electrical  machine,  and  transmit  a spark,  but  a slight 
push  or  pressure  on  the  tip  of  the  finger  is  felt,  even  when  the  gas  is  in  considerable 
quantity  and  of  a strongly  explosive  power.  After  explosion  on  gradually  sliding 
the  finger  to  one  side  and  admitting  the  air,  the  mercurial  column  in  the  sealed  leg 
will  rise  more  or  less  above  that  in  the  other.  The  equilibrium  is  then  restored  by 
adding  mercury,  when  we  read  off,  without  any  reduction,  the  true  resulting  volume 
of  gas.  As  two  inches  or  more  of  air  should  always  be  left  between  the  finger  and 
the  mercury,  this  atmospheric  column  serves  as  a perfect  recoil  spring,  enabling  us 
to  explode  very  large  quantities  without  danger. 

We  may  analyze  the  residual  gaseous  matter,  by  introducing,  either  a liquid  or  solid 
re-agent.  We  first  fill  the  open  leg  nearly  to  the  brim  with  quicksilver,  and  then 
place  over  it  the  substance  whose  action  on  the  gas  we  wish  to  try.  If  liquid,  it  may 
be  passed  round  into  the  sealed  leg  among  die  ga6;  but  if  solid  the  gas  must  be 
brought  round  into  the  open  leg,  its  orifice  having  been  previously  closed  with  a cork 
or  stopper.  After  a proper  interval  the  gas  having  been  transferred  back  into  the 
graduated  tube,  the  change  of  its  volume  may  be  accurately  determined.— Ure's  Diet. 
A\0—Edin.  Phil.  Trans.  1818.— See,  also,  Faraday,  p.  434.  Several  new  eudiome- 
ters have  been  described  by  Hare,  in  the  Amcr.  Jour,  of  Sci.  vols.  ii.  and  x- 


139 


Composition  of  Air . 

436.  Instead  of  electricity,  spongy  platinum  may  be  employed  for  Sect,  hi. 
causing  the  union  of  oxygen  and  hydrogen  gases  ; and  while  its  in-  Analysis 
dications  are  very  precise,  it  has  the  advantage  of  producing  the  ef-  plati- 
fect  gradually  and  without  detonation.  The  most  convenient  mode 

of  employing  it  with  this  intention  is  the  following  : 

A mixture  of  spongy  platinum  and  pipe-clay,  in  the  proportion  of  about  Process, 
three  parts  of  the  former  to  one  of  the  latter,  is  made  into  a paste  with  water, 
and  then  rolled  between  the  fingers  into* * *  a globular  form.  In  order  to  pre- 
serve the  spongy  texture  of  the  platinum,  a little  hydrochlorate  of  ammonia 
is  mixed  with  the  paste  ; and  when  the  ball  has  become  dry,  it  is  cautiously 
ignited  at  the  flame  of  a spirit-lamp.  The  sal  ammoniac,  escaping  from  all 
parts  of  the  mass,  gives  it  a degree  of  porosity  which  is  peculiarly  favourable 
to  its  action.  The  ball,  thus  prepared,  should  be  protected  from  dust,  and  be 
heated  to  redness  just  before  being  used. 

To  insure  accuracy,  the  hydrogen  employed  should  be  kept  over 
mercury  for  a few  hours  in  contact  with  a platinum  ball  and  a piece 
of  caustic  potassa.  The  first  deprives  it  of  traces  of  oxygen  which 
it  commonly  contains,  and  the  second  of  moisture  and  hydrosulphu- 
ric  acid.  The.  analysis  must  be  performed  in  a mercurial  trough. 

The  time  required  for  completely  removing  the  oxygen  depends  on 
the  diameter  of  the  tube.  If  the  mixture  is  contained  in  a very 
narrow  tube,  the  diminution  does  not  arrive  at  its  full  extent  in  less 
than  twenty  minutes  or  half  an  hour  ; while  in  a vessel  of  an  inch 
in  diameter,  the  effect  is  complete  in  the  course  of  five  minutes.^ 

437.  When  nitric  oxide  gas,  (binoxide  of  nitrogen)  and  atmos-  method? § 
pheric  air  are  mixed,  there  is  a production  of  nitrous  acid,  in  conse- 
quence of  the  union  of  oxygen  with  the  oxide  ; and  if  the  mixture 

be  made  over  water,  an  absorption  ensues.  Upon  this  principle 
this  gas  was  used  in  eudiometrical  experiments,  by  Priestley  and 
Cavendish.!  There  are,  however,  several  sources  of  error  for 
which,  and  the  precautions  required  to  ensure  accuracy,  see  Binoxide 
of  Nitrogen , ! (454.) 

438.  If  a stick  of  phosphorus  be  confined  in  a portion  of  atmos-  Lavoi- 

pheric  air  it  will  slowly  absorb  the  oxygen  present.  The  rapid  sier’s,&c. 
combustion  of  the  same  substance  may  also  be  conveniently  resort- 
ed to.  These  eudiometrical  methods  were  used  by  Lavoisier, 
Berthollet,  and  Seguing  _ Uniformity 

439.  The  analyses  of  atmospheric  air,  collected  at  various  eleva-  in  compo- 
tions  and  in  different  latitudes,  show  that  the  proportion  of  oxygen  sitionofair. 
is  between  20  and  21  volumes,  and  of  nitrogen  79  or  80.  The  av- 
erage of  a number  of  analyses  by  Hare’s  eudiometer,  gave  the  pro- 
portion of  oxygen  at  20,66  per  cent.  The  air  which  Gay-Lussac 
brought  from  an  altitude  of  21,735  feet  above  the  earth,  had  the 

same  composition  as  that  collected  near  its  surface.  But  Faraday 
found  a decided  difference  between  the  air  from  the  arctic  regions 
and  that  of  London.  Dalton  has  inferred  that  the  proportion  of 
oxygen  to  nitrogen  in  the  air  on  the  surface  of  the  earth,  is  not  pre- 


* See  Henry’s  Essay  in  Philos.  Trans.  1824. — Henry’s  Chemistry,  1.237. 

t Phil.  Trans.  17 83.  t See  Dalton’s  Remarks,. Phil.  Mag.  Vol.  xxviii.  For 

the  details  of  this  process  see  Henry’s  Chemistry,  vol,  1.  p.  312,  edit.  10th. 

§ Ann.  de  Chim.  tom.  ix.  and  xxxiv. 


140 


Chap.  III. 


Carbonic 
acid  in  air. 


Water  in 
air, 


Its  quanti- 
ty- 


Slate  in 
which  eonv 
ponents  of 
the  air  ex- 
ist, 


Dalton’s 

▼iew, 


Graham’s 

experi- 

ments. 


Nitrogen  and  Oxygen. 

cisely  the  same  at  all  places  and  times,  and  that  in  elevated  regions, 
the  proportion  is  somewhat  less. 

The  miasmata  of  marshes  and  the  effluvia  of  infected  places,  are 
supposed  to  owe  their  noxious  qualities  to  some  peculiar  subtle  prin- 
ciple, and  not  to  a deficiency  of  oxygen.* 

440.  Though  oxygen  and  nitrogen  are  the  essential  component 
parts  of  atmospheric  air,  it  contains  other  substances,  which,  however, 
may  be  regarded  as  adventitious,  and  the  quantity  of  which  is  liable 
to  vary  : of  these,  carbonic  acid  and  aqueous  vapour  are  the  most  im- 
portant and  constant.  The  quantity  of  the  former  may  usually  be 
considered  as  amounting  to  less  than  1 per  cent. 

441.  The  presence  of  aqueous  vapour  in  the  atmosphere  is  shown 
in  a variety  of  ways,  but  most  easily  by  exposing  to  it  certain  de- 
liquescent substances  which  liquefy  and  increase  in  weight,  in  con- 
sequence of  its  absorption. t 

The  quantity  of  water  contained  in  air  and  gases  is  subject  to  va- 
riation. From  the  experiments  of  Saussure  and  Dalton,  it  appears 
that  100  cubic  inches  of  atmospheric  air  at  57°,  are  capable  of  re- 
taining 0,35  grains  of  watery  vapour ; in  this  state  the  air  may  be 
considered  at  its  maximum  of  humidity:  it  would  also  appear  that 
all  the  gases  take  up  the  same  quantity  of  water  when  under  similar 
circumstances,  and  that  it  consequently  depends,  not  upon  the  den- 
sity or  composition,  but  upon  the  bulk  of  the  gaseous  fluid. 

442.  Berthollet  considered  that  the  elements  of  the  air  are  retain- 
ed together  by  chemical  attraction ; but  Dalton  maintains  that  they 
are  merely  mechanically  mixed,  and  proved  that  gases  mingle  me- 
chanically that  have  no  attraction,  and  that  even  carbonic  acid  rises 
through  a small  tube  into  a bottle  of  hydrogen  placed  above  it, 
though  much  heavier,  a corresponding  quantity  of  hydrogen  des- 
cending into  the  carbonic  acid  bottle.  This  proves  a power  of  diffu- 
sion among  the  gases.  Dalton  concluded  that  particles  of  the  same 
gases  repel  each  other,  but  that  those  of  different  gases  do  not,  and 
that  one  gas  acts  as  a vacuum  to  another,  though  they  diffuse  them- 
selves more  slowly  through  each  other  than  in  a vacuum. 

443.  Graham  has  ascertained  that  each  gas  has  a diffusiveness  pe- 
culiar to  itself,  which  is  inversely  proportional  to  the  square  root  of 
its  density,  and  has  drawn  up  tables  representing  their  diffusive  pow- 
er, air  being  taken  as  a standard  of  comparison. t He  used  a tube 
with  the  gas  under  examination,  open  at  one  end,  and  closed  with 
plaster-of-paris  at  the  other,  the  diffusion  taking  place  readily 
through  the  pores  of  this  substance  when  moderately  dry  ; it  also 
takes  place  through  membranes,  small  cracks  in  glass  vessels,  and 
through  numerous  porous  bodies.^  From  all  these  considerations, 


♦According  to  Prout  there  was  a peculiar  state  of  the  air  during  the  prevalence  of 
the  cholera  in  London,  in  1832.  See  Reports  of  Brit.  Assoc.  1832. 

+ As  the  gases  in  general,  unless  artificially  dried,  also  contain  vapour,  it  is  neces- 
sary, in  delfcate  experiments,  and  in  ascertaining  their  specific  gravity,  to  take  this 
ingredient  into  the  account,  or  to  separate  it  by  proper  means,  such  as  exposure  to  very 
deliquescent  substances,  among  which  fused  chloride  of  calcium  is  especially  useful. 

t Phil.  Trans.  Edin.  1831. 

§ See  Mitchell’s  experiments  in  Amer.  Jour.  Med.  Sci • vii.  36. 


141 


Protoxide  of  Nitrogen . 

Dalton’s  view  of  the  constitution  of  the  air  is  now  generally  adop-  Sect,  in. 
ted.  R.  54. 

444.  Hygroscopes  and  Hygrometers  are  instruments  which  show 

the  presence  of  water  in  the  air,  its  variation  in  quantity,  and  its  Hygrorne. 
actual  quantity  existing  in  a given  bulk  of  air  at  any  given  time.  ters. 
Daniell's  hygrometer  shows  the  constituent  temperature  of  the  mois- 
ture in  the  atmosphere,  by  its  precipitation  upon  a cold  surface.! 

445.  Since  oxygen  is  necessary  to  combustion,  to  the  respiration  Lossofox- 
of  animals,  and  to  various  other  natural  operations,  by  all  of  which  ygen,  how 
that  gas  is  withdrawn  from  the  air,  it  is  obvious  that  its  quantity  compeusa- 
would  gradually  diminish,  unless  the  tendency  of  those  causes  were 
counteracted  by  some  compensating  process.  The  only  source  by 

which  oxygen  is  known  to  be  supplied,  is  the  action  of  growing  veg- 
etables. A healthy  plant  absorbs  carbonic  acid  during  the  day,  ap- 
propriates the  carbonaceous  part  of  that  gas  to  its  own  wants,  and 
evolves  the  oxygen  with  which  it  was  combined.  During  the  night, 
indeed,  an  opposite  effect  is  produced.  Oxygen  gas  then  disappears, 
and  carbonic  acid  is  eliminated ; but  it  follows  from  the  experiments 
of  Priestley,  Davy,  and  Daubeny,  that  plants  during  24  hours  yield 
more  oxygen  than  they  consume.  Whether  living  vegetables  make 
a full  compensation  for  the  oxygen  removed  from  the  air  by  the  pro- 
cesses above  mentioned,  is  uncertain. 

Nitrogen  and  Oxygen.  Protoxide  of  Nitrogen — Nitrous  Oxide. 

Composition. 

Symb.  Sp.  Gr.  Nit.  Oxy.  Chem.  Equiv. 

N + OorN  1.5239  Air  =1  By  Vol.  100  + 50  100 

22.15  Hyd.  =1  “ Wght.  14.15  + 8 22.15 

446.  This  gas  was  termed,  by  its  discoverer,  Priestley,  dephlogisti- 
cated  nitrous  air;  by  the  Dutch  chemists  gaseous  oxide  of  azote. 

It  is  obtained  by  several  processes,  but  that  most  usually  adopted  is 
the  following.  The  salt  obtained  by  neutralizing  nitric  acid  with 
carbonate  of  ammonia,  called  Nitrate  of  Ammoniat  is  heated  in  a 
glass  retort.  When  all  the  salt  is  liquefied,  it  should  be  kept  gently 
simmering,  avoiding  violent  ebullition.  The  temperature  should  not  Processf 
be  raised  above  500°  F.  If  a white  cloud  appears  within  the  retort, 

due  to  some  of  the  salt  subliming  undecomposed,  the  heat  should 
be  checked. § The  management  of  the  heat  is  to  be  carefully  at- 
tended to ; when  the  heat  is  too  great,  the  gas  is  apt  to  be  im- 
pure. 

447.  The  gas  may  be  collected  over  water  and  allowed  to  stand  Collected 
an  hour  or  two  before  it  is  used,  during  which  time  it  will  deposit  a over  watel» 


t See  Quart.  Jour.  Sci.  vols.  viii.  ix.  x. 
t See  Nitrate  of  Ammonia. 

§ A chauffer  with  ignited  charcoal  affords  the  best  heat,  and  the  retort  is  less  liable 
to  be  broken  than  when  a lamp  is  employed.  An  iron  or  tin  plate  will  be  found  use- 
ful to  check  the  ebullition  if  too  great,  as  it  can  be  interposed  between  the  chauffer 
and  the  retort,  and  withdrawn  at  pleasure. 


142 


Ch.ip.  III. 


Theory  of 
the  process 


Properties. 


May  be  re- 
spired. 


Supports 

combus- 

tion. 


Detonates 
with  hydro- 
gen. 


Nitrogen  and  Oxygen. 


white  substance  and  become  transparent.  When  a large  quantity  is 
wanted,  it  may  be  received  in  a gasholder,  and  much  gas  will  be 
saved  if  the  vessel  be  filled  with  water  which  has  been  once  used 
for  the  same  purpose. 

448.  The  products  of  this  operation,  when  carefully  conducted, 
are  water  and  protoxide  of  nitrogen.  The  nature  of  the  change 
will  be  understood  by  comparing  the  composition  of  nitrate  of  am- 
monia with  that  of  the  products  derived  from  it.  These,  in  round 
numbers,  are  as  follows : 

Nitric  Acid.  Ammonia.  Water.  Prot.  of  NiWogen . 


Nitrogen  14  or  1 eq.  Nitrogen  14  or  1 eq.  Hyd.  3 or  3 eq.  Nit.  28  or  2 eq. 

Oxygen  40  or  5 eq.  Hydrogen  3 or  3 eq.  Oxy.  24  or  3 eq.  Oxy . 16  or  2 eq. 


54 


17 


27 


44 


The  same  expressed  in  symbols  is 

N+50;  N+3H;  | 3(H+0) ; 2(N+0). 

The  hydrogen  in  the  ammonia  takes  so  much  oxygen  as  is  suffi- 
cient for  forming  water,  and  the  residual  oxygen  converts  the  nitro- 
gen both  of  the  nitric  acid  and  of  the  ammonia  into  protoxide  of  ni- 
trogen: 71  grains  of  the  salt  will  thus  yield  44  grains  of  protoxide 
of  nitrogen  and  27  of  water. 

449.  Protoxide  of  nitrogen  is  a colourless  gas,  which  does  not 
affect  the  blue  vegetable  colours,  even  when  mixed  with  atmospheric 
air.  Kecently  boiled  water,  which  has  cooled  without  exposure  to 
the  air,  absorbs  nearly  its  own  bulk  of  it  at  60°  F.  and  gives  it  out 
again  unchanged  by  boiling.  The  solution,  like  the  gas  itself,  has 
a faint  agreeable  odour  and  sweet  taste.  The  action  of  water  affords 
a ready  means  of  testing  its  purity ; removing  it  readily  from  all 
other  gases,  such  as  oxygen  and  nitrogen,  which  are  sparingly  ab- 
sorbed by  that  liquid. 

450.  Davy  discovered  that  this  gas  may  be  taken  into  the  lungs 
with  safety,*  and  that  it  supports  respiration  for  a few  minutes.  A 
few  deep  inspirations  of  it  are  followed  by  feelings  of  excitement, 
similar  to  the  early  stages  of  intoxication.  The  experiment,  how- 
ever, cannot  be  made  with  impunity  by  all  persons,  especially  by 
those  who  are  liable  to  a determination  of  blood  to  the  head.f 

451.  Protoxide  of  nitrogen  supports  combustion,  and  a taper  in- 
troduced into  it  has  its  flame  much  augmented  and  surrounded  by  a 
purplish  halo.  Phosphorus  and  sulphur,  when  introduced  in  a state 
of  vivid  ignition  into  this  gas,  burn  with  the  same  appearance  nearly 
as  in  oxygen ; but,  if  when  put  into  the  gas,  they  are  merely  burn- 
ing dimly,  they  do  not  decompose  it  and  are  extinguished,  so  that 
they  may  be  melted  in  the  gas,  or  even  touched  with  a red-hot  wire 
without  inflaming,  (but  when  wire  intensely  heated,  or  made  white- 
hot,  is  applied,  the  phosphorus  burns,  or  rather  detonates,  with  pro- 
digious violence.  H.)  Charcoal,  and  many  of  the  metals,  also  de- 
compose protoxide  of  nitrogen  at  high  temperatures. 

452.  A mixture  of  this  gas  with  an  equal  bulk  of  hydrogen  gas 
detonates,  on  applying  a lighted  taper,  or  passing  an  electric  spark, 


* Researches  on  the  nitrous  oxide • 

4 See  report  of  remarkable  cases  ia  Amer.  Jour.  vol.  v. 


Binoxide  of  Nitrogen. 


143 


and  is  decomposed  also  by  spongy  platinum  at  common  tempera-  sect.  ni. 
tures.  The  product  of  the  combustion  is  the  same  as  when  oxygen  ~ 
gas  or  atmospheric  air  is  used.  The  protoxide  is  decomposed  ; the 
combustible  matter  unites  with  its  oxygen,  and  the  nitrogen  is  set 
free. 

453.  At  a red  heat  this  gas  is  decomposed  and  converted  into  Decompo- 
nitrogen,  oxygen  and  nitrous  acid.*  It  was  analyzed  by  Davy,  by  sltlon- 
means  of  hydrogen  gas.  He  mixed  39  measures  of  the  former  with 
40  measures  of  hydrogen,  and  fired  the'  mixture  by  the  electric 
spark.  Water  was  formed  ; and  the  residual  gas,  which  amounted 
to  41  measures,  had  the  properties  of  pure  nitrogen.  As  40  mea- 
sures of  hydrogen  require  20  of  oxygen  for  combustion,  it  follows 
that  39  volumes  of  the  protoxide  of  nitrogen  contain  41  of  nitrogen 
and  20  of  oxygen.  According  to  Gay-Lussac's  law  of  gaseous  com- 
bination, it  may  be  inferred  that  protoxide  of  nitrogen  contains  its  Analysis, 
own  bulk  of  nitrogen  and  half  its  volume  of  oxygen.  The  analy- 
sis of  this  compound  by  Henry,!  by  means  of  carbonic  oxide  gas, 
has  proved  beyond  a doubt  that  this  is  the  exact  proportion.  Now, 

100  cubic  inches  of  nitrogen  gas  weigh  - 30.1650  grains 

50  do.  oxygen  - - - 17.0936  “ 

These  numbers  added  together  amount  to  - • 47.2586 

which  must  be  the  weight  of  100  cubic  Inches  of  the  protoxide  ; and 
its  specific  gravity  is,  therefore,  1.5239.  Its  composition  by  weight 
is  determined  by  the  same  data,  being  17.0936  of  oxygen  to  30.1650 
of  nitrogen,  or  as  8 to  14.117,  nearly  the  number  already  sta- 
ted. T. 


Syrrib. 
N+20  or  N 


Binoxide  of  Nitrogen — Nitric  Oxide. 

Composition. 

Sp.  Gr.  Nit.  Oxy 

1,0375  air=l  By  Vol. 


15.75 


air  = 
Hyd.: 


Wght. 


too 

14.15 


Chem.  Equiv. 
— 200 
= 30.15 


454.  This  gas,  discovered  by  Hales,  was  first  examined  by  Priest- 
ley, and  called  by  him  nitrous  air  a term  afterwards  changed  to  ni- 
trous gas,  then  to  nitric  oxide,  and  more  lately  to  Binoxide  of  Nitro- 
gen, which  last  appears  to  be  its  most  appropriate  title.  It  is  more 
generally  known,  however,  under  the  name  of  nitrous  gas. 

455.  It  is  usually  obtained  by  presenting  certain  substances  to  ni- 
tric acid,  which  abstract  a portion  of  its  oxygen,  leaving  the  remain- 
ing elements  in  such  proportions  as  to  constitute  the  gas  in  ques-  laP^d^ >- 
tion  ; for  this  purpose  copper  may  be  put  into  a gas  bottle,  (Fig.  87) 


* For  experiments  of  this  Fig.  140. 

kind  the  following  simple 
apparatus  may  be  used  : It 
consists  of  two  bladders, 

I Fig.  140,)  one  of  which  is  /y 
filled  with  the  gas,  and  the  ff/y 

other  empty,  attached  to  the  

extremities  of  a porcelain  tube  which  traverses  the  body  of  a furnace, 
ders  are  supplied  with  stop-cocks,  and  the  gas  is  squeezed  from  one  to 
when  the  tube  is  red  hot. 

t Ann.  of  Phil.  viii.  299,  N.  S. 


The  blad- 
the  other 


144 


Chap.  III. 


Theory  of 
the  process. 


Effect  of 
oxygen, 


Exp. 


Exp. 


Analysis. 


Properties. 


Nitrogen  and  Oxygen. 

with  nitric  acid,  diluted  with  thrice  its  bulk  of  water;  an  action  en- 
' sues,  red  fumes  are  produced,  and  there  is  a copious  evolution  of 
the  gas,  which  may  be  collected  and  preserved  over  water.  The 
first  portions  should  be  rejected.  It  is  presently  recognised  by  the 
red  fumes  which  it  produces  when  brought  into  the  contact  of  air. 
During  this  process  part  of  the  nitric  acid  gives  oxygen  to  the  cop- 
per; and  passes  to  the  state  of  binoxide  of  nitrogen,  the  remaining 
acid  unites  with  the  oxide  of  copper,  and  composes  a nitrate  of  that 
metal. 

Quicksilver  may  be  substituted  for  the  copper  ; but  in  the  latter 
case  it  will  be  found  necessary  to  apply  heat  to  the  materials. 

450.  When  mixed  with  oxygen  gas  red  fumes  arise,  heat  is  evolv- 
ed, a diminution  takes  place,  and  if  the  two  gases  be  in  proper  pro- 
portion, and  perfectly  pure,  they  disappear  entirely.  The  product  of 
this  union  is  possessed  of  acid  properties,  which  may  be  shown  by 
the  following  experiments. 

1 . Paste  a slip  of  litmus  paper  within  a glass  jar,  near  the  bottom  ; and  into  the 
jar,  filled  with  and  inverted  in  water,  admit  as  much  of  the  gas,  previously  well 
washed,  as  will  displace  the  water  below  the  level  of  the  paper.  The  colour 
of  the  litmus  will  remain  unchanged  ; but  on  adding  oxygen  gas  it  will  be  im- 
mediately reddened. 

2.  Puss  up  into  ajar  filled  with  the  vegetable  infusion,  (56  Note)  a quantity  of 
oxygen  gas  sufficient  to  displace  about  one  half  of  the  infusion  ; to  this  admit 
biuoxide  of  nitrogen,  absorption  and  reddening  will  ensue. 

457.  Binoxide  of  nitrogen  is  rather  heavier  than  common  air. 
It  is  partially  resolved  into  its  elements  by  being  passed  through  red- 
hot  tubes.  A succession  of  electric  sparks  has  a similar  effect.  It 
is  converted  into  protoxide  of  nitrogen  by  substances  which  have  a 
strong  affinity  for  oxygen.  Davy  ascertained  its  composition  by  the 
combustion  of  charcoal.*  Two  volumes  of  the  binoxide  yielded  one 
volume  of  nitrogen,  and  about  one  of  carbonic  acid,  whence  it 
was  inferred  to  consist  of  equal  measures  of  oxygen  and  nitrogen 
gases  united  without  any  condensation.  Gay-Lussac  also  proved 
that  this  proportion  is  exact.  He  decomposed  100  measures  of  the 
gas,  by  heating  potassium  in  it;  when  50  measures  of  pure  nitro- 
gen were  left,  and  the  potassa  formed  corresponded  to  50  measures 
of  oxygen.  The  same  fact  has  been  lately  proved  by  Henry. t 
Hence,  as 

50  cubic  inches  of  oxygen  gas  weigh  - - 17.0936  grains. 

50  do.  nitrogen  - - - 15.0825  “ 

100  cubic  inches  of  the  binoxide  must  weigh  32.17C1 

Its  composition  stated  at  page  143  is  drawn  from  these  facts.  Its 
density  ought  to  be  1.0375,  which  closely  agrees  with  the  direct  ex- 
periments of  Davy,  Thomson,  and  Berard.  T. 

453.  When  washed  with  water  it  is  not  acid.  Water  absorbs 
the  binoxide  sparingly ; 100  measures  of  that  liquid,  cold  and  re- 
cently boiled,  takeup  about  11  of  the  gas.  It  extinguishes  most 
burning  bodies  ; but  phosphorus  readily  burns  in  it  if  introduced  in 
intense  ignition.  It  is  quite  irrespirable,  exciting  strong  spasms  of 
the  glottis,  as  soon  as  an  attempt  is  made  to  inhale  it.  The  experi- 
ment, however,  is  a dangerous  one. 


* Elem.  Chem.  Phil.  p.  200. 


t Ann.  of  Phil.  N.  S.  viii-  299. 


Hyponitrous  Acid , 


145 


459.  It  is  decomposed  by  exposure  to  almost  all  bodies  that  attract  s,ec-  nL 
oxygen  ; thus  iron  filings  decompose  it,  and  become  oxidized,  afford- Decompose 
ing  a proof  of  the  presence  of  oxygen  in  it.  During  this  process,  hon, 
water,  ammonia,  and  protoxide  of  nitrogen  are  generated.  Mixed 

with  sulphurous  acid,  it  is  decomposed,  and  this  acid  is  changed  into 
the  sulphuric,  but  not  unless  water  is  present.  With  an  equal  bulk 
of  hydrogen,  it  forms  a mixture  which  cannot  be  made  to  explode, 
but  which  is  kindled  by  contact  with  a lighted  candle,  and  burns 
rapidly  with  a greenish  white  flame,  water  and  pure  nitrogen  gas 
being  the  sole  products.  The  action  of  freshly  ignited  spongy  platb 
num  on  a mixture  of  hydrogen  and  binoxide  of  nitrogen  gases  leads 
to  the  slow  production  of  water  and  ammonia. 

460.  From  the  formation  of  red  coloured  acid  vapours,  whenever  Use  in  Eu« 
binoxide  of  nitrogen  and  oxygen  are  mixed,  these  gases  detect  the  pre-  lome  rL 
sence  of  each  other  ; and  since  the  product  is  wholly  absorbed  by  wa- 
ter, either  of  them  may  be  entirely  removed  from  any  gaseous  mixture 

by  adding  a sufficient  quantity  of  the  other.  Priestley,  who  first  ob- 
served this  fact,  supposed  that  combination  takes  place  between  them 
in  one  proportion  only;  and  inferring  on  this  supposition,  that  a 
given  absorption  must  always  indicate  the  same  quantity  of  oxygen, 
he  was  led  to  employ  binoxide  of  nitrogen  in  Eudiometry.  But  in 
this  opinion  he  was  mistaken.  Dalton  and  Gay-Lussac  have  described 
the  precautions  which  are  required  to  insure  accuracy.^ 

Hyponitrous  Acid. 

Composition. 

Symb.  Nit..  Oxy.  Equiv. 

By  Vol.  100  + 150 

N+30  or  N “ Wght.  14.15  + 24  = 38.15 

461.  On  adding  binoxide  of  nitrogen  in  excess  to  oxygen  gas,  process> 
confined  in  a giass  tube  over  mercury,  Gay-Lussac  found  that  100 
measures  of  the  latter  combine  with  400  of  the  former  forming  an  acid 
which  unites  with  the  potassa.  The  compound  so  formed  is  hypo- 
nitrous acid. 

462.  The  anhydrous  liquid  acid  is  colourless  at  0°  F.  and  green  at  Properties, 
common  temperatures.  It  is  so  volatile,  that  in  open  vessels  the 

green  fluid  wholly  and  rapidly  passes  off  in  the  form  of  an  orange 
vapour,  which  is  said  to  have  a density  of  1.72.  On  admixture  with 
water  it  is  converted  into  nitric  acid  and  binoxide  of  nitrogen,  the 
latter  escaping  with  effervescence ; but  when  much  nitric  acid  is 
present,  the  hyponitrous  is  changed  into  nitrous  acid,  which  imparts 


* Dalton  in  Ann.  of  Phil.  x.  38;  and  further  directions  have  been  published  MelhodofGay, 
by  Henry  in  his  -Elements.  Instead  of  employing  a narrow  tube,  such  as  is  com-  Lussac. 
monly  used  for  measuring  gases,  Gay  -Lussac  advises  that  100  measures  of  air  should 
be  introduced  into  a very  wide  tube  or  jar,  and  that  an  equal  volume  of  binoxide  of 
nitrogen  should  then  be  added.  The  red  vapours,  which  are  insfa&tl'y  produced  ; dis-, 
appear  very  quickly  ; and  the  absorption  after  half  a minute,  or  y minute  at  the  most,, 
may  be  regarded  as  complete.  The  residue  is  then  transferred  into  a graduated  tube 
and  measured.  The  diminution  almost  always,  according  to  Gay-Lussac,  amounts  to 
84  measures,  one-fourth  of  which  is  oxygen.  Gay-Lussac  has  applied  this. process  to 
the  analysis  of  various  mixed  gasbs,  in  which  the  oxygep  was  sometimes  in  a. greater, 
at  others  in  a less  proportion  than  in  the  atmosphere,  and  the  indications  were  al  - 
ways correct.  For  other  details  see  Turner’s  Elements,  177,  and  Dana  on,  Nitrous , 

Gas,  Amer.  Jour.,  vii.  338. 

19 


146 


I 

Chap.  III. 


Action  of 
sulphuric 
acid. 


Nitrous 
acid  gas. 


Exp. 


Not  easily- 
examined. 


;Properties. 


Liquid  ni- 
trous acid. 


From  ni- 
trate of 
lead. 


Nitrogen  and  Oxygen. 

_ several  shades  of  colour,  orange,  yellow,  green,  and  blue,  according 
to  its  quantity.  One  equivalent  of  hyponitrous  and  one  of  nitric 
acid,  yield  two  equivalents  of  nitrous  acid  : thus  N-)-30  and  N-}-50 
contain  the  elements  for  forming  2(N-f-40). 

463.  Hyponitrous  acid  does  not  unite  directly  with  alkalies,  being 
then  resolved  principally  into  nitric  acid  and  binoxide  of  nitrogen ; 
but  the  hyponitrites  of  the  alkalies  and  alkaline  earths  may  be  ob- 
tained by  heating  the  corresponding  nitrates  to  a gentle  red  heat. 

464.  Hyponitrous  acid  forms  with  water  and  sulfuric  acid 
a crystalline  compound,  which  is  generated  in  large  quantity  during 
the  manufacture  of  sulphuric  acid,  and  the  production  of  which  is  an 
essential  part  of  that  process.  It  is  generated  whenever  moist  sul- 
phurous acid  gas  and  nitrous  acid  vapour  are  intermixed,  being 
instantly  deposited  in  the  form  of  white  acicular  crystals.  T.  179. 

Nitrous  Acid. 

Composition. 

Symb.  Nit.  Oxy.  Equiv. 

By  Vol.  100  + 200 

N+40  or  N “ Wglit.  14.15  + 32  = 46.15 

465.  When  binoxide  of  nitrogen  is  presented  to  oxygen,  the  two 
gases  combine,  and  a new  gaseous  compound  of  a deep  orange  colour 
results. 

Into  a large  glass  globe,  or  other  convenient  vessel,  previously  filled  with  wa- 
ter, introduce  sufficient  nitrous  gas  to  displace  about  two  thirds  of  the  water.  On 
passing  into  it  oxygen  gas  the  vessel  will  become  filled  with  deep  orange  coloured 
nitrous  acid  gas. 

This  compound  is  absorbed  both  by  quicksilver  and  water,  so  that 
to  preserve  it  for  examination,  we  are  obliged  to  resort  to  exhausted 
glass  vessels.  When  we  thus  mix  two  volumes  of  binoxide  of  ni- 
trogen with  one  volume  of  oxygen,  the  gases  become  condensed  to 
one  third  their  original  volume,  and  form  nitrous  acid  vapour. 

466.  This  gas  supports  the  combustion  of  the  taper,  of  phosphorus, 
and  of  charcoal,  but  extinguishes  sulphur.*  100  measures  of  nitrous 
acid  vapour  contain  100  of  nitrogen  gas  and  200  of  oxygen.  The  spe- 
cific gravity  of  this  vapour  ought  to  be  3.1775,  formed  of  0.9727  the 
sp.  gr.  of  nitrogen-f-2.2048  twice  the  sp.  gr.  of  oxygen. 

467.  Nitrous  acid  may  exist  in  the  liquid  as  well  as  in  the  gase- 
ous form.  To  form  liquid  nitrous  acid,  its  vapour  may  be  con- 
densed by  a freezing  mixture.  It  is  readily  absorbed  by  water  ; the 
water  becomes  first  green,  then  blue,  and  finally  an  orange  colour, 
more  or  less  deep.  The  latter  may  be  brought  to  the  state  of  green 
or  blue  by  adding  more  or  less  water.  Hence  the  colour  depends 
partly  on  the  circumstance  of  density ; but  there  can  be  little  doubt 
that  it  is  materially  affected  also  b'y  the  proportions  of  nitric,  nitrous, 
and  hyponitrous  acids,  which  according  to  Gay-Lussac,  compose  ni- 
trous acid,  as  it  is  ordinarily  obtained  in  a liquid  state.  H.  1.  321. 

468.  It  may  be  procured  by  exposing  nitrate  of  lead  carefully 
dried  to  a heat  sufficient  to  decompose  the  salt.  The  nitric  acid  of 
the  salt  is  resolved  into  nitrous  acid  and  oxygen ; and  if  the  products 


* It  reddens  litmus  paper,  has  a sour  taste,  a strong  smell,  and  turns  animal  sub- 
stances yellow. 


Nitric  Acid. 


147 


are  received  in  vessels  kept  moderately  cool,  the  greater  part  of  the  Sect.  m. 
former  condenses  into  a liquid.  This  substance  was  first  obtained 
by  Gay-Lussac. 

469.  The  liquid  anhydrous  acid  is  powerfully  corrosive,  has  a Properties, 
strong  acid  taste  and  pungent  odour,  and  is  of  a yellowish  orange 
colour.  Its  density  is  1.451.  It  remains  liquid  at  ordinary  tempe- 
ratures and  pressure,  and  boils  at  82°  F.  Exposed  to  the  air  it  eva- 
porates with  great  rapidity,  forming  the  common  nitrous  acid  vapours, 
which,  when  once  mixed  with  air  or  other  gases,  require  an  intense 

cold  to  condense  them. 

470.  Nitrous  acid  is  a powerful  oxidizing  agent,  readily  giving  Oxidizes, 
oxygen  to  the  more  oxidable  metals,  and  to  most  substances  which 

have  a strong  affinity  for  it.  The  acid  is  decomposed  at  the  same 
time,  being  commonly  changed  into  binoxide  of  nitrogen,  though 
sometimes  the  protoxide  and  even  pure  nitrogen,  gases  are  evolved. 

When  transmitted  through  a red  hot  porcelain  tube,  it  suffers  decom- 
position, and  a mixture  of  oxygen  and  nitrogen  gases  is  obtained. 

When  nitrous  acid  is  mixed  with  a considerable  quantity  of  water,  Action  of 
it  is  instantly  resolved  into  nitric  acid,  which  unites  with  the  water,  ^ater* 
and  binoxide  of  nitrogen  which  escapes  with  effervescence. 


Nitric  Acid . 

Composition. 

Symb.  Nit.  Oxy.  Equiv. 

VJ-Lrn  N ByVol.  100  + 250 

N+oOor  N “ Wght.  14.15  4-  40  = 54.15 

471.  If  a succession  of  electric  sparks  be  passed  through  a mixture 
of  oxygen  and  nitrogen  gases  confined  in  a glass  tube  over  mercury, 
a little  water  being  present,  the  volume  of  the  gases  will  gradually 
diminish,  and  the  water  after  a time  will  be  found  to  have  acquired 
acid  properties.  On  neutralizing  the  solution  with  potassa,  or  what 
is  better,  by  putting  a solution  of  pure  potassa,  instead  of  water,  into 
the  tube,  a salt  is  obtained  which  possesses  all  the  properties  of  the 
nitrate  of  potassa  (nitre.)  This  experiment  was  performed  by  Ca- 
vendish in  1785,  who  inferred  from  it  that  nitric  acid  is  composed  of 
oxygen  and  nitrogen. 

The  nitric  acid  may  be  formed  more  conveniently  by  adding  bi- 
noxide of  nitrogen  slowly  over  water  to  an  excess  of  oxygen  gas.  It 
cannot  exist  in  an  insulated  state.  The  most  simple  form  under 
which  chemists  have  hitherto  procured  nitric  acid  is  in  solution  with 
water.  It  is  usually  obtained  by  the  distillation  of  purified  nitre 
with  sulphuric  acid,  of  which  materials  different  proportions  are  em- 
ployed. 

Into  a glass  retort,  which  may  be  either  tubulated  or  not,  put  four  parts  by 
weight  of  nitrate  of  potassa,  reduced  to  a coarse  powder,  and  pour  upon  it  three 
parts  of  concentrated  sulphuric  acid.  Apply  a tubulated  receiver  of  large  capa- 
city between  which  and  the  retort,  an  adopter  may  be  interposed ; these  junc- 
tures being  luted  with  a mixture  of  pipe-clay,  sifted  sand,  and  cut  tow  or  flax. 
To  the  tubulure  of  the  receiver,  a glass  tube  may  be  fixed  by  means  of  the  fat 
lute,*  and  may  terminate  in  another  receiver,  containing  a small  quantity  of 


Nitric  acid 
formed. 


Usual 
process  for 
obtaining 
nitric  acid. 


* Formed  by  heating  perfectly  dry  and  finely  sifted  tobacco  pipe  clay,  with  painters' 
drying  oil. 


148 


Chap.  III. 


On  the 
large  scale. 


Purification 
of  nitric 
acid. 


Preparation  of 
nitrous  acid,  or 
aquafortis 


Nitrogen  and  Oxygen. 

If  the  operator  wishes  to  collect  the  gaseous  products  also,  this  second  receiver 
should  be  provided  with  a tubulure,  to  which  a bent  pipe  may  be  luted,  termi- 
nating under  one  of  the  inverted  funnels  in  the  shelf  of  the  pneumatic  trough. 
Apply  heat  to  the  retort,  through  the  intervention  of  the  sand-bath.  The  first 
product  that  passes  into  the  receiver,  is  generally  of  a red  colour,  and  of  a smok- 
ing quality.  These  appearances  gradually  diminish;  and  if  the  materials  used 
were  clean,  the  acid  will  come  over  pale,  and  even  colourless.  Afterwards  it 
gradually  re-assumes  a red  colour,  and  smoking  property;  which  appearances  go 
on  increasing  till  the  end  of  the  operation  ; and  the  whole  product  mingled  to- 
gether, has  either  a yellow  or  an  orange  colour,  according  to  the  temperature 
employed.  H.  1.318. 

472.  The  nitric  acid  of  commerce,  which  is  generally  red  and 
fuming  in  consequence  of  the  presence  of  binoxide  of  nitrogen,  is 
procured  by  the  distillation  of  two  parts  of  nitre  with  one  of  sulphu- 
ric acid  ; these  proportions  afford  about  one  part  of  orange -coloured 
nitric  acid  of  the  specific  gravity  of  1.48.* 

473.  The  nitric  acid  of  commerce,  as  usually  obtained  is  impure. 
It  frequently  contains  portions  of  sulphuric  and  hydrochloric  acid. 
The  former  is  derived  from  the  acid  which  is  used  in  the  process  ; 
and  the  latter  from  sea-salt,  which  is  frequently  mixed  with  nitre. 
These  impurities  may  be  detected  by  adding  a few  drops  of  a solution 
of  chloride  of  barium  and  nitrate  of  silver  to  separate  portions  of  ni- 
tric acid,  diluted  with  three  or  four  parts  of  distilled  water.  If  chlo- 
ride of  barium  cause  a cloudiness  or  precipitate,  sulphuric  acid  must 
be  present ; if  a similar  effect  be  produced  by  nitrate  of  silver,  the 
presence  of  hydrochloric  acid  may  be  inferred.  Nitric  acid  is  puri- 
fied from  sulphuric  acid  by  redistilling  it  from  a small  quantity  of 
nitrate  of  potassa,  with  the  alkali  of  which  the  sulphuric  acid  unites, 
and  remains  in  the  retort.  To  separate  hydrochloric  acid,  it  is  ne- 
cessary to  drop  a solution  of  nitrate  of  silver  into  the  nitric  acid  as 
long  as  a precipitate  is  formed,  and  draw  off  the  pure  acid  by  distil- 
lation.! 


* Upon  the  large  scale  112  lbs.  of  nitre,  and  56  of  sulphuric  acid  yield  from  50  to  52 
lbs.  of  nitric  acid.  Some  manufacturers  employ  three  parts  of  nitre  and  two  of  sul- 
phuric acid,  and  the  London  Pharmacopoeia  directs  equal  weights,  by  which  a nearly 
colourless  nitric  acid  is  afforded. 

t The  distillation  of  nitric  acid  may  be  conducted  upon  the  small  scale  in  a tabulated 
glass  retort  a,  with  a tubulated  receiver  b,  passing  into  the  bottle  c,  (Fig.  141.)  The 
requisite  heat  is  obtained  by  the  lamp  d)  and  the  whole  apparatus  supported  by  the 
brass  stands  with  sliding  rings  c e. 

Fig.  141.  Fig.  142. 


The  manufacturer  who  prepares  nitric  acid  upon  a large  scale,  generally  emplovs  dis- 
tillatory vessels  of  stone  ware.  Fig.  142  represents  the  arrangement  of  the  distillatory 
apparatus,  employed  at  Apothecaries’  Hall,  London,  for  the  production  of  common 
aqua-fortis  : it  consists  of  an  iron  pot,  set  in  brick-work,  over  afire-place  ; an  earthen- 
ware head  is  luted  upon  it,  communicating  with  two  receivers  of  the  same  material, 
furnished  with  earthen  ware  stop  cocks,  the  last  of  which  has  a tube  of  safety  dipping 
into  a basin  of  water. 


149 


Nitric  Acid — Effect  of  Light. 

For  pharmaceutical  purposes,  the  ordinary  acid  is  generally  suffi-  Sect.m. 
ciently  pure.  If,  however,  pure  nitre,  and  pure  sulphuric  acid  be 
employed  in  its  production,  and  the  latter  not  in  excess,  there  is  little 
apprehension  of  impurity  in  the  resulting  acid. 

474.  Liquid  nitric  acid  is  heavier  than  water,  in  the  proportion  of  Specific 
1.5  or  upwards  to  1.  The  specific  gravity  of  real  nitric  acid,  which  gravity, 
cannot,  however,  be  obtained  separately,  may  be  calculated  at  1.75. 

In  its  heaviest  form,  it  still  contains  a portion  of  water,  which  is  es- 
sential to  its  existence  in  a liquid  state.  In  acid  of  the  sp.  gr.  1.5  the 
water  amounts  to  20  per  cent.  It  possesses  acid  properties  in  an  em- 
inent degree.  A few  drops  of  it  diluted  with  a considerable 
quantity  of  water  form  an  acid  solution,  which  reddens  litmus  paper 
permanently.  It  unites  with  and  neutralizes  alkaline  substances, 
forming  with  them  salts  which  are  called  nitrates. 

475.  Nitric  acid  is  usually  coloured  by  nitrous  acid. 

To  expel  which,  put  the  acid  into  a retort  to  which  a receiver  is  applied,  the  Coloured 
two  vessels  not  being  luted,  but  joined  merely  by  paper.  Apply  a very  gentle  by  nitrous 
heat  for  several  hours  to  the  retort,  changing  the  receiver  as  soon  as  it  becomes  acid  gas. 
filled  with  red  vapours.  The  nitrous  gas  will  thus  be  expelled,  and  the  nitric 
acid  will  remain  in  the  retort  limpid  and  colourless.  It  must  be  kept  in  a bottle 
secluded  from  light.  H.  327. 

476.  Nitric  acid  emits  white  fumes  when  exposed  to  the  air,  and  Decompo- 
is  extremely  sour  and  corrosive.  It  effects  the  decomposition  of  ani-  matters^*1 
mal  matters.  The  cuticle  and  nails  receive  a permanent  yellow 

stain  when  touched  with  it ; and  if  applied  to  the  skin  in  sufficient 
quantity  it  acts  as  a powerful  cautery,  destroying  the  organization  of 
the  part  entirely. 

477.  It  boils  at  248°  F.,  and  may  be  distilled  over  without  any  Boiling 
essential  change.  An  acid,  weaker  than  1.42,  is  strengthened  byp01nt’ 
being  boiled;  while  an  acid,  stronger  than  1.42,  becomes  weaker  by 
boiling.  All  the  varieties  of  nitric  acid,  therefore,  are  brought,  by 
sufficient  boiling,  to  the  specific  gravity,  1.42,  which  appears  to  be 

the  most  energetic  combination  of  acid  and  water. 

478.  Nitric  acid  may  be  frozen  by  cold.  The  temperature  at  Freezing, 
which  congelation  takes  place,  varies  with  the  strength  of  the  acid. 

The  strongest  acid  freezes  at  about  50°  below  zero.  When  diluted  with 
half  its  weight  of  water,  it  becomes  solid  at — 1 F.  By  the  addition 
of  a little  more  water,  its  freezing  point  is  lowered  to— 45°  F.  Strong 
nitric  acid  absorbs  moisture  from  the  atmosphere  ; in  consequence  Absorbs 
of  which  it  increases  in  weight,  and  diminishes  in  specific  gravity.  mmsture- 

479.  When  two  parts  of  the  acid  are  suddenly  diluted  with  one  of  Mixed  with 
water,  an  elevation  of  temperature  is  produced  to  about  120°  F.  ; water, 
and  the  admixture  of  58  parts  by  weight  of  acid  of  specific  gravity  turePr!ses. 
1.50  with  42  parts  of  water,  both  at  60°  F.,  gives  a temperature  of 

140°. * When  more  water  is  added  to  this  diluted  acid,  its  tempera- 
ture is  reduced.  Snow  or  ice  added  to  the  cold  dilute  acid  is  in- 
stantly liquefied  and  an  intense  degree  of  cold  produced. 

480.  Wffieri  very  concentrated  it  becomes  coloured  by  exposure  to  Effect  of 
the  sun’s  light,  passing  first  to  a straw  colour,  and  then  to  a deep  solar  ]i§ht* 
orange.  This  effect  is  produced  by  the  union  of  the  light  of  the  sun 


* Ure.  See  table  of  strength  of  diluted  acid  in  Appendix. 


150 


Chap.  III. 

Affords  ox- 
ygen. 

Decompos- 
ed by  com- 
bustibles, 


Exp. 
Action  on 
phospho- 
rus, 


Exp. 


Caution. 

Metals, 


and  by  a 
red  heat. 


Nitrogen  and  Oxygen. 

with  oxygen,  in  consequence  of  which  the  proportion  of  that  princi- 
. pie  to  the  nitrogen  is  diminished.  By  exposing  it  to  the  sun’s  rays 
in  a gas  bottle,  the  bent  tube  of  which  terminates  under  water,  oxy- 
gen gas  may  be  procured.  H.  i.  321. 

481.  This  acid  retains  its  oxygen  with  but  little  force,  and  hence 
is  much  employed  by  chemists  for  bringing  bodies  to  their  maximum 
of  oxidation.  It  is  decomposed  by  all  combustible  bodies,  which  are 
oxygenized  by  it,  with  more  or  less  rapidity  in  proportion  to  their 
affinity  for  oxygen. 

Poured  on  perfectly  dry  and  powdered  charcoal  it  excites  the  com- 
bustion of  the  charcoal,  which  becomes  red-hot,  and  emits  an  im- 
mense quantity  of  fumes. 

Its  action  on  phosphorus  is  often  extremely  violent,  and  great  Fig*  143. 
care  should  be  taken  to  avoid  accident.  A few  pieces  of  phos-  1 

phorus  may  be  placed  in  the  bottom  of  a tall  and  strong  glass, 
and  the  acid  be  poured  upon  it  from  a vessel  attached  to  the  end 
of  a long  rod  of  wood.*  (Pig.  143.) 

All  vegetable  substances  are  decomposed  by  it.  In 
general  the  oxygen  of  the  nitric  acid  enters  into  direct 
combination  with  the  hydrogen  and  carbon  of  those 
compounds,  forming  water  with  the  former,  and  car- 
bonic acid  with  the  latter.  This  happens  remarkably 
in  those  compounds  in  which  hydrogen  and  carbon  are 
predominant,  as  in  alcohol  and  the  oils.  ==k£===4=» 

It  inflames  essential  oils  when  suddenly  poured  on  them. 

Into  a gallipot,  placed  upon  a hearth  and  containing  about  a table  spoonful  of 
oil  of  turpentine,  pour  about  half  the  quantity  of  the  strong  acid,  previously 
mixed  with  a few  drops  of  sulphuric  acid.  The  moment  the  aeids  come  in  con- 
tact with  the  turpentine,  a large  quantity  of  dense  smoke  will  be  produced,  often 
accompanied  with  flame.  The  acid  should  be  poured  from  a bottle  tied  to  (he 
end  of  a long  stick,  otherwise  the  operator’s  eyes  may  be  severely  injured. 

482.  It  is  also  decomposed  by  metals,  with  different  phenomena, 
according  to  the  affinity  of  each  metal  for  oxygen. 

This  may  be  seen  by  pouring  some  strong  nitric  acid  on  iron  filings, 
or  powdered  tin.  The  acid  must  be  of  greater  density  than  1.48, 
otherwise  it  will  not  produce  the  effect.  Violent  heat,  attended  with 
red  fumes,  will  be  produced,  and  the  metals  will  be  oxidized. 

When  oxidation  is  effected  through  the  medium  of  nitric  acid,  the 
acid  itself  is  commonly  converted  into  binoxide  of  nitrogen.  This 
gas  is  sometimes  given  oflf  nearly  quite  pure  ; but  in  general  some 
nitrous  acid,  protoxide  of  nitrogen,  or  pure  nitrogen,  is  disengaged 
at  the  same  time. 

483.  Nitric  acid  maybe  decomposed  by  passing  its  vapour  through 
a red  hot  porcelain  tube  ; oxygen  is  given  off,  nitrous  acid  gas  is 
produced,  and  a quantity  of  diluted  acid  passes  over  into  the  receiver, 
having  escaped  decomposition  ; so  that  it  is  thus  proved  to  consist  of 
nitrous  acid  gas,  oxygen  and  water. 

For  experiments  of  this  kind  the  form  of  apparatus,  described  for 
the  decomposition  of  water  by  iron  (405),  may  be  employed,  omitting 
the  condensing  worm-pipq,  and  substituting  a porcelain  tube. 

484.  All  the  salts  of  nitric  acid  are  soluble  in  water,  and,  there- 


*See  Hare’s  Compend , 171. 


Carbon — Diamond . 


151 


fore,  it  is  impossible  to  precipitate  that  acid  by  any  re-agent.  The  Sect,  iv. 
presence  of  nitric  acid,  when  uncombined,  is  readily  detected  by  its 
strong  action  on  copper  and  mercury,  emitting  ruddy  fumes  of  nitrous 
acid,  and  by  its  forming  with  potassa  a neutral  salt,  which  crystallizes 
in  prisms,  and  has  all  the  properties  of  nitre.  Gold-leaf  is  a still  more  Tests  of, 
delicate  test.  When  hydrochloric  acid  is  added  to  the  solution  of  a 
nitrate,  chlorine  is  disengaged,  and  the  liquid  hence  acquires  the 
property  of  dissolving  gold-leaf ; but  as  the  action  of  hydrochloric 
acid  on  the  salts  of  Chloric,  bromic,  iodic,  and  selenic  acids  likewise 
yields  a solution  capable  of  dissolving  gold,  no  inference  can  be  drawn 
from  the  experiment,  unless  the  absence  of  these  acids  shall  have 
been  previously  demonstrated.  A very  delicate  test  has  been  pro- 
posed by  O’Shaugnessy,  founded  on  the  orange-red  followed  by  a 
yellow  colour,  which  nitric  acid  communicates  to  morphia.  The 
supposed  nitrate  is  heated  in  a test  tube  with  a drop  of  sulphuric 
acid,  and  then  a crystal  of  morphia  is  added. ^ It  is  advisable  to  try 
the  process  in  a separate  tube  with  the  sulphuric  acid  alone,  in  order 
to  prove  the  absence  of  nitric  acid.  T. 

485.  Nitric  acid  is  of  considerable  use  in  the  arts.  It  is  employed  Uses* 
for  etching  on  copper,  as  a solvent  of  tin  to  form  with  that  metal  a 
mordant  for  some  of  the  finest  dyes  ; in  metallurgy  and  assaying  ; 

in  various  chemical  processes,  on  account  of  the  facility  with  which 
it  parts  with  oxygen  and  dissolves  metals;  in  medicine  as  a tonic, 

&c.  For  the  purposes  of  the  arts  it  is  commonly  used  in  a diluted  . 
state,  and  contaminated  with  the  sulphuric  and  hydrochloric  acids,  by  fortis. 
the  name  of  aquafortist 

Section  IV.  Carbon . 

Symb.  Sp.  Gr.  ( hypothetical .)  Chem.  Equiv. 

C.  0.4215  air  =1  By  Vol.  100 

6.12  Hyd.=l  “ Wght.  6.12 

486.  The  purest  form  of  carbon  is  the  diamond ; from  its  powers  Purest 
of  refracting  light,  Newton  inferred  that  it  was  a combustible  body.  form’ 
The  diamond  is  the  hardest  substance  in  nature.  Its  texture  is 
crystalline  in  a high  degree,  and  its  cleavage  very  perfect.  Its  pri- 
mary form  is  the  octohedron.  Its  specific  gravity  is  3.52.  Acids- 

and  alkalies  do  not  act  upon  it;  and  it  bears  the  most  intense  heat 
in  close  vessels  without  fusing  or  undergoing  any  perceptible 
change.  Heated  to  redness  in  the  open  air,  it  is  entirely  consumed. 
Lavoisier  first  proved  it  to  contain  carbon  by  throwing  the  sun’s 
rays,  concentrated  by  a powerful  lens,  upon  a diamond  contained  in 
a vessel  of  oxygen  gas.  The  diamond  w&s  consumed  entirely,  oxy- 
gen disappeared,  and  carbonic  acid  was  generated.  It  has  since 
been  demonstrated  by  the  researches  of  others,  that  carbonic  acid  is 
the  product  of  its  combustion.! 

* Lancet,  1829—30. 

+ This  is  often  prepared  by  mixing  common  nitre  with  an  equal  weight  of  sulphate 
of  iron,  and  half  its  weight  of  the  same  sulphate  calcined,  and  distilling  the  mixture; 
or  by  mixing  nitre  with  twice  its  weight  of  dry  powdered  clay,  and  distilling  in  a 
reverberatory  furnace.  Two  kinds  are  found  in  the  shops,  one  called  double  aqua- for- 
tis, which  is  about  half  the  strength  of  nitric’acid ; the  other  simply  aqua-forlis,  which 
is  half  the  strength  of  the  double. 

t For  a description  and  plates  of  the  various  forms  of  apparatus  contrived  for  the 
combustion  of  the  diamond,  see  Henry’s  and  Brande’s  vols.  i. ; also  1st  and  2d 
editions  of  this  Manual . 


152 


Carbon. 


Chap.  III. 


Charcoal. 


Method  of 

preparing 

charcoal. 


Lamp- 

black. 


Animal 

charcoal. 


Its  proper- 
ties. 


Combus- 
tion in  ox- 
ygen. 


Absorbing 

power. 


487.  Guyton-Morveau  inferred  from  his  experiments  that  the  dia- 
mond is  pure  carbon,  and  that  charcoal  is  an  oxide  of  carbon.  Ten- 
nant burned  diamonds  by  heating  them  with  nitre  in  a gold  tube; 
and  comparing  his  own  results  with  those  of  Lavoisier  on  the  com- 
bustion of  charcoal,  he  concluded  that  equal  weights  of  diamond  and 
pure  charcoal,  in  combining  with  oxygen,  yield  precisely  equal 
quantities  of  carbonic  acid.  He  was  thus  induced  to  adopt  the  opin- 
ion, that  charcoal  and  the  diamond  are  chemically  the  same  sub- 
stance ; and  that  the  difference  in  their  physical  character  is  solely 
dependent  on  a difference  of  aggregation.*  This  conclusion  was 
confirmed  by  the  experiments  of  Allen  and  Pepys,t  and  Davy.t  § 

Another  form  of  carbon  is  charcoal,  the  purest  variety  of  which  is 
lamp-black.  II 

488.  Charcoal  may  be  prepared  by  heating  pieces  of  wood,  cover- 
ed with  sand,  to  redness,  and  keeping  them  in  that  state  for  about 
an  hour.  They  are  converted  into  a black  brittle  substance,  which 
appears  to  be  the  same  from  whatever  kind  of  wood  it  has  been  pro- 
cured. 

Lamp-black  is  prepared  from  refuse  and  residuary  resin.  When 
lamp-black  has  been  heated  red-hot  in  a close  vessel,  it  may  be  con- 
sidered as  very  pure  carbon.  A very  pure  charcoal  is  obtained 
from  spirits  of  wine. 

Animal  charcoal,  or  ivory  black , is  a mixture  of  charcoal  and  phos- 
phate of  lime,  prepared  by  exposing  bones  to  heat  in  a close  vessel. 
The  quantity  of  charcoal  obtained  from  different  kinds  of  wood  is 
liable  to  much  variation. 

489.  Charcoal  is  black,  insoluble,  inodorous,  insipid,  and  brittle  ; 
an  excellent  conductor  of  electricity,  but  a bad  conductor  of  heat ; un- 
changed by  the  combined  action  of  air  and  moisture  at  common  tem- 
peratures ; and  easily  combustible  inroxygen  gas.  The  combustion  of 
charcoal  in  oxygen  has  been  already  noticed.  (367)  The  product  of 
the  combustion  is  carbonic  acid  gas,  the  oxygen  neither  increasing 
nor  diminishing  in  volume,  but  becoming  heavier  by  the  quantity  of 
carbon  which  combines  with  it ; every  sixteen  parts  of  oxygen  take 
up  six  of  carbon. 

490.  Charcoal  likewise  absorbs  the  odoriferous  and  colouringprin- 
ciples  of  most  animal  and  vegetable  substances.  When  coloured 
infusions  of  this  kind  are  digested  with  a due  quantity  of  charcoal,  a 
solution  is  obtained,  which  is  nearly  if  not  quite  colourless.  Tainted 
flesh  may  be  deprived  of  its  odour  by  this  means,  and  foul  water  be 
purified  by  filtration  through  charcoal.  The  substance  commonly 
employed  to  decolorize  fluids  is  animal  charcoal  reduced  to  a fine 
powder.  It  loses  the  property  of  absorbing  colouring  matters  by  use, 
but  recovers  it  by  being  heated  to  redness. 


* Phil.  Trans,  for  1797.  Ibid,  1807.  i Ibid,  1814. 

§ The  latter  chemist  did  indeed  observe  the  production  of  a minute  quantity  of  water 
during  the  combustion  of  the  purest  charcoal,  indicative  of  a trace  of  hydrogen;  but 
its  quantity  is  so  small,  that  it  cannot  he  regarded  as  a necessary  constituent.  It 
proves  only  that  a trace  of  hydrogen  is  retained  by  charcoal  with  such  force,  that  it 
cannot  be  expelled  by  the  temperature  of  ignition.  T. 

||  Graphite , or,  as  commonly  called  black  lead , is  a natural  compound  of  carbon  and 
iron  ; some  varieties  appear  to  he  a peculiar  form  of  carbon,  leaving  very  little  residu- 
um when  burned.  Anthracite  is  another  variety. 


Carbonic  Acid. 


153 


491.  The  charcoal  of  wood,  besides  its  use  as  a fuel,  is  necessary  Sect,  iv. 
to  the  preparation  of  that  kind  of  iron  which  is  used  for  wire ; to  the  Use  in  the 
cementation  of  steel;  and  to  the  preparation  of  gunpowder.  Fromarts* 

the  powerful  affinity  which  it  has  for  oxygen  at  a high  temperature, 
it  is  constantly  employed  for  deoxidating  the  metals  and  many  other 
substances. 

The  charcoal  prepared  from  pit-coal,  called  coke,  is  less  pure,  and,  Coke, 
besides  other  substances,  generally  contains  sulphur,  but  it  has  the 
advantage  of  being  heavier  and  more  compact,  in  consequence  of 
which  it  is  better  adapted  for  burning  in  furnaces  in  which  there  is  a 
powerful  blast  of  air.  H.  i.  330. 

492.  When  large  quantities  of  charcoal,  in  a state  of  minute  divi-  Spontane- 
sion,  are  left  undisturbed,  spontaneous  combustion  generally  ensues, 

and  occasionally  with  charcoal  in  fragments  of  considerable  size,  charcoal. 
This  has  been  attributed  to  the  action  of  air  and  moisture  on  minute 
quantities  of  potassium  present  in  the  coal.^ 

493.  The  hypothetical  density  of  the  vapour  of  carbon,  calculated  Density, 
as  explained  at  page  33,  is  0.4215,  and  100  cubic  inches  of  it  should 
weigh  13.0714  grains. 

Carbon  and  Oxygen. 

494.  There  are  two  compounds  of  carbon  and  oxygen ; carbonic 

oxide  and  carbonic  acid  gases.  Carbonic  oxide  gas  is  theoretically  Compounds 
considered  as  a compound  of  100  measures  of  the  vapour  of  carbon  ^a^on 
and  50  of  oxygen  condensed  into  100  measures  ; and  carbonic  acid  gen.°xy 
gas,  of  100  measures  of  the  vapour  of  carbon  and  100  of  oxygen 
condensed  into  100  measures. 

The  composition  of  these  compounds  of  carbon  is  as  follows 

Carbon.  Oxygen.  Equiv.  Formula. 

Carbonic  oxide  6,12  or  1 eq.  -f-  8 or  1 eq.  = 14.12  C-f-O  or  C. 

Carbonic  acid  6.12  or  1 eq.  -f-  16  or  2 eq.  = 22.12  C-f-20  or  C. 

Carbonic  Acid. 

495.  Carbonic  acid  was  discovered  by  Black  in  1757,  and 
scribed  by  him  under  the  name  of  fixed  air.  He  observed  the  exist-  aem" 
ence  of  this  gas  in  common  limestone  and  magnesia,  and  found  that 

it  may  be  expelled  from  these  substances  by  the  action  of  heat.  It 
may  be  obtained  by  burning  carbon,  either  pure  charcoal  or  the  dia- 
mond, in  oxygen  gas.  The  best  mode  of  procuring  it  for  experiment 
consists  in  acting  upon  marble  [carbonate  of  lime)  by  dilute  hydro-  Processes, 
chloric  acid.  The  hydrochloric  acid  takes  the  lime,  and  carbonic 
acid  gas  escapes  with  effervescence. 

For  this  purpose  the  marble,  in  fragments,  is  placed  in  the  gas  bottle  (Fig.  85 
or  86)  and  hydrochloric  acid,  previously  diluted  with  water,  poured  upon  it : im- 


* See  Aubert’s  .paper  on  this  subject  in  Phil.  Mag.  and  Ann.  N.  S.,  Vol.  ix. 
148,  and  Hadfield’s  and  Davies’s  papers  in  Lond.  and  Edin.  Phil.  Mag.  iii. 

20 


Composi- 

tion, 


de-  Carbonic 


154 


Carbon  and  Oxygen. 


W 


a 


145, 


Chap.  Iir.  mediate  effervescence  ensues,  and  the  gas.is  Fig.  144. 

conveyed  by  the  bent  pipe  to  an  inverted  jar 
on  the  shelf  of  the  pneumatic  trough,  (Figs, 

96,  97.)  When  the  action  ceases,  it  may  be 
renewed  by  the  addition  of  fresh  acid  until 
the  marble  is  dissolved. 

Or  the  apparatus,  (Fig.  144,)  may  be  em- 
ployed, the  acid  being  poured  down  the  tube 
0,  which  passes  to  the  bottom  of  the  two 
necked  bottle,  a. 

As  carbonic  acid  gas  is  heavier  than  at- 
mospheric air  it  may  also  be  obtained  by 
means  of  the  apparatus,  (Fig.  145)  ; a is  a long 
glass  tube  proceeding  from  the  bottle  contain- 
ing the  marble  and  acid,  and  passing  down  to  the  bottom  of 
the  jar  b,  which  stands  with  its  mouth  uppermost.  The  car- 
bonic acid  will  expel  the  common  air  from  the  jar. 

Properties.  496.  Carbonic  acid,  as  thus  procured,  is  a colour- 
less, inodorous,  elastic  fluid,  which  possesses  all 
the  physical  characters  of  the  gases  in  an  eminent 
degree,  and  requires  a pressure  of  thirtysix  atmos- 
pheres to  condense  it  into  a liquid.  The  exact  know- 
ledge of  its  density  is  still  an  important  desidera- 
tum: it  is  estimated  at  1.524  by  Dulong  and 
Berzelius,  and  at  1.5277  by  Thomson.*  If  its  specific  gravity  is  es- 
timated as  1.5239,  100  cubic  inches  should  weigh  47.2586  grs.  T. 

497.  Carbonic  acid  may  be  collected  over  water,  but  must  be  pre- 
served in  vessels  with  glass-stoppers,  since  water,  at  common  tempe- 
rature and  pressure,  takes  up  its  own  volume. 

Fill  partly  a jar  with  this  gas,  and  let  it  stand  a few  hours  over  water.  An 
absorption  will  gradually  go  on,  till  at  last  none  will  remain.  This  absorption  is 
infinitely  quicker  when  agitation  is  used.  Repeat  the  above  experiment,  with 
this  difference,  that  the  jar  must  be  shaken  strongly.  A very  rapid  diminution 
will  now  take  place.  In  this  manner,  water  may  be  charged  with  rather  more 
than  its  own  bulk  of  carbonic  acid  gas  ; and  it  acquires,  when  thus  saturated,  a 
brisk  and  pleasant  taste. 

Water  im-  498.  The  effervescent  quality,  and  brisk,  pungent  taste  of  ferment- 
pregnated.  e(j  liquors  is  due  to  the  presence  of  this  gas,  as  is  likewise  that  of 
many  mineral  waters.  The  latter  are  often  imitated  by  condensing 
carbonic  acid  into  water,  either  by  a condensing  pump,  of  which  a 
description  is  given  by  Pepy’s,!  or  by  a Nooth’s  apparatus,  as  repre- 
sented in  Fig.  1464 


Absorbed 
by  water. 


Exp. 


Nooth’s  appa- 
ratus. 


* First  Principles , i.  143. 

+ Quar.  Jour,  of  Sci.  and  the  Arts,  vol.  iv.  p.  305. 
t It  consists  of  three  vessels,  the  lowest,  a,  flat  and  broad,  so 
as  to  form  a steady  support : it  contains  the  materials  for  evolv- 
ing the  gas,  such  as  pieces  of  marble  and  dilute  hydrochloric 
acid,  of  which  fresh  supplies  may  occasionally  be  introduced  through 
the  stopped  aperture.  The  gas  passes  through  the  tube  b,  in 
which  is  a glass  valve  opening  upwards,  into  the  vessel  c,  contain- 
ing the  water  or  solution  intended  to  be  saturated  with  the  gas, 
and  which  may  occasionally  be  drawn  off  by  the  glass  stop-cock. 
Into  this  dips  the  tube  of  the  uppermost  vessel  d,  which  occa- 
sions some  pressure  on  the  gas  in  c,  and  also  produces  a circulation 
and  agitation  of  the  water.  At  the  top  of  d is  a conical  siopper, 
which  acts  as  an  occasional  valve,  and  keeps  up  a degree  of  pressure 
in  the  vessels. 


Fig.  146. 


155 


Carbonic  Acid— properties  of. 


The  escape  of  carbonic  acid  from  fermented  liquors 
may  be  shown  by  placing  three  or  four  ounces  of  ale  or 
porter  in  a jar  or  tube,  (Fig.  147)  twenty  or  more  inches 
in  height,  on  the  plate  of  the  air-pump,  covering  it  with 
a tall  receiver,  and  exhausting  the  air.  The  foam  will 
rise  and  entirely  fill  the  jar  or  tube. 

Under  a pressure  of  two  atmospheres  water 
dissolves  twice  its  volume  of  this  gas,  and  so 
on.  It  thus  becomes  brisk  and  tart,  and  red- 
dens delicate  vegetable  blues.  By  freezing, 
boiling,  or  exposure  to  the  vacuum  of  the  air- 
pump,  the  gas  is  given  off. 

Place  a tumbler  of  water  which  has  been  impregnated 
with  this  gas  (the  soda-water  of  the  shops  for  example) 
under  the  receiver  of  the  air-pump,  and  exhaust  it ; the 

gas  will  escape  so  rapidly  as  to  present  the  appearance  , 

of  ebullition  ; and  will  be  much  more  remarkable  than  “ pi*  ~ “ 

the  discharge  of  air  from  another  vessel  of  common 
spring  water,  confined  at  the  same  time  under  the  receiver. 

499.  If  the  impregnated  water  be  rapidly  congealed,  by  surround-  Expelled 
ing  it  with  a mixture  of  snow  and  salt,  the  frozen  water  has  more  by  freezing, 
the  appearance  of  snow  than  of  ice,  its  bulk  being  prodigiously  in- 
creased by  the  immense  number  of  air  bubbles.  When  water,  thus 
congealed,  is  liquefied  again,  it  is  found,  by  its  taste,  and  other  pro- 
perties, to  have  lost  nearly  the  whole  of  its  carbonic  acid. 

500.  Carbonic  acid  extinguishes  burning  substances  of  all  kinds, Does  not 
and  the  combustion  does  not  cease  from  the  want  of  oxygen  only.  ItcoSbus- 
exerts  a positive  influence  in  checking  combustion,  as  appears  fromtion. 
the  fact  that  a candle  cannot  burn  in  a gaseous  mixture  composed  of 

four  measures  of  atmospheric  air  and  one  of  carbonic  acid. 

This  may  be  shown  by  setting  a vessel  filled  with  the  gas,  with  the  mouth  up-  Exp. 
wards,  and  letting  down  a lighted  candle. 

The  experiment  may  be  varied  by  placing  near  the  vessel  containing  the 
carbonic  acid  gas,  a similar  one  filled  with  oxygen  gas,  and  if  the  candle,  after 
being  extinguished  by  the  carbonic  acid  be  speedily  immersed  in  the  oxygen  gas 
it  will  be  relighted,  and  this  may  be  repeated  as  long  as  the  gases  remain  in  the 
vessels. 

501.  It  is  not  better  qualified  to  support  the  respiration  of  animals  ;Fata!j» 
for  its  presence,  even  in  moderate  proportion,  is  soon  fatal.*  An  ani-ammas“ 
mal  cannot  live  in  air  which  contains  sufficient  carbonic  acid  for  ex- 
tinguishing a lighted  candle  ; and  hence  the  practical  rule  of  letting 
down  a burning  taper  into  old  wells  or  pits  before  any  one  ventures 

to  descend.  If  the  light  is  extinguished,  the  air  is  certainly  impure; 
and  there  is  generally  thought  to  be  no  danger  if  the  candle  conti- 
nues to  burn.  But  instances  have  been  known  of  the  atmosphere 
being  sufficiently  loaded  with  carbonic  acid  to  produce  insensibility, 
and  yet  not  so  impure  as  to  extinguish  a burning  candle. t When 
an  attempt  is  made  to  inspire  pure  carbonic  acid,  violent  spasm  of 


* By  means  of  this  gas,  butterflies,  and  other  insects,  the  colours  of  which  it  is  de- 
sirable to  preserve,  for  the  purpose  of  cabinet  specimens,  may  be  suffocated  better  than 
by  the  common  mode  of  killing  them  by  the  fumes  of  sulphur.  H. 
t Christison  on  Poisons,  2d  ed.  707. 

Two  instances  recently  occurred  at  Cambridge,  where  a candle  continued  burning 
sn  an  apartment  in  which  two  men  were  found  insensible,  one  was  with  great  diffi- 
culty recovered,  the  other  died.  W. 


Fig.  147.  Sect.  IV. 


Exp. 


1 

§ 

£2) 


Exp. 


156 


Chap.  III. 


Heavier 
than  atmos 
pheric  air. 
Exp. 


Possesses 
acid  pro- 
perties. 


Carbon  and  Oxygen. 

. the  glottis  takes  place,  which  prevents  the  gas  from  entering  the 
lungs.  If  it  be  so  much  diluted  with  air  as  to  admit  of  its  passing 
the  glottis,  it  then  acts  as  a narcotic  poison  on  the  system.  It  is  this 
gas  which  has  often  proved  destructive  to  persons  sleeping  in  a con- 
fined room  with  a pan  of  burning  charcoal. 

502.  Carbonic  acid  gas  is  heavier  than  atmospheric  air,  and  may 
be  poured  from  one  vessel  into  another  like  water. 

Place  a lighted  taper  at  the  bottom  of  a tall  glass  jar,  and  pour  the  gas  out  of  a 
bottle  into  it;  it  descends  and  extinguishes  the  flame,  and  will  remain  a long 
time  in  the  lower  part  of  the  jar. 

Hence  in  wells  and  in  some  caverns,  carbonic  acid  gas  frequently 
occupies  the  lower  parts,  while  the  upper  parts  are  free  from  it.  The 
miners  call  it  choaJc  damp. 

503.  When  combined  with  water  this  gas  reddens  vegetable  co- 
lours. This  may  be  shown  by  dipping  into  water,  thus  impregnated, 
a bit  of  litmus  paper,  or  by  mixing,  with  a portion  of  it,  about  an 
equal  bulk  of  the  infusion  of  litmus.  This  establishes  the  title  of  the 
gas  to  be  ranked  among  acids.  When  an  infusion  of  litmus  which  has 
been  thus  reddened,  is  either  heated,  or  exposed  to  the  air,  its  blue 
colour  is  restored,  in  consequence  of  the  escape  of  the  carbonic  acid. 
This  is  a marked  ground  of  distinction  from  most  other  acids,  the 
effect  of  which  is  permanent,  even  after  boiling. 

504.  Carbonic  acid  gas  precipitates  lime-water — this  character  of 
the  gas  affords  a ready  test  of  its  presence,  whenever  it  is  suspected. 

Pass  the  gas  as  it  proceeds  from  the  materials,  through  a portion  of  lime-water. 
This,  though  perfectly  transparent  before,  will  grow  milky  : Or,  mix  equal  mea- 
sures of  water  saturated  with  carbonic  acid,  and  lime-water. 

By  means  of  lime-water,  the  whole  of  any  quantity  of  carbonic 
acid,  existing  in  a mixture  of  gases,  cannot,  however,  be  removed,  but 
recourse  must  be  had,  in  order  to  effect  an  entire  absorption,  to  a so- 
lution of  caustic  potassa  or  soda.^ 

505.  As  all  common  combustibles,  such  as  coal,  wood,  oil,  wax, 
tallow,  &c.  contain  carbon  as  one  of  their  component  parts,  so 
the  combustion  of  these  bodies  is  always  attended  by  the  production 
of  carbonic  acid. 

1.  Let  the  chimney  of  a portable  furnace,  in  which  charcoal  is  burning  ter- 
minate, at  a distance  sufficiently  remote  to  allow  of  its  being  kept  cool,  in  the 
bottom  of  a barrel,  provided  with  a moveable  top,  or  of  a large  glass  vessel,  having 
two  openings.  A small  jar  of  lime-water  being  let  down  into  the  tube  or  vessel, 
and  agitated,  the  lime-water  will  immediately  become  milky.  The  gas  will  also 
extinguish  burning  bodies,  and  prove  fatal  to  animals  that  are  confined  in  it. 

2.  Fill  the  pneumatic  trough  with  lime-water,  and  burn  a candle,  in  a jar 
filled  with  atmospheric  air,  over  the  lime-water  till  the  flame  is  extinguished. 
On  agitating  the  jar,  the  lime-water  will  become  milky.  The  same  appearances 
will  take  place,  more  speedily  and  remarkably  if  oxygen  gas  be  substituted  for 
common  air.  H.  1.351. 

And  of  res-  506.  It  is  also  produced  by  the  respiration  of  animals  ; hence  it  is 
piration.  detected  often  in  considerable  proportion,  in  crowded  and  illuminated 
rooms,  which  are  ill-ventilated,  and  occasions  difficulty  of  breathing, 
giddiness,  and  faintness. 


Test  of  its 
presence. 

Exp. 


A product 
of  combus- 
tion, 


Exp. 


Exp. 


* If  excess,  either  of  the  gas  or  of  its  aqueous  solution,  be  added  to  the  lime-water, 
the  precipitate  is  re-dissolved,  carbonate  of  lime  being  soluble  in  carbonic  acid. 


Carbonic  Acid — solidified . 157 

The  production  of  carbonic  acid,  by  respiration,  may  be  proved  by  Sect,  iv. 
blowing  the  air  from  the  lungs,  with  the  aid  of  a quill,  through  lime- 
water,  which  will  become  milky. 

507.  Carbonic  acid  retards  the  putrefaction  of  animal  substances.  Retards  pu- 

It  exerts  powerful  effects  on  living  vegetables.  These  effects,  j^fefocts' 

however,  vary  according  to  the  mode  of  its  application.  Water  sa-onvegeta_ 
turated  with  this  gas,  proves  highly  nutritive  when  applied  to  the  bles. 
roots  of  plants.  The  carbonic  acid  is  decomposed,  its  carbon  form- 
ing a component  part  of  the  vegetable,  and  its  oxygen  being  liberated 
in  a gaseous  form. 

On  the  contrary,  carbonic  acid,  when  a living  vegetable,  is  con- 
fined in  the  undiluted  gas  over  water,  is  injurious  to  the  health  of 
the  plant,  especially  in  the  shade. 

It  is  this  process  of  nature  that  appears  to  be  the  principal  means 
of  preventing  an  excess  of  carbonic  acid  in  the  general  mass  of  the 
atmosphere,  which,  without  some  provision  of  this  kind,  must  gradu- 
ally, in  the  course  of  ages,  be  rendered  less  and  less  fit  for  respira- 
tion. 

508.  Carbonic  acid  was  first  obtained  in  a liquid  form  by  Faraday,  Liquefac- 
from  carbonate  of  ammonia  and  sulphuric  acid.  Very  strong  tubes  carbonic 
are  required,  and  even  those  which  have  held  fluid  carbonic  acid  for  acid, 
many  days,  have,  upon  a slight  elevation  of  temperature,  spontane- 
ously exploded  with  great  violence.  Great  care  is  necessary,  and 

the  protection  of  a glass  mask,  goggles,  &c.,  in  repeating  the  pro- 
cess with  glass  tubes.  The  liquid  acid  is  a limpid,  colourless  body, 
extremely  fluid,  distilling  readily  at  the  difference  of  temperature 
between  32°  and  0°.  Its  refractive  power  is  much  less  than  that  of 
water.  Its  vapour  exerts  a pressure  of  thirtysix  atmospheres  at  a 
temperature  of  32°.^ 

A safer  method  of  obtaining  the  liquid  acid  as  contrived  by  Thil-  Solidifica- 
lorier,  is  with  the  aid  of  a strong  metallic  apparatus  in  which  it  may  tioa  of* 
be  condensed  mechanically.  When  allowed  to  escape  from  a stop- 
cock attached  to  the  receiver,  the  liquid  gas  expands  with  so  much 
rapidity  that  great  absorption  of  caloric  attends,  and  a part  of  the  gas 
is  rendered  solid,  resembling  snow.  A reduction  of  temperature  to 
— 162°  is  said  to  have  been  obtained  by  this  means ; hence  mercury 
can  be  readily  frozen  by  it.f 


* Faraday,  Phil.  Trans. 

t See  Lond.  and  Edin.  Phil.  Mag.  x.  158. 

The  experiments  of  Thillorier  have  been  repeated  by  Mitchell  of  Philadelphia,  by 
means  of  an  apparatus  consisting  of  two  strong  vessels  of  cast  iron.  The  two  vessels 
can  be  firmly  attached,  a stop-cock  being  interposed.  The,  gas  is  generated  in  the 
larger  vessel.  The  materials  employed,  are  Ulbs.  of  bicarbonate  of  soda,  24  ounces 
of  water,  and  9 ounces  of  sulphuric  acid  ; the  latter,  being  placed  in  a smaller  vessel 
which  is  enclosed  in  the  cylinder,  is  not  allowed  to  come  in  contact  with  the  bicarbo- 
nate of  soda  until  the  aperture  by  which  it  is  introduced  has  been  firmly  secured,  when 
the  cylinder  is  brought  to  a horizontal  position  and  the  liquids  are  mingled.  The  re- 
ceiver, previously  cooled  by  ice,  is  now  attached,  and  the  liquid  carbonic  acid  allowed 
to  pass  into  it,  from  which  it  may  be  permitted  to  escape  as  wanted. 

The  pressure  at  32°  was  found  by  Mitchell  to  be  36  atmospheres,  at  66°,  60  atmos- 
pheres, and  at  86°,  72  atmospheres.  The  condensed  acid  obtained  by  Mitchell,  when 
recently  formed  was  about  the  weight  of  carbonate  of  magnesia,  perfectly  white,  and 
of  a soft  and  spongy  texture.  It  evaporates  rapidly,  becoming  colder,  and  the  mass  may 
be  kept  for  some  time.  A quantity  weighing  346  grains  lost  from  three  to  four  grains 
per  minute  at  first,  but  did  not  entirely  disappear  for  three  hours  and  a half.  The  na- 


158 


Carbon  and  Oxygen. 

Chap,  hi.  509.  Carbonic  acid  combines  with  bases,  and  the  compounds  are 
Carbon-  termed  carbonates  : as  it  is  usually  retained  in  combination  by  very 
ates.  feeble  affinity,  so  it  is  evolved  from  most  of  the  carbonates  by  the 
simple  operation  of  heat.  Thus  chalk,  when  heated,  gives  out  car- 
Efferves-  bonic  acid,  and  becomes  quicklime.  It  is  also  evolved  from  its  com- 
cence.  binations  by  most  of  the  other  acids,  with  effervescence. 

ascertain °f  The  quantity  of  carbonates  in  any  saline  mass,  may  be  as- 

ingquanti-  certained  by  noting  the  quantity  of  carbonic  acid  disengaged.  This 

ties  of  car-  may  be  done  by  measuring  the  volume  of  gas,  or  by  ascertaining  its 
bonic  acid.  wefght>  y * 

In  the  first  case,  the  easiest  method  of  proceeding  is  to  fill  a long  tube  (closed 
at  one  end,  and  capable  of  containing  two  or  three  cubic  inches),  nearly  full  of 
mercury,  filling  it  completely  afterwards  with  hydrochloric  acid  diluted  with  an 
equal  quantity  of  water.  The  thumb  is  placed  over  this,  after  dipping  it  in  oil, 
or  rubbing  it  over  with  a little  gas  lute,*  the  tube  inverted,  and  placed  in  a cup 
of  mercury.  One  or  two  grains  of  the  solid  salt  are  then  introduced  into  the  tube, 
(the  experiment  is  most  easily  performed  with  a fragment  of  some  carbonate,) 
and  the  moment  it  rises  to  the  top,  and  comes  in  contact  with  the  acid,  the  car- 
bonic acid  is  disengaged  with  effervescence,  depressing  the  mercury,  and  its 
amount  is  estimated  by  examining  the  volume  which  it  occupies  and  making  the 
usual  corrections ; one  equivalent  of  carbonic  acid  indicating  one  equivalent  of  a 
carbonate,  whatever  may  be  the  nature  ot  the  base. 

In  the  other  method,  a thin  glass  flask  or  bottle,  of  the  form  shown  in  Fig.  148, 
is  placed  on  one  of  the  scales  of  a balance  with  some  hydrochloric  acid,  big.  148. 
and  accurately  counterpoised  along  with  a given  weight  of  the  sub- 
stance under  examination,  and  the  bent  tube  passing  through  a cork, 
which  fits  to  the  mouth  of  the  flask.  This  tube  is  put  in  when  the  acid 
and  carbonates  are  mixed  together,  to  prevent  any  loss  from  particles  of 
liquid  that  may  be  thrown  up  during  the  effervescence,  and  it  is  evident 
that,  by  adding  weights  to  the  scale  on  which  the  glass  vessel  is  placed 
(when  the  effervescence  has  finished),  till  it  is  again  counterpoised, 
they  will  indicate  the  quantity  of  carbonic  acid  that  has  been  evolved  ; before 
weighing  it  the  second  time,  the  cork  and  tube  should  be  taken  out  till  the  car- 
bonic acid  gas  in  the  interior  has  been  blown  out  gently  by  a pair  of  bellows. t 

A convenient  mode  is  by  means  of  an  alltalimeter.  Into  a tube  sealed  at 
one  end,  9£  inches  long,  |ths  of  an  inch  in  diameter,  and  as  cylindrical  as  possi- 
Alkalime-  ble  in  its  whole  length,  pour  1000  grains  of  water,  and  with  a file  or  diamond,  mark 
ter.  the  place  where  its  surface  reaches,  divide  the  space  occupied  by  the  water  into 


tural  temperature  was  76°— 79°.  The  temperature  of  the  mass  continued  to  decrease, 
which  was  accelerated  by  any  means  for  increasing  the  evaporation.  At  its  formation 
the  carbonic  snow  depressed  the  thermometer  to  about— 85.  The  greatest  cold  pro- 
duced hy  the  solid  acid  in  the  air  was — 109°,  under  an  exhausted  receiver — 136°. 

Mercury  placed  in  a cavity  in  it  and  covered  up  with  the  same  substance,  was 
frozen  in  a few  seconds.  At  about — 110°  liquid  sulphurous  acid  was  frozen,  and  at 
— 130°  alcohol  of  .793  assumed  a viscid  and  oily  consistence,  and  at — 146°  was  like 
melted  wax.  Alcohol  of  .820  froze  readily.  A piece  of  solid  carbonic  acid  applied 
to  the  skin  produced  a ghastly  white  spot,  and  in  fifteen  seconds  raised  a blister. 

Its  specific  gravity  at  32°  F.  was  .93,  at  43°  5,  .8325.  Liquid  carbonic  acid  did  not 
appear  to  act  upon  any  of  the  metals  or  oxides.  When  the  liquid  acid  has  been  frozen 
in  a tube  of  glass,  the  lube  may  be  melted  off  and  hermetically  sealed.  Such  a tube 
will  always  retain  the  liquid,  or  gas;  the  former,  if  in  sufficient  quantity,  at  all  tem- 
peratures, if  not,  th,e  latter  alone  will  be  found  in  it  at  high  temperatures.  In  such  a 
tube  moisture  appears  at  56°,  and  a constantly  elongating  cylinder  of  liquid  forms  as 
the  coldness  increases:  at  32°  the  cylinder  is  about  half  an  inch  in  length.  See 
Mitchell’s  paper  and  plate  in  the  Jour,  of  Franklin  Institute , vol.  xxii,  and  Amer. 
Jour.  xxxv.  346. 

* This  is  a very  convenient  lute  for  rendering  joints  in  apparatus  tight,  and  is  com- 
posed of  one  part  of  wax  and  three  of  lard  heated  together  until  of  uniform  consistence. 

t Reid. 


Carbonic  Oxide. 


159 


100  equal  parts,  as  shown  in  Fig.  140.  Opposite  to  the  numbers  23, 

44,  48,  96,  54,  63,  and  65  draw  a line,  and  at  the  first  write  soda, 
at  the  second  potassa,  at  the  third  carbonate  of  soda,  and  at  the  fourth 
carbonate  of  potassa.  Prepare  a dilute  acid  having  the  specific  gra- 
vity of  1.127  at  60°,  which  may  be  made  by  mixing  one  measure  of 
concentrated  sulphuric  acid  with  four  measures  of  distilled  water. 

This  is  the  standard  acid  to  be  used  in  all  the  experiments,  being  of  — 
such  strength  that  when  poured  into  the  tube  till  it  reaches  either  of 
the  four  marks  just  mentioned,  we  shall  obtain  the  exact  quantity 
necessary  for  neutralizing  100  grains  of  the  alkali  written  opposite  to 
it.  If,  when  the  acid  reaches  the  words  carb.  potassa , and  when,  _t 
consequently,  we  have  the  exact  quantity  which  will  neutralize  100  — 
grains  of  that  carbonate,  pure  water  be  added  until  it  reaches  0,  or 
the  beginning  of  the  scale,  each  division  of  this  mixture  will  neutral- 
ize one  grain  of  carbonate  of  potassa.  All  that  is  now  required,  in 
order  to  ascertain  the  quantity  of  real  carbonate  in  any  specimen  of 
pearlash,  is  to  dissolve  100  grains  of  the  sample  in  warm  water,  filter 
to  remove  all  the  insoluble  parts,  and  add  the  dilute  acid  in  succes- 
sive small  quantities,  until,  by  the  test  of  litmus  paper,  the  solution 
is  exactly  neutralized.  Each  division  of  the  mixture  indicates  a grain  of  pure 
carbonate.  It  is  convenient  in  conducting  this  process,  to  set  aside  a portion  of 
the  alkaline  liquid,  in  order  to  neutralize  the  acid,  in  case  it  should  at  first  be 
added  too  freely.* 

Carbonic  Oxide  A 

511.  Carbonic  Oxide , discovered  by  Priestley,  is  usually  obtained  Carbonic 
by  subjecting  carbonic  acid  to  the  action  of  substances  which  abstract  oxide’ 

a portion  of  its  oxygen.  Upon  this  principle,  carbonic  oxide  gas  is 
produced  by  heating  in  an  iron  retort  a mixture  of  chalk  and  char- 
coal ; or  of  equal  weights  of  chalk  and  iron  or  zinc  filings.  It  is 
also  obtained  by  the  distillation  of  the  white  oxide  of  zinc  with  one  Howob- 
eighth  of  its  weight  of  charcoal,  in  an  earthen  or  glass  retort ; from  tained> 
the  scales  which  fly  from  iron  in  forging,  mixed  with  a similar  pro- 
portion of  charcoal ; from  the  oxides  of  lead,  manganese,  or,  indeed, 
of  almost  every  imperfect  metal,  when  heated  in  contact  with  pow- 
dered charcoal.  It  may  also  be  obtained  from  the  substance  which 
remains  after  preparing  acetic  acid  from  acetate  of  copper.  But  the 
mixture  that  affords  it  most  pure,  is  equal  parts  of  carbonate  of  ba- 
ryta and  clean  iron  filings  ; these  should  be  introduced  into  a small 
earthen  retort,  so  as  nearly  to  fill  it,  and  exposed  to  a red  heat : the 
first  portion  of  gas  being  rejected  as  mixed  with  the  air  of  the  retort, 
it.  may  afterwards  be  collected  quite  pure. 

512.  A very  elegant  mode  of  preparing  carbonic  oxide  has  been  Dumas’s 
suggested  by  Dumas. t The  process  consists  in  mixing  binoxalate  process, 
of  potassa  with  five  or  six  times  its  height  of  concentrated  sulphuric 

acid,  and  heating  the  mixture  in  a retort  or  other  convenient  glass 
vessel.  Effervescence  soon  ensues,  owing  to  the  escape  of  gas,  con- 
sisting of  equal  measures  of  carbonic  acid  and  carbonic  oxide  gases  ; 
and  on  absorbing  the  former  by  an  alkaline  solution,  the  latter  is  left 
in  a state  of  perfect  purity.  To  comprehend  the  theory  of  the  pro- 
cess, it  is  necessary  to  premise,  that  oxalic  acid  is  a compound  of 
carbonic  acid  and  carbonic  oxide,  or  at  least  its  elements  are  in  the 
proportion  to  form  these  gases  ; and  that  it  cannot  exist  unless  in 
combination  with  water  or  some  other  substance.  Now  the  sulphu- 
ric acid  unites  both  with  the  potassa  and  water  of  the  binoxalate, 


Fig.  149. 
O 


Sect.  IV. 


Q 
5 
10 
15 
20 
25 
30 
35 
40 
45 
5 O 
55 
60 
65 
70 
75 
80 
85 
90 
95 
100 


* Faraday’s  Chem.  Manip. 
t Edin.  Jour,  of  Sci.  vi.  350. 


t For  Composition,  &,c.  see  (494.) 


160 


Chap  III. 


Properties. 


Explodes 
witn  oxy- 
gen. 


Density. 


Analysis. 


And  spongy 
platinum. 


Carbon  and  Oxygen. 

and  the  oxalic  acid  being  thus  set  free,  is  instantly  decomposed. 
Oxalic  acid  may  be  substituted  in  this  process  for  binoxalate  of 
potassa. 

It  may  also  be  obtained  by  transmitting  carbonic  acid  gas  over 
charcoal  ignited  in  a porcelain  tube.  The  acid  gas  combines  with 
an  additional  dose  of  charcoal,  loses  its  acid  properties,  and  is  con- 
verted into  carbonic  oxide. 

513.  Carbonic  oxide  gas  is  colourless  and  insipid.  It  does  not 
affect  the  blue  colour  of  vegetables  in  any  way  ; nor  does  it  combine, 
like  carbonic  acid,  with  lime  or  any  of  the  pure  alkalies.  It  is  very 
sparingly  dissolved  by  water.  Lime-water  does  not  absorb  it,  nor  is 
its  transparency  affected  by  it. 

514.  The  nature  of  this  gas  was  first  made  known  by  Cruickshank, 
of  Woolwich,  in  1S02,*  and  about  the  same  time  it  was  examined 
by  Clement  and  Desormes.t 

It  extinguishes  flame,  and  burns  with  a pale  blue  lambent  light, 
when  mixed  with,  or  exposed  to  atmospheric  air.  The  temperature 
of  an  iron  wire  heated  to  dull  redness  was  found  by  Davy  sufficient 
to  kindle  it. 

515.  A mixture  of  carbonic  oxide  and  oxygen  gases  may  be  made 
to  explode  by  flame,  by  a red-hot  solid  body,  or  by  the  electric  spark. 
If  they  are  mixed  together  in  the  ratio  of  100  measures  of  carbonic 
oxide  and  rather  more  than  50  of  oxygen,  and  the  mixture  is  inflam- 
ed in  Volta’s  eudiometer  by  electricity,  so  as  to  collect  the  product  of 
the  combustion,  the  whole  -of  the  carbonic  oxide,  together  with  50 
measures  of  oxygen,  disappears,  and  100  measures  of  carbonic  acid 
gas  occupy  their  place.  From  this  fact,  first  ascertained  by  Berthollet, 
and  since  confirmed  by  subsequent  observation,  it  follows  that  carbonic 
oxide  contains  half  as  much  oxygen,  aud  as  much  carbon,  as  carbonic 
acid.  Accordingly  its  density  should  be  0.4215  (sp.  gr.  of  carbon  va- 
pour)-|-0.5512  (half  the  sp.  gr.  of  oxygen  gas)  =0.9727,  which  is  the 
number  found  experimentally  by  Dulongand  Berzelius.  Hence  100 
cubic  inches  should  weigh  30.1650  grains.  T. 

516.  It  is  extremely  noxious  to  animals,  and  fatal  to  them  if  con- 
fined in  it.  When  respired  for  a few  minutes  it  produces  giddiness 
and  fainting.  If  pure  it  almost  instantly  causes  profound  coma. 

517.  When  a mixture  of  hydrogen  and  carbonic  acid  gases  is 
electrified,  a portion  of  the  latter  yields  one  half  of  its  oxygen  to  the 
former;  water  is  generated,  and  carbonic  oxide  produced.  On  elec- 
trifying a mixture  of  equal  measures  of  carbonic  oxide  and  protoxide 
of  nitrogen,  both  gases  are  decomposed  without  change  of  volume, 
and  the  residue  consists  of  equal  measures  of  carbonic  acid  and  ni- 
trogen gases.  The  carbonic  oxide  should  be  in  very  slight  excess, 
in  order  to  ensure  the  success  of  the  experiment.  On  this  fact  is 
founded  Henry’s  method  of  analyzing  protoxide  of  nitrogen. 

518.  When  a mixture  of  carbonic  oxide  with  more  than  half  its 
volume  of  oxygen  gas,  is  exposed  over  mercury,  in  contact  with 
spongy  platinum,  to  a temperature  between  300°  and  310°  F.,  it  be- 
gins to  be  converted  into  carbonic  acid,  and  at  a heat  of  a few  de- 


* Nicholson’s  4to  Jour.  v. 


t Ann.  de  Chim.  xxxix. 


161 


Sulphur. 

grees  higher,  is  wholly  acidified  in  the  course  of  a few  minutes.  Sect,  v. 
Mixtures  of  these  two  gases  are,  howfever,  very  slowly  acted  upon  by 
the  platinum  sponge  at  common  temperatures.^ 

519.  None  of  the  metals  exert  any  action  upon  this  gas,  except  By  potassi- 

potassium  and  sodium,  which  at  a red  heat,  burn  in  it  by  abstracting  so' 

its  oxygen,  and  carbon  is  deposited. 

Section  V.  Sulphur. 

Symb.  Sp.  Gr.i  Equiv. 

S.  6.6558  air  =1  By  Vol.  16.66 

96.60  Hyd.=  I “ Wght.  16.1 

520.  Sulphur  is  a brittle  substance,  of  a pale  yellow  colour ; insi-  Properties, 
pid  and  inodorous,  but  exhaling  a peculiar  smell  when  heated.  Its 
specific  gravity  is  1.99.  It  becomes  negatively  electrical  by  heat  and 

by  friction. 

Sulphur  is  principally  a mineral  product,!  and  occurs  massive  and 
crystallized  in  the  form  of  an  oblique  rhombic  octohedron.  Its  crys- 
tals are  in  a high  degree  doubly  refractive. 

Massive  sulphur  is  chiefly  brought  from  Sicily  ; it  occurs  native,  Native  sul- 
and  is  found  associated  with  sulphate  of  lime,  sulphate  ofp  u ’ 
strontia,  and  carbonate  of  lime : it  is  common  among  volcanic 
products.  Sulphur  occurs  also  in  some  mineral  waters,  partly  in 
a free  and  partly  in  a combined  state,  in  combination  with  soda.§ 

Roll-sulphur  is  chiefly  obtained  from  native  metallic  sulphurets,  Roll, 
which  are  roasted  and  the  fumes  received  into  a long  chamber  of 
brick-work,  where  the  sulphur  is  gradually  deposited  : it  is  then  pu- 
rified by  fusion,  and  cast  into  sticks.  It  conducts  heat  imperfectly, 
and,  if  grasped  by  the  warm  hand,  splits  with  a crackling  noise. 

521.  The  fusing  point  of  sulphur  is  216°  F.  Between  230°  and  Action  of 
280°  it  is  as  liquid  as  a clear  varnish,  and  of  the  colour  of  amber  ; tieat‘ 

at  about  320°  it  begins  to  thicken,  and  acquire  a red  colour;  on  in- 
creasing the  heat,  it  becomes  so  thick  that  it  will  not  pour.  From 
482°  to  its  boiling  point  it  becomes  thinner,  but  never  so  fluid  as 
at  248°. 

When  the  most  fluid  sulphur  is  suddenly  cooled,  it  becomes  brit- 
tle, but  the  thickened  sulphur,  similarly  treated,  remains  soft,  and 
more  soft  as  the  temperature  has  been  higher.  In  this  state  it  is  ap-  Use. 
plied  to  taking  impressions  from  engraved  stones,  &c.|| 

522.  Fused  sulphur  has  a tendency  to  crystallize  in  Cooling,  and  Crystalli- 

by  good  management  regular  crystals  may  be  obtained.  zation  of, 

For  this  purpose  several  pounds  of  sulphur  should  be  melted  in  a crucible ; 
and  when  partially  cooled,  the  outer  solid  crust  should  be  pierced,  and  the  cruci- 
ble quickly  inverted  so  that  the  fluid  portion  within  may  gradually  flow  out,  on 
breaking  the  solid  mass,  when  quite  cold,  crystals  of  sulphur  will  be  found  in  the 
interior. 

Fused  sulphur  will  remain  fluid  at  common  temperatures,  and  so- 
lidify when  touched  by  a fragment  of  sulphur  or  a thread  of  glass. 


* Phil.  Trans.  1824,  p.  271.  t In  state  of  vapour. 

t It  is  said  to  have  been  detected  in  several  vegetables  and  in  gum  arabic. — Jame- 
son’s Jour.  xiv.  172.  § Johnson’s  report,  Rep.  Brit.  Assoc.  1832. 

II  See  directions  in  Dumas’s  Traitd  de  Chinn.  1.  135. 

21 


162 


Sulphur. 


Chap.  III. 

Vaporiza- 
tion of. 


Lac  sul- 
phuris. 


Contains 

hydrogen. 


Density  of 
its  vapour. 


Test  of  the 
purity  of 
sulphur. 


Products  of 
its  combus- 
tion. 


Equivalent. 


52 3.  Sulphur  is  very  volatile.  It  begins  to  rise  slowly  in  vapour 
even  before  it  is  completely  fused.  At  550°  or  600°  F.  it  volatilizes 
rapidly,  and  condenses  again  unchanged  in  close  vessels.  Common 
sulphur  is  purified  by  this  process;  and  if  the  sublimation  be  con- 
ducted slowly,  the  sulphur  collects  in  the  receiver  in  the  form  of  de- 
tached crystalline  grains,  called  fioioers  of  sulphur.  In  this  state 
however,  it  is  not  quite  pure  ; for  the  oxygen  of  the  air  within  the 
apparatus  combines  with  a portion  of  sulphur  during  the  process,  and 
forms  sulphurous  acid.  The  acid  may  be  removed  by  washing  the 
flowers  repeatedly  with  water. 

524.  Sulphur  is  insoluble  in  water,  but  has  been  supposed  to  unite 
with  it  under  favorable  circumstances,  forming  what  has  been 
called  Lac  snlphuris  and  hydrate  of  sulphur,  but  which  is  consider- 
ed by  Berzelius  as  sulphur  with  a minute  portion  of  hydrogen.  It  dis- 
solves in  boiling  oil  of  turpentine,  and  is  also  soluble  in  alcohol  if 
both  substances  are  brought  together  in  the  form  of  vapour.  The 
sulphur  is  precipitated  from  the  solution  by  the  addition  of  water. 

525.  Sulphur  retains  a portion  of  hydrogen  so  obstinately  that  it 
cannot  be  wholly  freed  from  it  either  by  fusion  or  sublimation. 
Davy  detected  its  presence  by  exposing  sulphur  to  Voltaic  electricity, 
when  some  hydrosulphuric  acid  gas  was  disengaged.  The  hy- 
drogen, from  its  minute  quantity,  can  only  be  regarded  as  an  acci- 
dental impurity,  and  as  not  essential  to  the  nature  of  sulphur. 

526.  The  density  of  sulphur  vapour  was  found  by  Dumas  to  lie 
between  6.51  and  6.617,  and  by  Mitscherlich  to  be  6.9  its  density 
by  calculation  (page  32)  is  6.6558.  Hence,  could  the  vapour  con- 
tinue as  such  at  60°  F.  and  30  bar.,  100  cubic  inches  should  weigh 
206.4076  grains. 

527.  The  purity  of  sulphur  may  be  judged  of  by  heating  it  gradu- 
ally upon  a piece  of  platinum  leaf ; if  free  from  earthy  impurities,  it 
should  totally  evaporate.  It  should  also  be  perfectly  soluble  in  boil- 
ing oil  of  turpentine. t 

528.  When  sulphur  is  heated  in  the  open  air  to  300°  or  a little 
higher,  it  kindles  spontaneously,  and  burns  with  a faint  blue  light. 
In  oxygen  gas  its  combustion  is  far  more  vivid  ; the  flame  is  much 
larger,  and  of  a bluish  white  colour.  Sulphurous  acid  is  the  pro- 
duct in  both  instances  ; — no  sulphuric  acid  is  formed  even  in  oxygen 
gas  unless  moisture  be  present. 

The  oxygen  in  the  oxide  and  acid  of  neutral  sulphates  is  in  the 
ratio  of  1 to  3 ; so  that  when  the  composition  of  a metallic  oxide, 
and  the  quantity  of  acid  by  which  it  is  neutralized  are  known,  the 
equivalent  of  sulphur  may  be  calculated.  On  this  principle  has 
Berzelius  inferred,  from  the  composition  of  sulphate  of  the  oxide  of 
lead,  that  the  equivalent  of  sulphur  is  16.12;  and  the  number  ob- 
tained by  Turner  in  the  same  way  from  the  same  salt  and  from  sul- 
phate of  baryta,  is  16.09.  As  a mean  of  these  results,  16.1  may  be 
taken  as  the  equivalent  of  sulphur.  The  number  16  is,  for  many 
purposes,  a sufficient  approximation. 


* Ann.  de  Chim • et  de  Phys.  lv.  8. 

tAikin’s  Did ■ article  Sulphur.  It  sometimes  contains  arsenic,  for  detecting 
which  see  Brande’s  Jour.  N.  S.  v. 


Sulphurous  Acid. 


163 


Sulphur  and  Oxygen.  Sulphurous  Acid. 

Composition. 

Form.  Sp.  Gr.  Chem.  Equiv.  Sul.  Oxy.  Equiv, 

S-j-20  or  S 2.2117air  =?l  By  Vol.  100.  16.1  or  1 eq.4-16  or  2 eq.  = 32.1 

32.10  Hyd.=l  “ Wght.  32.1. 


Sect.  V. 


529.  Sulphurous  acid  is  a gaseous  body  and  may  bd  obtained  by  How  ob. 
burning  sulphur  in  common  air  or  oxygen  gas  under  a bell  glass.  tained* 

It  is  also  procured  by  abstracting  part  of  the  oxygen  from  sulphuric 

acid.  This  may  be  done  in  several  ways.  If  chips  of  wood,  straw, 
or  cork,  oil  or  other  vegetable  matters  be  heated  in  strong  sulphuric 
acid,  the  carbon  and  hydrogen  of  those  substances  deprive  the  acid 
of  a part  of  its  oxygen,  and  cpnvert  it  into  sulphurous  acid.  Nearly 
all  the  metals,  with  the  aid  of  heat,  have  a similar  effect. 

530.  The  most  usual  method  is  by  putting  two  parts  by. weight, 
of  mercury,  and  three  of  sulphuric  acid  into  a glass  retort,  and  then 
raising  the  heat;  sulphurous  acid  gas  is  formed,  and  may  be  col- 
lected and  preserved  over  quicksilver.  Half  an  ounce  of  mercury 
is  sufficient  for  the  production  of  several  pints  of  the  gas.  This  gas 
may  also  be  obtained  by  introducing  powdered  charcoal  into  a retort 
and  pouring  over  it  concentrated  sulphuric  acid,  until  on  shaking  it, 
the  mass  appears  moist.  On  heating,  a constant  stream  of  a 
mixture  pf  two  volumes  sulphurous  acid  and  one  of  carbonic  acid 
gases  is  given  off,  which  continues  till  the  mass  becomes  dry,5^ 

As  this  gas  is  heavier  than  air,  when  a mercu- 
rial trough  is  not  at  hand,  the  student  may  collect 
it  in  bottles,  by  the  arrangement  shown  in  Fig. 

150.  The  bent  tube  passes  loosely  through  the 
neck  of  the' receiver,  but  is  fixed  to  the  gas  bottle 
by  means  of  plaster-of-paris  and  water. 

531.  Water  takes  up  33  times  its  bulk  of  this 
gas,  it  must  therefore  be  collected  in  jars  or  bot- 
tles filled  with  mercury  and  over  the  mercurial 
trough,  t 


* Knezaurek  in  Baumgartner’s  Zeitschrift,  lx. 

t The  apparatus  for  collecting  this  and  other  gases  which  are  absorbed  by  water,  is 
similar  to  that  for  collecting  other  gases.  The  trough  may  be  made  of  wood,  marble, 
soapstone,  or,  what  is  preferable,  cast-iron,  well  varnishsd  to  prevent  its  rusting. 

Fig-  151  represents  a convenient  mer^- 
curial  trough  3 whieh  may  be  17  inches 
long,  7 broad,  and  5 deep.  The  mercury 
does  notrpass  under  the  shelf,  so  that  the 
body  of  the  trough  is  only  about  half  as 
broad  below  the  shelf  as  above,  and  it  is 
rounded  at  the  bottom  to  save  an  unneces- 
sary quantity  of  mercury.  The  four  niches' 
a a a a,  at  the  edge  of. the  shelf,  are  to 
receive  the  beaks  of  retorts,  the  jars  being 
placed  over  them  3 the  rods  attached  to  two 
of  the  sides  of  the  trough  are  intended  tr> 

steady  any  tall  jar  left  upon  the  shelf.  Such  a trough  requires  about  140  pounds  of 
mercury,  when  a number  of  jars  are  used.  Also  see  Fig.  105. 

The  jars  for  the  mercurial  trough  should  he  at  least  One  tenth  of  an  inch  in  thick- 
ness, though  not  more  tban-two  inches  in  diameter;  they  ought  also  to  be  ground  at 
the  edges  that  they  may  be  removed  easily,  when  full  of  gas,  on  a flat  glass  plate  rub- 
bed over  with  a little  gasr  lute,  without  losing  auv  of  their  contents.  The  mercurial 
trough  should  be  placed  in  a large  sheet  iron  tray,  to  prevent  the  loss  of  mercury. 
Blotting  paper  is  constantly  required  to  remove  any  acid  or  water  that  may  collect  on 
the  surface  of  the  mercury,  and.  after  auy  gcicl  gas  has  been  prepared  over  it,  the  mer- 


164 


Chap.  III. 
Exp. 


Exp. 


Bleaches. 


Exp. 


Noxious. 


Davy’s  an- 
alysis. 


Decomposi- 

tion. 


Converted 
into  sul- 
phuric acid. 


Sulphur  and  Oxygen. 

Remove  a jar,  filled  with  the  gas,  by  means  of  a flat  glass  plate  held  firmly  to  it, 
or  place  the  thumb  or  finger  on  the  mouth  of  a small  bottle  or  tube  filled  with 
the  gas,  and  take  it  oft  under  water.  The  gas  will  be  absorbed  and  the  water  be 
forced  up  the  vessel  with  violence.  The  acid  property  of  the  gas  will  also  be 
evident  if  the  water  be  coloured  with  purple  cabbage. 

The  experiment  may  be  varied  by  inverting  the  vessel  over  mercury,  and  pass- 
ing a small  quantity  of  water  up  through  the  mercury  ; the  latter  will  rise,  and 
the  water  will  be  seen  to  absorb  many  times  its  own  bulk  of  the  gas. 

532.  Sulphurous  acid  has  considerable  bleaching  properties.  It 
reddens  litmus  papeT,  and  then  slowly  bleaches  it.  Most  vegetable 
colouring  matters,  such  as  those  of  the  rose  and  violet,  are  speedily 
removed,  without  being  first  reddened.  It  is  remarkable  that  the 
colouring  principle  is  not  destroyed  ; for  it  may  be  restored  either  by 
a stronger  acid  or  by  an  alkali.  Prepared  by  the  combustion  of  sul- 
phur, it  is  much  used  for  bleaching  cotton  goods* *  and  also  for  whit- 
ening silk  and  wool ; in  wine  countries  it  is  sometimes  used  to  check 
vinous  fermentation.  It  restores  the  colour  of  sirup  of  violets, 
which  has  been  reddened  by  other  acids. 

A pleasing  instahee  of  its  efTect  on  colours,  may  be  exhibited  by  holding  a 
red  rose  over  the  blue  flame  of  a common  match,  by  which  the  colour  will  be 
discharged  wherever  the  sulphurous  acid  comes  in  contact  with  it,  so  as  to  ren- 
der it  beautifully  variegated,  or  entirely  white.  If  it  be  then  dipped  into  water, 
tlto  tedness,  after  a short  time  will  be  restored. 

533.  This  gas  has  a suffocating  nauseous  odour,  and  an  astrin- 
gent taste  ; it  extinguishes  flame,  and  kills  animals  ; it  is  exceed- 
ingly deleterious  to  vegetables,  even  in  very  minute  quantity  and 
proportion.! 

534.  Davy  proved  that  sulphurous  acid  gas  contains  exactly  its 
own  volume  of  oxygen,!  and  consequently  the  difference  in  the 
weights  or  specific  gravity  of  these  gases  (2.2117 — 1.1024=1.1093), 
gives  the  weight  of  sulphur  combined  with  the  oxygen.  The  sul- 
phur and  oxygen  are  thus  found  to  be  in  the  ratio  of  1.1093  to  1.1024 
or  16.1  to  16.  T. 

535.  Sulphurous  acid  suffers  no  change  at  a red  heat,  but  if  mixed 
with  hydrogen,  and  passed  through  a red-hot  tube,  water  is  formed 
and  sulphur  deposited  ; under  the  same  circumstances,  it  is  also  de- 
composed by  charcoal,  by  potassium  and  sodium,  &c. 

536.  Sulphurous  acid  is  converted  to  the  state  of  sulphuric  acid  by 
restoring  oxygen  to  it. 

A mixture  of  oxygen  and  sulphurous  acid  gases,  both  perfectly 
dry,  and  standing  over  mercury,  is  not  diminished  during  some 
months  ; but  if  a small  quantity  of  water  be  added,  the  mixture  begins 
to  diminish,  and  sulphuric  acid  is  formed.  Or  if  water  impregnated 
with  sulphurous  acid  be  exposed  to  oxygen  gas  in  a tube,  the  oxy- 
gen in  10  or  14  days  is  imbibed  and  sulphuric  acid  formed.  The 

cury  should  always  he  washed  with  water,  and  dried  with  a towel  and  blotting  paper. 
A red-hot  poker  held  for  a short  lime  in  the  mercury  enables  this  to  be  done  more 
effectually  ; it  is  in  this  manner  also,  that  mercury  is  most  conveniently  brought  to  a 
proper  temperature  when  it  is  required  to  be  heated  for  particular  experiments 

The  beak  of  the  retort  must  be  placed  near  the  surface  of  the  mercury,  that  the  gas 
may  have  to  overcome  as  little  resistance  as  possible  in  rising  through  the  heavy  fluid  j 
should  this  not  he  attended  to.  the  retorts  may  he  hroken  by  the  pressure  from  within. 
No  gas  should  he  collected  till  the  atmospheric  air  has  been  all  expelled  from  the  re- 
tort. See  Reid’s  Elements  of  Prac.  Chem. 

* Quart.  Jour,  of  Sci.  iv.  196. 

+ See  Turner’s  experiments  on  the  effect  of  gases  on  vegetables , Brewster’s  Jourm 
Jan.  1828.  t Elements,  273, 


165 


Sulphuric  Acid. 

same  gases  in  a state  of  mixture,  by  the  action  of  electricity  or  by  sect,  v 
being  driven  through  a red-hot  porcelain  tube,  afford  sulphuric  acid. 

The  proportions  required  for  mutual  saturation  are  two  measures  of 
sulphurous  acid  and  one  of  oxygen  gas. 

To  a portion  of  water  saturated  with  sulphurous  acid  gas  add  a little  oxide  Exp. 
of  manganese,  a substance  that  contains  much  oxygen  loosely  combined ; the 
pungent  smell  of  the  water,  and  the  other  characteristics  of  sulphurous  acid  will 
soon  disappear.  H.  1.  385. 

537.  Sulphurous  acid  combines  with  metallic  oxides,  and  forms 
salts  which  are  called  sulphites , which  are  decomposed  by  sulphuric 
acid,  and  then  emit  the  characteristic  odour  of  sulphurous  acid. 

538.  Liquid  sulphurous  acid  is  obtained  by  transmitting  the  dry  Liquid 
pure  gas  through  a glass  tube  surrounded  by  a freezing  mixture  ofaci  ' 
snow  and  salt.  It  boils  at  14°,  and  from  the  rapidity  of  its  evapora- 
tion causes  intense  cold.^ 

539.  Faraday,  by  producing  sulphurous  acid  from  mercury  and  Liquefac- 
concentrated  sulphuric  acid  sealed  up  in  a bent  tube,  obtained  it  in  a 
liquid  state,  very  limpid  and  fluid,  and  quite  colourless.  Its  refrac- acid  gas. 
tive  power  appeared  to  be  nearly  equal  to  that  of  water.  It  does  not 
solidify  at  a temperature  of  0°  F.  When  a tube  containing  it  is 
opened,  it  does  not  rush  out  as  with  an  explosion,  but  a portion  of 

the  liquid  evaporates  rapidly,  cooling  another  portion  so  much  as  to 
leave  it  in  a liquid  state  under  common  barometric  pressure.  It  ra- 
pidly dissipates,  however,  without  appearing  invisible  fumes,  but 
with  a strong  odour  of  sulphurous  acid,  leaving  the  tube  perfectly 
dry,  A piece  of  ice  dropped  into  the  fluid  instantly  made  it  boil 
from  the  heat  communicated  to  it.  The  specific  gravity  of  liquid 
sulphurous  acid  is  about  1.42,  at  45°  F.  it  exerts  a pressure  of  about 
two  atmospheres.! 

Sulphuric  Acid. 

Composition. 

Form.  Sp . Gr.  ( anhydrous ) Chem.  Equiv.  Sulph.  Oxy.  Equiv . 

...  2.7629  air  =1  By  Vol.  100.  16.1  or  1 eq.-p24  or  3 eq— 40.1 

S+30  or  S 40.40  Hyd.^i  “ Wght.  40  1. 

540.  Sulphuric  acid  has  been  long  known  under  the  name  of  oil  Fuming 
of  vitriol,  and  is  supposed  to  have  been  discovered  by  Basil  Yalen-  Nordhau- 
tine  in  the  15th  century.  It  is  prepared  in  large  quantities  for  the  sen. 
purposes  of  the  arts.  At  Nordhausen,  in  Germany,  the  sulphate  of 

oxide  of  iron  (green  vitriol)  is  decomposed  by  heat,  and  a dense  oily 
liquid  of  a dark  colour  is  obtained,  which,  from  its  emitting  white 
fumes,  is  known  as  fuming  sulphuric  acid.  It  has  a specific  gravity 
of  1.896  or  1.90.4 

541.  In  the  United  States  and  most  other  places,  sulphuric  acid  is  Usual  pro- 

manufactured  from  sulphur  and  nitrate  of  potassa.  cess, 

The  mixture  is  burned  in  a large  room  or  chamber  lined  with  lead  and  cover- 
ed to  the  depth  of  several  inches  with  water.  The  sulphur  is  converted  into 
sulphurous  acid  during  its  combustion,  and  a portion  of  it  into  sulphuric  acid  by 
combining  with  some  of  the  oxygen  of  the  nitre,  nitrous  acid  and  binoxide  of  nitro- 
gen being  disengaged.  The  sulphurous  acid  combines  with  the  nitrous  acid  and 
some  watery  vapour,  forming  a crystalline  compound  which  is  decomposed  by 

* See  Bussy’s  process  in  Bost.  Jour,  of  Philos,  ii.  359. 

t Phil.  Trans.  1823,  p.  190.  Sulphurous  acid  is  employed  in  some  diseases  under 
the  name  of  “ Sulphur  baths/’  fora  description  c.f  which,  see  Dumas’  Traits,  v ol.  i.  152. 

? For  details  see  Turner  194,  and  Amer.  Jour  Sci.  xx.  347. 


166 


Chap.  III. 


Theory 

illustrated. 


Impurities. 


Arsenious 

acid. 


Detected. 


Sulphur  and  Oxygen. 

the  water  at  the  bottom  of  the  chamber,  being  converted  into  sulphuric  acid, 
* which  remains  in  combination  with  the  water,  and  binoxide  of  nitrogen  gas, 
which  is  disengaged.  All  the  binoxide  rises  in  the  chamber,  and  mixing  with  a 
fresh  quantity  of  atmospheric  air,  combines  with  the  oxygen  and  forms  a dense 
ruddy  vapour  (nitrous  acid),  which  immediately  falls  down  in  consequence  of  its 
great  specific  gravity,  and  meeting  with  more  sulphurious  acid  and  watery  vapour, 
a crystalline  compound  is  again  formed,  which  is  resolved  as  before  into  sulphuric 
acid  and  binoxide  of  nitrogen.  In  this  manner,  a small  quantity  of  nitre  is  made 
to  communicate  or  hand  over,  as  it  were,  a large  quantity  cf  oxygen  from  the  air 
to  the  sulphurous  acid,  and  the  same  series  of  combinations  and  decompositions 
goes  on  till  the  water  at  the  bottom  of  the  chamber  has  become  strongly  acid. 
It  is  then  boiled  in  leaden  vessels  to  expel  a part  of  the  water,  and  the  concen- 
tration finished  in  large  glass  retorts  in  a sand  bath,  or  in  platinum  retorts  placed 
over  the  open  fire. 

542.  The  theory  of  the  preparation  of  sulphuric  aeid  may  be  illus- 
trated very  beautifully  on  the  small  scale  by  making  sulphurous  acid 
and  nitrous  acid  meet  together  in  a glass  vessel,  and  as  the  experi- 
ment is  intended  solely  for  illustration,  the  sulphurous  acid  may 
be  prepared  by  the  decomposition  of  sulphuric  acid. 

Into  one  of  the  small  retorts,  (Fig  152,) 
which  should  be  large  enough  to  hold 
about  three  or  four  ounces  of  water  when 
full, — put  400  grains  of  mercury  and  <>00 
grains  of  sulphuric  acid,  and  into  the  other 
bO  or  90  grams  of  sugar,  lleat  the  first 
retort  by  a chauffer,  and  when  the  sulphu 
rous  acid  begins  to  come  over,  pour  300 
grains  of  nitric  acid  over  the  sugar,  previ- 
ously diluted  with  an  equal  bulk  of  water, 
and  heat  the  retort  gontly  till  the  nitrous 
acid  fumes  begin  to  come  over,  which  are 
formed  by  the  sugar  attracting  oxygen 
from  the  nitric  acid.  When  the  gases 
meet  in  the  large  jar,  (into  which  the  re- 
torts are  fixed  by  being  ground  to  the  tu- 
bulures,  or  having  their  beaks  passed 
through  corks  fitted  to  them,)  a crystalline  compound  is  soon  deposited  on  the 
sides  of  the  vessel  in  beautiful  dendritical  crystals,  which  often  cover  its  whole 
surface.  Remove  the  retorts  when  either  the  sulphurous  or  nitrous  acid  ceases 
to  come  over,  and  pour  a little  water  into  the  vessel , a brisk  effervescence  will 
take  place  wherever  it  comes  in  contact  with  the  crystalline  compound,  which 
is  resolved  into  binoxide  of  nitrogen  and  sulphuric  acid,  the  former  producing 
ruddy  coloured  fumes  as  it  comes  into  contact  with  the  air,  and  the  latter  being 
retained  in  combination  with  the  water.  Reid. 

543.  Sulphuric  acid  obtained  by  the  usual  process  is  not  pure, 
being  contaminated  by  potassa  and  the  oxide  of  lead,  and  sometimes 
iron,  the  first  derived  from  the  nitre,  and  the  two  latter  from  the 
leaden  chamber.  To  separate  them  the  acid  should  be  distilled 
from  a glass  or  platinum  retort.  The  former  may  be  safely  used  by 
putting  into  it  some  pieces  of  platinum  leaf,  which  causes  the  acid 
to  boil  freely  on  applying  beat,  without  danger  of  breaking  the  ves- 
sel. Arsenious  acid,  derived  from  arsenic  in  the  sulphur  used  in 
the  manufacture,  has  been  lately  detected  in  most  of  the  oil  of  vitriol 
made  in  Germany,  and  from  that  source  arsenic  is  introduced  into 
preparations  for  which  such  acid  is  employed,  as  into  phosphorus  and 
hydrochloric  acid.  It  is  discovered  by  diluting  with  water  and  trans- 
mitting through  the  solution  hydrosulphuric  acid  gas,  which  causes 
orpiment  to  be  formed.  The  oil  of  vitriol  may  be  purified  from  ar- 
senious acid  by  adding  a little  hydrated  peroxide  of  iron  before  dis- 
tilling. T. 


Fig.  152. 


167 


Sulphuric  Acid— Analysis  of. 

j 

The  oil  of  vitriol  of  commerce  often  contains  sulphate  of  lead,  Sect,  v. 
which  may  be  detected  in  the  cold  acid,  by  adding- a few  drops  Hayes’s 
of  hydrochloric  acid.  The  precipitate  is  allowed  to  subside  and  the  testf°r  sul- 
clear  acid  decanted*  feld 

544.  Sulphuric  acid  of  commerce  is  a limpid,  colourless  fluid,  of  properties, 
a thick  and  oily  consistence,  having  a specific  gravity  of  1.84;  it  is 

acrid  and  caustic,  and  even  when  largely  diluted  with  water  produc- 
es a very  sour  liquid. 

545.  It  boils  at  620°  and  freezes  at — 15°,  contracting  at  the  same  Boiling 
time  considerably  in  its  dimensions.  But  the  temperature  at  which  point' 
the  diluted  acid  congeals  is  singularly  modified  by  the  quantity  of 
water  which  it  contains.  At  the  specific  gravity  of  1.780  it  freezes 

at  45°  ; but  if  the  density  be  either  increased  or  diminished,  a great- 
er cold  is  required  for  its  congelation.!  Its  boiling  point  diminish- 
es with  its  dilution. 

546.  It  is  acrid  and  caustic,  and  when  diluted  with  water,  pro- 
duces a very  sour  liquid.  Whep  mixed  suddenly  with  water,  (66)  Mixture 
considerable  heat  is  produced.  Four  parts  by  weight,  of  concentra-  wdh  water, 
ted  sulphuric  acid,  and  one  of  water,  when  mixed  together,  each  at 

the  temperature  of  50°  F.  have  their  temperature  raised  to  300°. 

The  greatest  eleyation  of  temperature,  lire  finds  to  be  occasioned  by 
the  sudden  mixture  of  73  parts  by  weight  of  strong  sulphuric  acid 
with  27  of  water. 

547.  It  rapidly  absorbs  water  from  the  atmosphere.  Even  a Imhlbes 
boiling  temperature,  when  it  is  concentrated,  does  not  prevent  its  018  me* 
taking  up  moisture  from  the  air  ; hence  it  cannot  be  concentrated  so 

well  in  an  open  ;as  in  a close  vessel,  on  which  account,  retorts  of 
glass  or  platinum,  are  used  for  the  last  stage  of  its  concentration  by 
the  manufacturers. 

It  chars  animal  and  vegetable  substances,  and  is  apt  to  acquire  a 
brown  tinge  from  any  small  particles  of  straw,  resin,  or  other  mat- 
ters that  may  accidentally  have  fallen  into  it. 

548.  The  strength  of  sulphuric  acid  is  best  judged  of  by  diluting 

a known  weight  of  the  acid  moderately  with  water,  and  while  ing  the 
warm,  adding  pure  anhydrous  carbonate  of  soda,  until  the  solution  strength  of 
is  exactly  neutral.  Every  53.42  parts  of  the  carbonate  required  to  acid1™”0 
produce  this  effect,  correspond  to  40.1  parts  of  real  sulphuric  acid. 

For  common  purposes  the  strength  of  the  acid  may  be  estimated 
from  its  specific  gravity.! 

549.  The  decomposition  of  sulphuric  acid  may  be  effected  by  pas-  sdphurfc0 
sing  it  through  a red-hot  platinum  tube,  when  it  is  resolved  into  sul-  add, 
phurous  acid,  oxygen  and  water. 

When  heated  with  charcoal,  sulphuric  acid  gives  rise  to  the  pro- 
duction of  carbonic  and  sulphurous  acids  ; with  phosphorus  it. pro- 
duces phosphoric  and  sulphurous  acids;  and,  with  sulphur,  sul- 
phurous acid  is  the  only  product.  It  is  decomposed  by  several  of 
the  metals,  which  become  oxidized,  and  evolve  sulphumus  acid,  as 
shown  in  the  production  of  this  acid,  by  boiling  sulphuric  acid  with 
mercury  (530),  tin,  lead,  &c. 


* Hayes  in  Amer.  Jour.  xvii.  195.  t Keir,  Irish  Phil.  Trans,  iv.  88. 

t For  table  of  strength  of  this  acid  of  different  densities,  see  Appendix. 


168 


Chap.  III. 

By  galvan- 
ism. 

Uses. 


Tests. 


How  ob- 
tained. 


Peculiar 

relations. 


Process. 


Sulphur  and  Oxygen. 

The  liquid  acid  is  also  decomposed  by  platinum  wires,  communi- 
cating with  the  extremities  of  a galvanic  pile. 

550.  Sulphuric  acid  is  largely  consumed  in  a variety  of  manu- 
factures. It  is  used  by  the  makers  of  nitric,  hydrochloric,  citric,  and 
tartaric  acids  ; by  bleachers,  dyers,  tin-plate  makers,  brass-founders, 
gilders,  &c. 

551.  Baryta  in  solution  detects  the  presence  of  sulphuric  acid,  a 
white  insoluble  sulphate  of  baryta  being  precipitated.  The  precipi- 
tate heated  with  charcoal  before  the  blow-pipe  is  decomposed  ; on 
moistening  it  with  water  and  touching  it  with  a solution  of  a salt  of 
lead,  the  sulphur  renders  the  lead  black.  This  acid  gives  a copious 
white  precipitate  with  soluble  salts  of  lead. 

Hyposulphurous  Acid. 

Composition. 

Form.  Sulph.  Oxy.  Equiv. 

2S+20  or  <ij  32.2  or  2 eq.  -f  16or2eq.  = 48.2 

552.  Hyposulphurous  acid  may  be  formed  by  digesting  sulphur 
in  a solution  of  a sulphite  (a  compound  of  sulphurous  acid  and  a 
salifiable  base,)  the  two  equivalents  of  oxygen  in  the  sulphurous 
acid  combining  with  an  additional  quantity  of  sulphur,  and  being 
thereby  converted  into  two  equivalents  of  hyposulphurous  acid.  It 
is  not  easy  to  procure  this  acid  in  a free  state. 

553.  It  is  distinguished  by  the  peculiar  relation  it  has  to  the  oxide 
of  silver,  combining  with  it  in  preference  to  soda,  which  is  easily 
separated  from  this  acid  by  the  oxide,  the  only  instance  where  a me- 
tallic oxide  can  separate  a fixed  alkali  from  an  acid,  without  the  aid 
of  some  other  affinity. 

The  solution  of  all  the  neutral  hyposulphites  dissolves  recently 
precipitated  chloride  of  silver  in  large  quantity,  and  forms  with  it 
a liquid  of  an  exceedingly  sweet  taste. 

Hijposulphuric  Acid. 

Composition. 

Form . Sulph.  Oxy.  Equiv. 

2S+50  or  S 32.2  or  2 eq.  + 40  or  5 eq.  = 72.2 

554.  This  acid  discovered  by  Welter  and  Gay-Lussac  in  1819, 
is  prepared  by  transmitting  sulphurous  acid  through  water  in  which 
finely  powdered  peroxide  of  manganese  has  been  suspended,  a 
portion  of  the  oxygen  of  the  oxide  combining  with  some  of  the  sul- 
phurous acid  and  forming  sulphuric  acid,  part  of  which  unites  with 
the  remaining  sulphurous  acid,  by  which  the  hyposulphuric  acid  is 
produced.  Both  acids  remain  in  combination  with  oxide  of  mangan- 
ese, and  by  adding  baryta  it  is  precipitated,  the  sulphuric  acid  being 
also  thrown  down  in  combination  with  part  of  the  baryta,  while 
the  hyposulphuric  acid  unites  with  the  rest,  and  remains  in  solution. 
By  cautiously  adding  sulphuric  acid  the  baryta  is  removed,  and  the 
hyposulphuric  acid  remains  in  solution.  R. 


Phosphorus „ 


169 


Section  VI.  Phosphorus . 

Symb.  Sp.  Gr.  Chem.  Equiv. 

P.  4.3269  Air  = 1 By  Vol.  25 

62.80  Hyd.  = 1 “ Wght.  15.7 

555 . Phosphorus  (cpcocrydgog  from  (ptig  light  and  (ptgeiv  to  carry), 
so  called  from  its  property  of  shining  in  the  dark,  was  discovered 
about  the  year  1669  by  Brandt,  an  alchemist  of  Hamburgh.  It  was 
originally  prepared  from  urine  ; but  Scheele  afterwards  described  a 
method  of  obtaining  it  from  bones,  which  is  now  generally  prac- 
tised. 

556.  The  object  of  the  process  is  to  bring  phosphoric  acid  in  con- 
tact with  charcoal  at  a strong  red  heat.  The  charcoal  takes  oxy- 
gen from  the  phosphoric  acid  ; carbonic  acid  is  disengaged,  and 
phosphorus  is  set  free. 

As  the  process  for  obtaining  phosphorus  is  tedious  and  not  unat- 
tended with  danger,  and  as  it  can  readily  be  obtained  from  the  drug- 
gist, it  will  be  sufficient  to  illustrate  the  principle  on  which  it  is  pre- 
pared. 

For  this  purpose  30  or  40  grains  of  a mixture  of  phosphoric  acid,  or  of  the 
superphosphate  of  lime,*  with  half  its  weight  of  charcoal  may  be  put  into  a 
glass  tube  sealed  at  one  end,  about  a foot  in  length  and  half  an  inch  in  diameter. 
The  tube  should  be  coated  with  a mixture  of  two  parts  of  clay  and  one  of  sand, 
previously  mixed  with  cut  thread  or  flax,  and  then  wrapped  round  with  iron 
wire.  The  coating  need  not  extend  farther  than  an  inch  beyond  the  part  to 
which  the  mixture  reaches  when  it  has  been  introduced,  as  this  alone  is  to  be 
exposed  to  heat.  It  is  placed  in  a chauffer  with  a hole  cut  in 
the  side,  as  shown  in  the  figure,  and  a chimney  placed  over 
it  to  increase  the  heat ; the  tube  should  be  gently  inclined 
downwards,  to  carry  off-  any  watery  vapour,  and  the  end 
which  is  not  coated  had  better  be  drawn  out  at  the  blow- 
pipe when  the  mixture  has  been  put  in,  till  it  is  about  a 
quarter  or  an  eighth  of  an  inch  in  diameter.  A green  glass 
tube  is  better  than  one  of  flint  glass,  as  it  is  not  so  easily 
melted.  A mixture  of  red  hot  cinders  and  charcoal  gives 
the  best  fire  for  this  experiment.  When  the  heat  has  be- 
come sufficient,  the  phosphorus  comes  over,  condensing 
along  the  sides  of  the  tube,  and  a flame  appears  at  the  open 
end,  similar  to  what  is  produced  by  the  combustion  of  phos- 
phorus. If  the  tube  is  broken  oft'  above  the  point  where  it  is  coated,  after  gas 
ceases  to  be  disengaged,  on  blowing  through  it  the  phosphorus  will  take  fire  and 
burn  with  a vivid  light.  Reid. 

55 7.  Pure  phosphorus  is  transparent  and  almost  colourless.  It  is 
so  soft  that  it  may  be  cut  with  a knife,  and  the  cut  surface  has  a 
waxy  lustre.  At  the  temperature  of  108°  it  fuses,  and  at  550°  is 
converted  into  vapour,  which  according  to  Dumas  has  a sp.  gr. 
of  4.355. 

Phosphorus  is  exceedingly  inflammable.  Exposed  to  the  air  at 
common  temperatures,  it  undergoes  slow  combustion,  emits  a white 
vapour  of  a peculiar  alliaceous  odour,  appears  distinctly  luminous 
in  the  dark,  and  is  gradually  consumed.  On  this  account,  phos- 
phorus should  always  be  kept  under  water. 


* Obtained  by  digesting  calcined  bones  for  a day  or  two  with  half  their  weight  of 
strong  sulphuric  acid,  with  the  addition  of  so  much  water  as  will  give  the  consis- 
tence of  a thin  paste ; sparingly  soluble  sulphate  and  a soluble  superphosphate  of 
lime  are  found.  The  latter  is  dissolved  in  warm  water,  and  after  filtration,  evaporated. 

22 


Fig.  153. 


A 


Sect.  VI. 


Name. 


Process, 


Properties, 


170 


Phosphorus. 


Chap.  III. 


Slow  com- 
bustion. 


Luminous 
in  rarefied 
air. 


Caution- 


Exp. 


Combus- 
tion in  ox- 
ygen. 


The  disappearance  of  oxygen  which  accompanies  these  changes 
is  shown  by  putting  a stick  of  phosphorus  in  a jar  full  of  air,  in- 
verted over  water.  The  volume  of  the  gas  gradually  diminishes  ; 
and  if  the  temperature  of  the  air  is  at  60°,  the  whole  of  the  oxygen 
will  be  withdrawn  in  the  course  of  12  or  24  hours.  The  residue  is 
nitrogen  gas,  containing  about  l-40th  of  its  bulk  of  the  vapour  of 
phosphorus.  It  is  remarkable  that  the  slow  combustion  of  phos- 
phorus does  not  take  place  in  pure  oxygen,  unless  its  temperature 
be  about  80°.  But  if  the  oxygen  be  diluted  with  nitrogen,  hydro- 
gen, or  carbonic  acid  gas,  the  oxidation  occurs  at  60° ; and  it  takes 
place  at  temperatures  still  lower  in  a vessel  of  pure  oxygen,  rarefied 
by  diminished  pressure.  Graham  finds  that  minute  quantities  even, 
of  some  gases  have  [a  remarkable  effect  in  preventing  the  slow  com- 
bustion of  phosphorus.^ 

558,  If  a stick  of  dry  phosphorus  be  dusted  over  with  powdered 
rosin  or  sulphur,  and  then  introduced  under  the  receiver  of  an  air- 
pump,  it  will  be  found  that,  as  soon  as  the  exhaustion  commences, 
the  phosphorus  will  become  luminous,  which  appearance  increases 
as  the  rarefaction  proceeds,  until  finally  the  phosphorus  inflames. 

In  all  experiments  with  phosphorus,  great  care  must  be  taken,  as 
it  is  so  easily  kindled.  It  should  be  cut  under  water  and  be  held 
by  forceps. 

A very  slight  degree  of  heat  is  sufficient  to  inflame  phosphorus 
in  the  open  air.  Gentle  pressure  between  the  fingers,  or  a tempera- 
ture not  much  above  its  point  of  fusion,  kindles  it  readily. 

According  to  Higgins,  a temperature  of  60°  is  sufficient  to  set  it 
on  fire,  when  properly  dry. 

It  may  be  set  on  fire  by  friction.  Rub  a very  small  bit  between  two  pieces 
of  brown  paper ; the  phosphorus  will  inflame,  and  will  set  the  paper  on  fire 
also. 

559.  Its  combustion  is  far  more  rapid  in  oxygen  gas,  and  the 
light  proportionally  more  vivid.t 

This  may  be  done  in  a glass  vessel  of  the  annexed  shape.  (Fig  154.)  It  is 
filled  with  water  after  putting  a cork  into  the  opening  at  the  lop,  placed  on  the 
shelf  of  a large  pneumatic  trough,  in  the  same  manner  as  a jar, 
and  oxygen  gas  introduced  by  the  lower  aperture.  When  quite 
full,  it  is  allowed  to  drain,  removed  on  a flat  plate  of  metal  and 
placed  over  a small  cup  containing  the  phosphorus;  sand  being 
placed  to  the  depth  of  half  an  inch  where  the  jar  is  to  rest.  The 
cork  is  then  taken  out,  and  a thin  plate  of  copper  placed  over  the 
top  after  the  phosphorus  has  been  kindled  by  an  iron  wire ; the 
copper  plate  allows  part  of  the  oxygen  to  escape  freely  when  ex- 
panded by  the  heat.  Corks  should  never  be  put  in  the  mouths  of  the 
vessels,  as  they  are  generally  set  on  fire ; and  if  the  expanded  gas 
cannot  easily  escape,  the  apparatus  will  be  blown  to  pieces.  It  is  often  broken 
also,  when  a large  quantity  of  phosphorus  is  employed.  100  cubic  inches  of 
oxygen  can  combine  with  about  24  grains  of  phosphorus,  but  8 or  ] 0 grains  will 
be  sufficient  for  this  experiment. 


* See  Quart.  Jour.  ofSci.  N.  S.  vi.  83.,  and  note  to  Turner's  Elements , Amer.  EdiL 
■page  198. 

+ For  a method  of  exhibiting  this  with  splendour  and  collecting  the  products,  ses- 
Hare’s  compendiuml  103,. 


171 


Oxide  of  Phosphorus. 


When  a large  jar  is  used  it  will  be  more  convenient  to 
exhaust  the  air,  by  means  of  the  air-pump,  connecting  it 
with  a brass  plate  well  ground  to  the  upper  lip  of  the  jar  ; 

(Fig.  155,)  as  the  air  is  pumped  out  the  water  will  rise  ; 
when  the  jar  is  filled,  the  stop-cock  being  closed,  the 
connecting  pipe  may  be  detached.  Or  if  the  jars  are 
not  too  large,  the  air  may  be  drawn  out  by  the  mouth. 

It  is  not  however,  always  necessary  to  fill  a jar  with 
water,  as  the  gas  from  its  weight,  may  be  passed  in  by 
a pipe  descending  to  the  bottom  and  the  atmospheric  air 
be  displaced,  as  described  page  154. 

560.  When  kept  for  a long  time  under  water,  especially  if  ex-  Effect  of 
posed  to  light,  phosphorus  acquires  a thin  coating  of  white  matter,  kght,  &c' 
which  according  to  Rose*  seems  to  be  phosphorus  in  a peculiar  me- 
chanical state,  which  deprives  it  of  its  usual  action  upon  light,  and 
renders  it  opaque. 

561.  Phosphorus  is  soluble  in  oils,  and  communicates  to  them.  Solution  in 
the  property  of  appearing  luminous  in  the  dark  ; alcohol  and  ether  oll,&c* 
also  dissolve  it,  but  more  sparingly. 

This  may  be  shown  by  pouring  a small  quantity  of  either  of  these  liquids,  Exp. 
in  which  phosphorus  has  been  dissolved,  upon  the  surface  of  warm  water  in 
a dark  room. 

It  is  tasteless  and  insoluble  in  water,  but  proves  poisonous  when 
taken  into  the  stomach. 


Fig.  155. 


Sect.  VT. 


562.  The  researches  by  Berzelius  have  shown  that  the  oxygen  in  Atom  of 
phosphorus  and  phosphoric  acids  is  in  the  ratio  of  3 to  5.  It  js^ph°sPk°' 
hence  inferred  that  the  smallest  molecule  of  phosphoric  acid  con- 
tains five  atoms  of  oxygen.  Also  Berzelius  finds  that  31.4  parts  of 
phosphorus  require  40  of  oxygen  for  fornaing  phosphoric  acid  : if 

this  acid  consist  of  one  atom  of  phosphorus  and  five  atoms  of  oxy* 
gen,  31.4  will  represent  one  atom  of  phosphorus  ; or  if  the  acid 
contain  two  atoms  to  five,  the  atom  of  phosphorus  will  be  half  31.4 
or  15.7.  It  is  doubtful  which  view  is  preferable,  but  we  may  con- 
tinue to  use  15.7  as  its  equivalent.  T.  200. 

563.  Phosphorus  is  largely  consumed  in  the  preparation  of  match-  Uses» 
es  for  obtaining  instantaneous  light.! 


Oxide  of  Phosphorus. 

Composition. 

Form.  Phos.  Oxy.  Equiv. 

3P+0  or  P30  47.1  or  3 eq.  + 8 or  1 eq.  = 55U 

564.  When  a jet  of  oxygen  gas  is  thrown  upon  phosphorus  while  Formation 
In  fusion  under  hot  water,  combustion  ensues,  phosphoric  acid  is  phoSXpho-°f 
formed,  and  a number  of  red  particles  collect,  which  have  been  con- rus. 
sidered  as  oxide  of  phosphorus.  The  red  matter  left  when  phos- 
phorus is  burned  is  probably  of  the  same  nature. 

Place  a few  grains  of  phosphorus  in  a deep  glass,  a champaign  glass  is  the  Exp. 
best,  fill  it  up  with  hot  water,  and  pass  down  upon  the  phosphorus  a stream  of 
oxygen  gas,  by  means  of  a brass  pipe  (the  common  blow-pipe  of  jewellers  made 
straight  answers)  attached  to  a flexible  tube  connected  with  a gasometer  or 
bladder  containing  oxygen  gas. 


* Pog.  Annal.  xxvii.  565. 

t The  matches  are  made  by  attaching  phosphorus  to  the  sulphur  in  which  they 
are  previously  dipped,  or  by  dipping  them  into  a composition  of  phosphorus,  chlorate 
of  potassa,  sulphuret  of  antimony  and  glue.  The  composition  for  what  are  known  as  t^of000*. 
■“  Loco  foco”  matches,  is  a paste  made  with  about  4 parts  of  some  earthy  matter,  as 

Sowdered  chalk,  1 part  phosphorus,  and  1 glue,  dissolved  in  water  with  the  aid  of 
eat ; into  this  the  matches,  previously  prepared  with  sulphur,  are  dipped.  These 
matches  ignite  by  slight  friction. 


172 


Chap.  III. 


Hypophos- 

phorous 

acid. 


Verrier’*  meth- 
od of  obtaining 
pure  oxide  of 
phosphorus. 


Properties 


Phosphorus  and  Oxygen. 

565.  The  oxide  is  of  a red  colour,  without  taste  or  odour,  and  inso- 
luble in  water,  ether,  alcohol,  and  oil.  It  is  permanent  in  the  air, 
even  at  662 3 F.,  but  takes  fire  at  a low  red  heat.  Heated  to  redness 
in  a tube,  phosphorus  is  expelled,  and  metaphosphoric  acid  remains. 
It  takes  fire  in  chlorine  gas,  and  is  rapidly  oxidized  by  nitric  acid. 
It  does  not  appear  to  possess  any  alkaline  character.*  T.  200. 

Hypopkosphorous  Acid. 

Composition. 

Form.  Phos.  Oxy.  Equiv. 

2P+0  or  P20  31.4  or  2 eq.  + 8 or  1 eq.  = 39.4 

566.  This  acid  was  discovered  in  1816  by  Dulong.t  When  water 
acts  upon  the  phosphuret  of  barium  the  elements  of  both  enter  into  a 
new  arrangement,  giving  rise  to  phosphuretted  hydrogen,  phosphor- 
ic acid,  hypophosphorous  acid,  and  baryta.  The  former  escapes  in 
the  form  of  gas,  and  the  two  latter  combine  with  the  baryta.  Hy- 
pophosphite  of  baryta  being  soluble,  may  consequently  be  separated 
by  filtration  from  the  phosphate  of  baryta,  which  is  insoluble.  On 
adding  a sufficient  quantity  of  sulphuric  acid  for  precipitating  the 
baryta,  hypophosphorous  acid  is  obtained  in  a free  state,  and  on 
evaporating  the  solution,  a viscid  liquid  remains,  highly  acid  and 
even  crystallizable,  which  is  a hydrate  of  hypophosphorous  acid. 


* An.  de  Ch.  et  dc  Ph.  1.83. 

Verrier  has  recently  proposed  the  following  method  of  obtaining  pure  oxide  of 
phosphorus,  which,  he  is  of  opinion,  has  not  been  previously  procured.  Take  a glass 
globe,  capable  of  holding  about  two  pints,  the  neck  of  which  is  about  four  inches  long, 
and  one  inch  wide  ; pour  into  this  a little  chloride  of  phosphorus,  then  introduce,  of 
phosphorus,  previously  dried  on  paper,  and  cut  into  pieces  of  about  eight  grains  each, 
enough  to  form  a stratum  of  four  filths  of  an  inch  thick,  at  the  bottom  of  the  globe  ; 
add  sufficient  chloride  of  phosphorus  to  cover  the  phosphorus,  and  expose  the  whole 
to  the  air  5 eight  or  ten  globes  thus  prepared  are  required  to  obtain  thirty  grains  of 
oxide.  In  twenlyfour  hours,  a thick  white  crust  of  phosphatic  acid  is  formed  at  the 
surface  of  the  solution,  whilst  below  the  stratum  of  phosphorus  a yellow  subslauce  is 
seen  which  is  a compound  of  phosphoric  acid  and  oxide  of  phosphorus,  called  by  Ver- 
rier phosphate  of  oxide  of  phosphorus. 

In  twentyfour  hours  after  the  appearance  of  the  whitish  matter,  the  chloride  of 
phosphorus  is  poured  off,  to  serve  lor  another  operation ; the  pieces  of  phosphorus  are 
detached  and  gradually  allowed  to  fall  into  cold  water.  The  water  becomes  of  a deep 
yellow  colour  from  dissolving  the  phosphate  5 by  decanting  and  filtering  a limpid  yel- 
low liquid  is  obtained.  By  heating  this  solution,  the  phosphate  decomposes  at  about 
177°  F.  into  phosphoric  acid,  and  a yellow  flocculent  matter,  which  collects  at  the  bot- 
tom, and  is  considered  as  hydrated  phosphoric  acid,  nearly  iusoluble  in  water.  This 
is  washed  upon  a filter  with  hot  water,  removed  from  it  while  moist,  to  a porcelain 
capsule,  and  dried  in  r acuo  over  sulphuric  acid.  The  oxide  of  phosphorus  remains 
pure,  in  the  form  of  small  grains  of  a red  colour,  but  when  in  fine  powder,  of  canary 
yellow.  Its  composition  according  to  Verrier  is 

Oxy.  11.35  Phos.  88.65 

It  is  insoluble  in  water,  alcohol,  and  ether;  it  is  denser  than  water.  When  removed 
from  the  vacuum  it  has  neither  taste  nor  smell,  but  is  acidified  by  moist  air  or  oxygen 
yielding  a slight  odour  of  phosphuretted  hydrogen.  It  is  not  luminous  in  the  dark. 

Out  of  contact  of  the  air  it  may  be  kept  at  a temperature  of  about  570°  without 
decomposing,  but  becomes  of  a bright  red  colour.  At  a temperature  a little  below  that 
of  boiling  mercury,  it  decomposes  rapidly,  phosphorus  distils,  and  white  phosphoric 
acid  remains.  Heated  in  the  air  it  is  unchanged,  and  burns  only  when  it  disengages 
phosphorus.  Chlorine  converts  it  into  chloride  of  phosphorus  and  phosphoric  acid. 
Nitric  acid  converts  it  into  phosphoric  acid. 

Mixed  with  chlorate  of  potassa  it  gives  a fulminating  powder,  which  detonates  some- 
times during  the  mixture,  and  without  pressure;  it  always  explodes  under  slight 
pressure  The  hydrate  was  inferred  to  contain  20.5  per  cent,  of  water,  its  composition 
being  very  nearly  oxide  1 eq.  water  2.  Ann . de  Chim.  et  de  Phys.  July,  1837,  and 
Lond.  and  Edin.  Phil.  Mag.  Oct.  1838.  t An.  de  Ch.  et  Ph.  ii. 


173 


Phosphoric  Acid . 


Hypophosphorous  acid  is  a powerful  deoxidizing  agent.  It  unites  aect.  Vf» 
with  alkaline  bases;  and  it  is  remarkable  that  all  its  Salts  are  solu- 
ble in  water. 


Form . 

2P+30,  P or  P203 


Phosphorous  Acid . 

Composition. 

Phos.  Oxy. 

31.4  or  2 eq.  + 24  or  3 eq. 


Equiv. 

55.4 


/ 


567.  Phosphorous  acid  may  be  procured  by  subliming  phosphorus  Phospho- 
through  powdered  bichloride  of  mercury  contained  in  a glass  tube  ; Gained 
when  a limpid  liquid  comes  over,  which  is  a compound  of  chlorine 

and  phosphorus.^  This  substance  and  water  mutually  decompose 
each  other : the  hydrogen  of  water  unites  with  the  chlorine,  and 
forms  hydrochloric  acid;  while  the  oxygen  attaches  itself  to  the 
phosphorus,  and  thus  phosphorous  acid  is  produced.  The  solution  is 
then  evaporated  to  the  consistence  of  sirup  to  expel  the  hydrochloric 
acid ; and  the  residue,  which  is  hydrate  of  phosphorous  acid,  be- 
comes a crystalline  solid  on  cooling.  It  is  also  generated  during  the 
slow  oxidation  of  phosphorus  in  atmospheric  air.  The  product  at- 
tracts moisture  from  the  air,  and  forms  an  oil-like  liquid. 

568.  It  dissolves  readily  in  water,  has  a sour  taste,  and  smells  Properties, 
somewhat  like  garlic.  It  unites  with  alkalies,  and  forms  salts  which 

are  termed  'phosphites.  The  solution  of  phosphorous  acid  absorbs 
oxygen  slowly  from  the  air,  and  is  converted  into  phosphoric  acid. 

From  its  tendency  to  unite  with  an  additional  quantity  of  oxygen,  it 
is  a powerful  deoxidizing  agent  ; and  hence,  like  sulphurous  acid, 
precipitates  mercury,  silver,  platinum,  and  gold  from  their  saline 
combinations  in  the  metallic  form.  Nitric  acid  converts  it  into  phos- 
phoric acid. 


Phosphoric  Acid. 


Form. 

2P+50,  P,  or  PQ5t 


Composition. 

Phos.  Oxy. 

31.4  or  2 eq.  + 40  or  5 eq. 


Equiv, 
— 71.4 


569.  In  1S27,  Clarke  of  Aberdeen,  showed  that  under  the  term  Phosphoric 
phosphoric  acid , had  previously  been  confounded  two  distinct  acids,  acids 
one  of  which  he  proposed  to  distinguish  by  the  name  of  pyrophos - 
phoric  acid  (from  uvq  fire ,)  to  indicate  that  it  is  phosphoric  acid 
modified  by  heat ; and  Graham  has  described  another  to  which  he 
has  given  the  provisional  name  of  metaphosphoric  (from  yexa  togeth- 
er with),  implying  phosphoric  acid  and  something  besides.  These 
acids  contain  phosphorus  and  oxygen  in  the  same  ratio,  and 
have  the  same  equivalent,  so  that  they  maybe  considered  as  isomeric 
bodies  (page  36)  ; but  that  difference  in  the  arrangement  of  their 
elements  on  which  their  peculiarities  may  be  presumed  to  depend, 
is  very  slight,  since  they  are  easily  convertible  into  each  other.! 

* Davy’s  Elements , p.  288. 

+ But  as  it  cannot  exist  uncombined,  it  is  best  denoted  by  X3  PO5,  where  X repre- 
sents an  equivalent  of  water,  or  any  base.  T,  203. 

t Phil . Trans . 1833,  part  ii.,  and  Phil.  Mag.  3d  Series,  iv.  401. 


174 


Chap,  ill. 


Exp. 


Process. 


Properties. 


Unites 
with  bases. 


Test. 


Pyrophos- 
phoric acid. 


Metaphos- 
phoric  acid. 


Phosphorus  and  Oxygen. 

570.  Phosphoric  acid  may  be  obtained  by  oxidizing  phosphorus 
by  strong  nitric  acid  ; but  great  care  is  required  as  the  action  is  often 
very  violent,  attended  with  a rapid  evolution  of  great  quantities  of 
binoxide  of  nitrogen. 

Place  a few  fragments  of  phosphorus  in  a deep  and  strong 
glass  vessel,  of  the  form  represented  in  the  figure.  (Fig.  156.) 

Pour  upon  it,  from  a vessel  attached  to  the  end  of  a long  stick, 
an  ounce  or  more  of  nitric  acid  recently  prepared  from  nitre 
and  sulphuric  acid.  If  the  acid  is  very  strong  and  warm,  vio- 
lent and  dangerous  explosion  often  occurs,  and  the  acid,  frag- 
ments of  phosphorus  and  of  glass  are  thrown  to  a considerable 
distance.  A platinum  vessel  is  preferable,  and  should  be 
firmly  secured  to  the  table. 

571.  Phosphoric  acid  may  be  prepared  at  a much 
cheaper  rate  from  bones.  For  this  purpose,  super- 
phosphate of  lime,  obtained  in  the  way  already  de- 
scribed, (556)  should  be  boiled  for  a few  minutes 
with  excess  of  carbonate  of  ammonia.  The  lime  is  thus  precipitated 
as  a phosphate,  and  the  solution  contains  phosphate,  together  with  a 
little  sulphate  of  ammonia.  The  liquid,  after  filtration,  is  evapora- 
ted to  dryness,  and  then  ignited  in  a platinum  crucible,  by  which 
means  the  ammonia  and  sulphuric  acid  are  expelled. 

572.  Phosphoric  acid  is  colourless,  intensely  sour,  reddens  litmus, 
and  neutralizes  alkalies.  It  is  concentrated  by  evaporation  at  300° 
F.,  and  becomes  dark,  and  thick  as  treacle  when  cold.  It  consists 
of  71.4  parts  or  1 equiv.  phosphoric  acid  and  27  parts  or  3 equiv. 
water. 

573.  Phosphoric  acid  is  remarkable  for  its  tendency  to  unite  with 
alkaline  bases,  in  such  proportions  that  the  oxygen  of  the  base  and 
of  the  acid  is  as  3 to  5 ; or,  in  other  words,  it  is  prone  to  form  sub- 
salts, in  which  one  equivalent  of  acid  is  combined  with  three  equiv- 
alents of  base.  It  manifests  the  same  character  in  regard  to  water, 
and  ceases  to  be  phosphoric  acid  unless  three  equivalents  of  water 
to  one  of  acid  are  present ; it  even  appears  that  the  water  acts  the 
part  of  a base,  hence  called  basic  water,  and  that  the  aqueous  solu- 
tion is  not  a mere  solution  of  phosphoric  acid,  but  of  triphosphate  of 
water,  a sort  of  salt  composed  of  one  equivalent  of  acid  and  three 
equivalents  of  water.  Part  of  this  basic  water  enters  along  with 
soda  into  the  constitution  of  two  of  the  phosphates  of  soda,  the 
water  and  soda  together  forming  the  three  equivalents  of  base  re- 
quired by  one  equivalent  of  the  acid.  T.  202. 

574.  A certain  test  between  phosphoric  and  arsenious  acids  is, 
that  the  former  is  neither  changed  in  colour  nor  precipitated 
when  a stream  of  hydrosulphuric  acid  gas  is  transmitted  through  it ; 
while  the  latter,  with  the  required  precautions,  first  acquires  a yel- 
low tint,  and  then  yields  a yellow  precipitate. 

575.  Pyrophosphoric  Acid. — This  acid  is  formed  by  exposing  con- 
centrated phosphoric  acid  for  some  time  to  a heat  of  415°.  Its  general 
characters  resemble  those  of  phosphoric  acid ; it  is  remarkable  for 
its  tendency  to  unite  with  two  equivalents  of  a base. 

576.  Metaphosphoric  Acid , HO.P2Os,  is  obtained  by  burning 
phosphorus  in  dry  air  or  oxygen  gas,  or  heating  to  redness  a con- 
centrated solution  of  phosphoric  or  pyrophosphoric  acids. 


Fig.  156. 


Boron — Boracic  Acid. 


175 


577.  The  peculiarity  of  this  acid  is  to  combine  with  one  equiva-  Sect,  vn. 
lent  of  a base.  On  exposing  the  anhydrous  acid  to  the  air  it  rapidly  Peculiarity, 
deliquesces,  and  at  the  same  time  acquires  its  basic  water,  which 
can  only  be  replaced  by  an  equivalent  quantity  of  soda  or  some  other 
alkaline  base.  The  pure  hydrated  acid  is  of  itself  very  fusible,  and 
on  cooling  concretes  into  a transparent  brittle  solid,  being  known  un- 
der the  name  of  glacial  'phosphoric  acid , which  is  highly  deliquescent,  Glacial 
and  can  hence  only  be  preserved  in  its  glassy  state  in  bottles  care-  ac^d* 
fully  closed.  This  acid  when  free,  occasions  precipitates  in  solu- 
tions of  the  salts  of  baryta,  and  most  of  the  earths  and  metallic  ox- 
ides, and  forms  an  insoluble  compound  with  albumen. 


Section  VII.  Boron. 

Symb.  B.  Equiv.  10.9  eq.  vol.  = 100 

578.  Boron  was  discovered  by  Davy,  by  the  action  of  Voltaic  Boron, 
electricity  upon  boracic  acid,  hence  its  name.  It  was  also  obtained 

by  Gay-Lussac  and  Thenard  in  1808,^  by  heating  boracic  acid  with 
potassium,  the  boracic  acid  being  deprived  of  its  oxygen  and  the  bo- 
ron set  free.  The  easiest  method,  according  to  Berzelius,  is  to  de- 
compose borofluoride  of  potassium  or  sodium  by  means  of  potas- 
sium.! 

579.  Boron  is  a dark  olive-coloured  substance,  which  has  neither  Properties, 
taste  nor  smell,  and  is  a non-conductor  of  electricity.  It  is  insoluble 

in  water,  alcohol,  ether  and  oils.  It  does  not  decompose  water.  It 
bears  intense  heat  in  close  vessels,  without  fusing  or  undergoing  any 
other  change  except  a slight  increase  of  density.  Its  specific  gravity 
is  about  twice  as  great  as  that  of  water.  It  may  be  exposed  to  the 
atmosphere  at  common  temperatures  without  change ; but  if  heated 
to  600°,  it  suddenly  takes  fire,  oxygen  gas  disappears,  and  boracic 
acid  is  generated.  It  also  passes  into  boracic  acid  when  heated  with 
nitric  acid,  or  with  any  substance  that  yields  oxygen  with  facility. 

580.  According  to  the  experiments  of  Davy  and  Berzelius,  boron  Union  with 
in  burning  unites  with  200  per  cent,  of  oxygen  ; and  the  latter,  from  Oxygen- 
the  composition  of  borax,  estimates  the  oxygen  in  boracic  acid  at 

68.8  per  cent. 

Boracic  Acid. 

Symb.  B-r30,  B or  BO3  Equiv.  34.9 

581.  This  is  the  only  known  compound  of  boron  and  oxy-  Boracic 
gen.  It  is  found  in  the  hot  springs  of  Lipari,  and  in  those  of  acid. 

Sasso  in  the  Florentine  territory.  It  is  a constituent  of  several  mi- 
nerals, as  the  datholite  and  boracite.  It  occurs  much  more  abun- 
dantly under  the  form  of  borax , a native  compound  of  boracic  acid 

and  soda. 

582.  It  is  prepared  for  chemical  purposes  by  adding  sulphuric  acid  Process, 
to  a solution  of  purified  borax  in  about  four  times  its  weight  of  boil- 


* See  the  original  memoirs  in  the  Ann.  de  Chim.  et  de  Phys.  xxvi.  66,  113,  and 
an  abstract  in  the  Quart • Jour,  xviii.  149. 

f Ann.  Philos,  xxvi.  128. 


176 


Silicon . 


Chap.  III. 


Properties. 


Effect  of 
heat. 


Discovery. 


How  ob- 
tained. 


Properties. 


ing  water,  till  the  liquid  acquires  a distinct  acid  reaction.  The  sul- 
phuric acid  unites  with  the  soda ; and  the  boracic  acid  is  deposited, 
when  the  solution  cools,  in  a confused  group  of  shining  scaly  crys- 
tals. It  is  then  thrown  on  a filter,  washed  with  cold  water  to  sepa- 
rate the  adhering  sulphate  of  soda  and  sulphuric  acid,  and  still 
further  purified  by  solution  in  boiling  water  and  re-crystallization. 
It  is  apt  to  retain  a little  sulphuric  acid  ; and  on  this  account,  when 
required  to  be  absolutely  pure,  it  should  be  fused  in  a platinum  cru- 
cible, dissolved  in  hot  water  and  crystallized. 

533.  Boracic  acid  in  this  state  is  a hydrate,  which  contains  43.62 
per  cent,  of  water,  being  a ratio  of  34.9  parts  or  one  equivalent  of 
the  anhydrous  acid  to  27  parts  or  three  eq.  of  water.  This  hydrate 
dissolves  in  25.7  times  its  weight  of  water  at  60°,  and  in  3 times  at 
212°.  Boiling  alcohol  dissolves  it  freely,  and  the  solution,  when  set 
on  fire,  burns  with  a beautiful  green  flame  ; a test  which  affords  the 
surest  indication  of  the  presence  of  boracic  acid.  Its  specific  gravity 
is  1.479.  It  has  no  odour,  and  its  taste  is  rather  bitter  than  acid. 
It  reddens  litmus  paper  feebly,  and  effervesces  with  alkaline  carbo- 
nates. Its  acid  properties  are  weak,  and  the  borates,  when  in 
solution,  are  decomposed  by  the  stronger  acids. 

5S4.  When  exposed  to  a gradually  increasing  heat  in  a platinum 
crucible,  the  water  of  crystallization  is  expelled,  and  a fused  mass 
remains,  which,  on  cooling,  forms  a hard,  colourless,  transparent 
glass,  which  is  anhydrous  boracic  acid.  If  the  water  of  crystalliza- 
tion be*driven  off  by  the  sudden  application  of  a strong  heat,  a large 
quantity  of  boracic  acid  is  carried  away  during  the  rapid  escape  of 
watery  vapour.  Vitrified  boracic  acid  should  be  preserved  in  well- 
stopped  vessels;  for  if  exposed  to  the  air,  it  absorbs  water,  and  gra- 
dually loses  its  transparency.  Its  specific  gravity  is  1.803.  It  is 
exceedingly  fusible,  and  communicates  this  property  to  the  substances 
with  which  it  unites.  For  this  reason  borax  is  often  used  as  a flux. 


Section  VIII.  Silicon. 

Symb.  Si.  Equiv.  22.6 

535.  It  was  shown  by  Davy  tbat  silica  is  a compound  of  a com- 
bustible body  and  oxygen,  to  which  the  name  silicium  was  given,  but 
which  is  now  termed  silicon.  Silicon  was  obtained  by  Berzelius  in 
1824,  by  the  action  of  potassium  on  fluosilicic  acid  gas ; it  may  be 
more  conveniently  prepared  from  the  double  fluoride  of  silicon  and 
potassium,  or  sodium,  heated  in  a glass  tube  with  potassium, 
which  unites  to  the  fluorine  and  the  silicon  is  separated,  united 
with  a little  hydrogen.  It  is  purified  by  a red  heat  and  digestion  in 
dilute  hydrofluoric  acid.* 

536.  Silicon  has  a dark  brown  colour,  but  no  metallic  lustre.  It 
is  a non-conductor  of  electricity. 

Before  ignition  it  is  not  oxidized  or  dissolved  by  sulphuric,  nitric, 
or  nitro-hydrochloric  acids,  but  is  soluble  in  hydrofluoric  acid,  and 
in  a hot  concentrated  solution  of  caustic  potassa.  It  undergoes  par- 
tial combustion  in  air  and  oxygen  gas. 


* Ann.  Philos,  xxvi.  116. 


Silicic  Acid — Silica. 


177 


After  combustion  on  its  surface  the  silica  is  removed,  by  hydro-  Sect,  vm. 
fluoric  acid,  and  the  silicon  within  is  insoluble.  A difference  attribu- 
ted by  Berzelius  to  a difference  in  the  aggregation  of  the  particles.^ 

5S7.  Silicon  is  not  changed  by  ignition  with  chlorate  of  potassa.  Oxidation 
In  nitre  it  does  not  deflagrate  until  the  temperature  is  raised  so  high  °r- 
that  the  acid  is  decomposed.  It  burns  vividly  when  brought  into 
contact  with  carbonate  of  potassa  or  soda,  and  the  combustion  en- 
sues at  a temperature  considerably  below  that  of  redness.  It  ex- 
plodes in  consequence  of  a copious  evolution  of  hydrogen  gas,  when 
it  is  dropped  upon  the  fused  hydrate  of  potassa,  soda,  or  baryta. 

588.  Berzelius  ascertained,  by  oxidizing  a known  weight  of  sili- Equivalent, 
con,  that  100  parts  of  silicic  acid  are  composed  of  48.4  of  silicon  and 
51.6  of  oxygen.  Now  if  silicic  acid,  as  Thomson  supposes,  be  com- 
posed of  single  atoms  of  its  elements*  then  the  equivalent  of  silicon 
will  be  7.5 ; but  if,  as  Berzelius  believes,  the  smallest  molecule  of 
that  acid  contain  three  atoms  of  oxygen  united  with  one  atom  of 
silicon,  the  equivalent  of  silicon  would  be  22.5.  The  latter  view  is 
supported  by  very  strong  analogies.  T. 


589.  Silica  or  siliceous  earth  is  an  abundant  natural  product,  con-  Abundant 
stitutmg  a principal  ingredient  of  extensive  mountain  masses,  of 

sand,  and  of  several  minerals  as  quartz,  calcedony,  opal,  &c.  It  is 
an  important  part  of  fertile  soils,  rendering  them  porous  and  open  to 
the  transmission  of  water.  It  abounds  in  the  natural  hot  springs  of 
Iceland  and  of  the  Azores,!  and  is  probably  an  universal  Ingre- 
dient in  thermal  waters.  It  exists  in  the  epidermis  of  most  monoco- 
tyledonous  plants.! 

590.  The  purest  form  of  silica  is  rock  crystal,  from  which  it  obtained 
may  be  procured  of  sufficient  purity  for  most  purposes,  by  ignition,  pure, 
quenching  in  cold  water  and  reduction  to  powder. § 

591.  Silica  is  white  ; its  sp.  gr.  is  2.69  ; it  requires  a very  high  Properties, 
temperature  for  fusion.  In  its  ordinary  state  it  is  insoluble  in  water ; 

but  if  presented  to  water  while  in  the  nascent  state  it  is  dissolved  in 
large  quantities. ih 

592.  Silica  has  no  action  on  test  paper,  but  in  its  chemical  rela-  Acid, 
tions  it  exhibits  the  properties  of  an  acid,  and  displaces  carbonic  acid 

by  the  aid  of  heat  from  the  alkalies,  hence  it  has  been  called  silicic 
acid. 

593.  On  gently  evaporating  its  solution  in  water,  a bulky  gelatin-  Action  of 
ous  hydrate  separates,  which  is  partially  decomposed  by  a very  heat- 
moderate  temperature,  but  it  does  not  part  with  all  its  water  except 

at  a red  heat. 

594.  On  igniting  one  part  of  silicic  acid  with  three  of  carbonate  Liquor 
of  potassa,  a vitreous  mass  is  formed,  which  is  deliquescent,  and  silicum. 


* Berzelius,  TraiU  de  Chem.  1,370.  t See  Webster’s  Azores. 

f See  Daubeny’s  Report  oil  Waters,  in  Rep.  Brit.  Assoc,  v. 

§ For  minute  details  see  Henry’s  Chem.  i.  643.  ||  Berzelius. 


Silicic  Acid — Silica . 


Symb. 

Si+30,  Si,  or  Si03 


Equiv. 

46.5 


23 


178 


Chap.  III. 


Glass. 


Varieties. 


Annealing. 


Sources  of 
selenium, 


Selenium. 

may  be  dissolved  completely  in  water.  This  solution  was  formerly 
called  liquor  silicum ; it  has  an  alkaline  reaction,  and  absorbs  car- 
bonic acid  on  exposure  to  the  atmosphere  by  which  it  is  partially  de- 
composed. 

595.  With  one  part  of  alkali  and  three  of  silicic  acid  the  well 
known  compound  glass  is  formed.  Every  kind  of  ordinary  glass  is 
a silicate,  and  its  varieties  are  owing  to  differences  in  the  proportion 
of  the  constituents,  to  the  nature  of  the  alkali,  or  to  the  presence  of 
foreign  matters.  Bottle  glass  is  obtained  from  common  sand,  which 
contains  iron,  and  the  most  common  kind  of  kelp  or  pearlashes. 
Croion  glass  for  windows  is  made  of  a purer  alkali  and  sand  which 
is  free  from  iron.  Plate  glass  for  looking-glasses,  is  composed  of 
gand  and  alkali  in  their  purest  state  ; and  in  the  formation  of  Flint 
glass,  besides  these  pure  ingredients,  a considerable  quantity  of 
litharge  or  red  lead  is  employed.* * * §  A small  portion  of  peroxide  of 
manganese  is  also  used,  in  order  to  oxidize  carbonaceous  matters 
contained  in  the  materials;  and  nitre  with  the  same  intention.! 

596.  Glass  vessels  must  be  cooled  very  slowly,  or  annealed , other- 
wise they  are  very  brittle.  When  properly  prepared,  glass  is  acted 
upon  by  few  chemical  agents.!  Hydrofluoric  acid,  however,  attacks 
the  silica. § The  metallic  bases  of  the  alkalies  appear  to  decompose 
it;  and  Davy  found  that  oxide  of  lead  in  fine  glass,  is  acted  upon 
by  hydrochloric  acid  at  a high  temperature,  chloride  of  lead  and 
Water  being  formed. 


Section  IX.  Selenium. 

Symb.  Sp.  Gr.  Equiv. 

Se  4.3  39.6 

597.  Selenium  was  discovered  in  ISIS  by  Berzelius  in  the  sul- 
phur obtained  by  sublimation  from  the  iron  pyrites  of  Fahlun  in 
Sweden.  It  exists  as  a sulphuret  among  the  volcanic  products  of 
the  Lipari  islands ; and  in  other  places,  combined  with  metals. 

In  the  chambers  for  manufacturing  sulphuric  acid,  a reddish  mass 


* For  many  chemical  processes  glass  vessels  free  from  lead  should  be  employed. 
Those  made  of  German  potash  glass,  or  hard  white  glass  free  from  lead,  can  now  be 
obtained  of  any  required  form  or  size,  from  Richard  Griffin  &.  Co.  Glasgow,  Scot- 
land, and  I have  found  them  exceedingly  durable  and  well  adapted  to  all  required 
purposes.  W. 

t The  art  of  colouring  glass  and  of  making  artificial  gems  is  of  an  old  date,  and 
effected  by  metallic  oxides.  The  metals  employed  as  colouring  materials  are  1.  Gold. 
The  purple  of  cassius  imparts  a fine  ruby  tint.  2.  Silver,  oxide  or  phosphate  of  sil- 
ver gives  a yellow  colour.  3.  Iron-oxides,  produce  green,  yellow,  and  brown.  4.  Cop- 
per-oxides, green  ; with  a small  proportion  of  tartar,  the  oxides  produce  a red.  5.  An- 
timony, gives  a rich  yellow.  6.  Manganese,  the  black  oxide  in  large  quantity  gives  a 
black,  in  smaller  quantities  various  shades  of  purple.  7.  Cobalt,  blue.  8.  Chrome, 
greens  and  reds,  according  to  the  degree  of  oxidaiion.  On  this  subject  see  Neri 
Art  de  la  Vcrrerie , Ann.  de  Chim,.  et  Phys.  xiv.  57.  Aikin’s  Did’y.  Art.  Glass. 
Dumas  Traite  de  Chim.  II.  531. 

White  enamel  is  merely  glass  rendered  more  or  less  opaque  by  oxide  of  tin ; it 
forms  the  basis  of  the  coloured  enamels,  which  are  tinged  with  the  metallic  oxides. 

t Turner  found  that  steam  under  high  pressure  becomes  a rapid  solvent  of  alkaline 
silicates.  Geol.  Trans.  Lond.  ii.  95. 

§ For  a method  of  exposing  siliceous  substances  to  hydrofluric  acid  see  Lond.  and 
Ed.  Philos.  Mag-,  xiii-  473. 


179 


Oxide  of  Selenium . 

is  deposited,  which  is  principally  sulphur.  This  .substance,  in  burn-  sect,  ix. 
ing,  gave  out  an  odour,  which  induced  Berzelius  to  suspect  that  it 
contained  tellurium,  but  on  a minute  examination  he  discovered,  in- 
stead  of  that  metal,  a body  with  entirely  new  properties,  to  which  he 
has  given  the  name  of  Selenium , from  2elr^vrj  the  moon. 

598.  For  the  extraction  of  selenium  from  the  native  sulphu ret,  Extraction 
Magnus  proposes  to  mix  it  with  eight  times  its  weight  of  peroxide  of of' 
manganese,  and  to  expose  the  mixture  to  a low  red  heat  in  a glass 

retort,  the  beak  of  which  dips  into  water.  The  sulphur,  oxidized  at 
the  expense  of  the  manganese,  escapes-  in  the  form  of  sulphurous 
acid  ; while  the  selenium  either  sublimes  as  such  or  in  the  state  of 
selenious  acid.  Should  any  of  the  latter  be  carried  over  into  the 
water,  it  would  there  be  reduced  by  the  sulphurous  acid. 

599.  The  colour  of  Selenium  varies  a good  deal.  When  rapidly  Properties, 
cooled,  its  surface  has  a dark  brown  hue,  and  its  fracture  the  colour 

of  lead.  Its  powder  has  a deep  red  colour,  but  it  sticks  together 
when  pounded,  and  then  assumes  a gray  colour  and  a smooth  sur- 
face. Its  specific  gravity  is  between  4.3  and  4.32.  It  softens  at  212° 

F.,  and  completely  fuses  at  a few  degrees  higher.  While  cooling, 
it  has  a considerable  degree  of  ductility,  and  may  be  kneaded  be- 
tween the  fingers,  and  drawn  out  into  fine  threads,  which  have  a 
strong  metallic  lustre,  and  are  red  by  transmitted  light.  When, 
slowly  cooled  it  assumes  a granulated  fracture,  and  is  extremely  like 
a piece  of  cobalt.  It  boils  at  about  650°,  its  vapour  has  a deep  yel- 
low colour,  and  condenses  either  into  opaque  metallic  drops,  or, 
when  a retort  with  a large  neck  is  used,  into  flowers  of  a fine  cinna- 
bar colour. 

600.  When  heated  before  the  blow-pipe,  if  tinges  the  flame  of  a Tinges 
fine  azure  blue,  and  exhales  so  strong  a smell  of  horse-radish,  that  flame‘ 
a fragment,  not  exceeding  5V°f  a grain,  is  sufficient  to  fill  the  air  of 

a large  apartment. 

601.  Berzelius  at  first  regarded  it  as  a metal ; but,  since  it  is  an 
imperfect  conductor  of  heat  and  electricity,  it  more  properly  belongs 

to  the  class  of  the  simple  non-metallic  bodies.  He  has  shown  that  Equive^pnt 
selenic  acid  is  composed  of  24  parts  of  oxygen  and  39.6  of  selenium. 

This  substance,  also,  has  three  grades  of  oxidation,  the  oxygen  in 
the  two  last  of  which  is  in  the  ratio  of  2 to  3 ; and  the  highest  grade, 
selenic  acid,  has  in  all  its  chemical  relations  a singularly  close  ana- 
logy to  sulphuric  acid.  From  these  facts  it  is  inferred  that  selenic 
acid  is  composed  of  one  atom  of  selenium  and  three  atoms  of  oxygen. 

Oxide  of  Selenium. 

Composition. 

Form.  Selen.  Oxy.  , Equio. 

Se-j-0  39.6  or  I eq. ,+  8 or  1 eq.=47.6  Ox>de  of 

602.  This  compound  is  formed  by  heating  selenium  in  a limited 
quantity  of  atmospheric  air,  and  by  washing  the  product  to  separate 
selenious  acid,  which  is  generated  at  the  same  time.  It  is  a colour- 
less gas,  very  sparingly  soluble  in  water,  and  is  the  cause  of  the  pe» 
culiar  odour  which  is  emitted  during  the  oxidation  of  selenium. 


180 


Chlorine . 


Chap.  Ill, 


Selenious 

add. 


Decompo- 

sed. 


Selenic 

acid. 


Properties. 


Action  itpon 
metals. 


Time  or 

discovery. 

Synonyms. 


Selenious  Acid. 

Form.  Selen.  Oxy. 

.Se+20  39.6  +16  or  2 eq.=55.8 

603.  This  acid  is  prepared  by  digesting  selenium  in  nitric  or  nitro- 
hydrochloric  acid  till  it  is  completely  dissolved.  On  evaporating  the 
solution  to  dryness,  a white  residue  is  left,  which  is  selenious  acid. 
By  increase  of  temperature,  the  acid  itself  sublimes,  and  condenses 
again  unchanged  into  long  four-sided  needles.  It  attracts  moisture 
from  the  air,  and  dissolves  in  alcohol  and  water.  It  has  distinct  acid 
properties,  and  its  salts  are  called  selenites. 

604.  Selenious  acid  is  readily  decomposed  by  all  substances  which 
have  a strong  affinity  for  oxygen. 

Selenic  Acid. 

Se+30  39.6  -1-24  or  3 eq  =63.6 

605.  This  acid  is  prepared  by  fusing  nitrate  of  potassa  or  soda 
with  selenium,  a metallic  seleniuret,  or  with  selenious  acid  or  any 
of  its  salts.* 

606.  Selenic  acid  is  a colourless  liquid,  which  may  be  heated  to 
536°  without  appreciable  decomposition ; but  above  that  point  de- 
composition commences,  and  it  becomes  rapid  at  554°,  giving  rise  to 
disengagement  of  oxygen  and  selenious  acid.  When  concentrated 
by  a temperature  of  329°  its  specific  gravity  is  2.524;  at  5l2°  it  is 
2.60,  and  at  545°  it  is  2.625,  but  a little  selenious  acid  is  then 
present. 

Selenic  acid  has  a powerful  affinity  for  water,  and  emits  as  «nuch 
heat  in  uniting  with  it  as  sulphuric  acid  does.  Like  this  acid  it  is 
not  decomposed  by  hydrosulphuric  acid,  and  hence  this  gas  may 
he  employed  for  decomposing  seleniate  of  the  Oxides  of  lead  or  cop- 
per. Selenic  acid  dissolves  zinc  and  iron  with  disengagement  of 
hydrogen  gas,  and  copper  with  formation  of  selenious  acid.  It  dis- 
solves gold  also,  but  not  platinum.  Sulphurous  acid  has  no  action 
on  selenic  acid,  whereas  selenious  acid  is  easily  reduced  by  it.  Con- 
sequently, when  it  is  wished  to  precipitate  selenium  from  selenic 
acid,  it  must  be  boiled  with  hydrochloric  acid  before  sulphurous  acid 
is  added. 

Selenic  and  sulphuric  acids  are  not  only  analogous  in  composi- 
tion and  in  many  of  their  properties,  but  the  similarity  runs  through 
their  compounds  with  alkaline  substances,  their  salts  resembling 
each  other  in  chemical  properties,  constitution,  and  form.  T. 


Section  X.  Chlorine. 

Symb.  Sp.  Gr.  Chem.  Equiv. 

Cl  2.4700  Air  = t By  Vol.  100 

35.42  Hyd.  = I “ Wght.  35.42 

607.  Chlorine  was  discovered  by  Scheele  in  1774  ; it  was  called  by 
him  dephlogisticated  marine  acid.  The  term  oxy-muriatic  acid  was 
afterwards  applied  to  it  by  the  French  chemists.  From  its  colour 
the  name  by  which  it  is  now  known,  was  given  to  this  gas  by  Davy* 
from  the  Greek  /haqoq  green. 

* For  a description  of  the  process,  see  Turner’s  Elements  6th  ed.  p.  209. 


Chlorine  collected. 


l&l 

608.  Chlorine  gas  may  be  formed  by  either  of  the  following  pro-  Sect,  x. 

cesses  : Method  of 

The  most  convenient  method  ofpreparing  it  is  by  mixing  concentrated  hydro-  obtaining 
chloric  acid,  contained  in  a glass  flask  or  tubulated  retort,  with  half  its  weight  of c onne* 
finely  powdered  peroxide  of  manganese.  Effervescence,  owing  to  the  escape  of 
chlorine,  takes  place  even  in  the  cold ; but  the  gas  is  evolved  much  more  freely 
by  the  application  of  a moderate  heat.  It  should  be  collected  in  inverted  glass 
bottles  filled  with  warm  water  ; and  when  the  water  is  wholly  displaced  by  the 
gas,  the  bottles  should  be  closed  with  a well  ground  glass  stopper.  As  some  hy- 
drochloric acid  gas  commonly  passes  over  with  it,  the  chlorine  should  not  be 
considered  quite  pure,  till  after  being  transmitted  through  water. 

609.  The  theory  of  this  process  will  be  readily  understood  by  first  Theory, 
viewing  the  elements  which  act  on  each  other,  namely  : — 

Chlor.  . 70.84  or  2 eq.  2C1 

Hyd.  . 2 or  2 eq.  2H 

Hydroch.  ac.  72.84  or  2 eq.  2(H-f-Cl)j 

derived  from  them,  namely, 

Chlor.  35.42  or  1 eq. 

Oxy . lb  ^ 

Chloride  of  mang.  63.12  Water  18 

In  symbols 

Mn-j-20,  and  2(H-j-Cl),  yield  Mn-J-Cl,  2(H-f  O),  and  Cl. 

The  affinities  which  determine  these  changes  are  the  mutual  attrac- 
tion of  oxygen  and  hydrogen,  and  of  chlorine  and  manganese. 

610.  When  it  is  an  object  to  prepare  chlorine  at  the  cheapest  rate,  Cheaper 
as  for  the  purposes  of  manufacture,  the  preceding  process  is  modified  Process- 
in  the  following  manner  : — - 

Three  parts  of  sea-salt  are  intimately  mixed  with  one  of  peroxide  of  manganese, 
and  to  this  mixture  two  parts  of  sulphuric  acid,  diluted  with  an  equal  weight  of 
water,  are  added.  By  the  action  of  sulphuric  acid  on  sea-salt,  hydrochloric  acid 
is  disengaged,  which  reacts  as  in  the  former  case  upon  the  peroxide  of  manga- 
nese ; so  that,  instead  of  adding  hydrochloric  acid  directly  to  the  manganese,  the 
materials  for  forming  it  are  employed.  In  this  process,  however,  the  sulphates 
of  soda  and  protoxide  of  manganese  are  generated,  instead  of  chloride  of  manga- 
nese. 

Thus  the  materials  which  act  on  each  other  are  MnO2,  NaCl  and 
2S03 ; and  the  products  MnO,  SO3,  NaO,  SO8  and  Cl. 

611.  The  gas  should  be  received,  when  it  is  intended  to  be  kept,  Method  of 

in  bottles  filled  with,  and  inverted  in,  water  of  Fig.  157.  collecting, 

the  temperature  of  80°  or  90°  F.,  and  provided 
with  accurately  ground  stoppers.  It  will  be  found 
also  much  to  diminish  the  loss  of  gas  by  absorp^ 
tion,  if  it  be  made  to  issue  from  a gas  bottle,  the 
tube  of  which  is  sufficiently  long  to  reach  nearly 
to  the  bottom  of  the  inverted  receiving  bottle,  as 
in  Fig.  157.  The  stopper  must  be  introduced 
under  water,  while  the  bottle  remains  quite  full  of  the  gas  and  in- 
verted, and  no  water  must  be  left  in  the  bottle,  along  with  the  gas. 

Cold  recently  boiled  water,  at  the  common  pressure,  absorbs 
twice  its  volume  of  chlorine,  and  yields  it  again  when  heated. 

612.  Chlorine  is  an  elastic,  gaseous  fluid,  it  has  a pungent  disa- 
greeable odour,  and  is  highly  injurious  when  respired  even  largely  ProPerties‘ 


Mang.  . 27.7  or  1 eq.  Mn 

Oxy.  . 16  2 eq.  20 

Perox.  of  mang.  43.7  or  1 eq.  Mn-|-20 

and  then  inspecting  the  products 

Mang.  . . 27.7 

Chlor.  . . 35.42  . 


182 


Chlorine. 


Chap  HI. 


Weight. 


Destroys 

vegetable 

colours. 


Bleaching 
property  il- 
lustrated. 
Exp. 


Hydrate  of 
chlorine. 


Effect  of 
light. 


Supporter 
of  combus- 
tion. 


diluted  with  atmospheric  air.*  When  the  hand  is  immersed  in  the 
gas  a distinct  sensation  of  heat  is  perceived.  Its  colour  is  greenish 
yellow. 

According  to  Davy  100  cubic  inches  of  dry  chlorine,  at  30  Bar. 
and  60°  F.  weigh  between  76  and  77  grains.  Gay-Lussac  and 
Thenard  found  the  density  of  pure  and  dry  chlorine  to  be  2.47, 
which  gives  76.59S8  grains  as  the  weight  of  100  cubic  inches  at  60° 
F.  and  30  Bar. 

613.  Chlorine  gas,  in  its  ordinary  state,  destroys  all  vegetable 
colours.  This  may  be  shown  by  passing  into  the  gas  confined  by 
water,  a piece  of  paper  stained  with  litmus,  the  colour  of  which  will 
immediately  disappear.  Hence  the  application  of  this  gas  to  the 
purpose  of  bleaching,  its  power  of  effecting  which  may  be  shown  by 
confining,  in  the  gas,  a pattern  of  unbleached  calico,  which  has  been 
previously  boiled  in  a weak  solution  of  caustic  potassa,  and  then 
washed  in  water,  but  not  dried.  Chlorine  gas,  however,  which  has 
been  carefully  dried  by  solid  chloride  of  calcium,  and  into  which 
perfectly  dry  litmus  paper  is  introduced,  produces  no  change  of  col- 
our in  the  litmus,  a sufficient  proof  that  its  bleaching  power  depends 
on  the  presence  and  decomposition  of  waters 

614.  The  bleaching  property  may  be  shown  by  water  impregna- 
ted with  the  gas. 

For  this  purpose  fill  a small  bottle  with  cold  water,  and  invert  it  on  the  shelf 
of  the  pneumatic  trough,  pass  up  chlorine  until  about  one  half  the  water  is  dis- 
placed from  the  bottle ; close  its  mouth  with  the  thumb  under  water — agitate  the 
water  and  gas  together — invert  the  bottle  in  a basin  of  cold  water  and  remove  the 
thumb.  VVatcr  will  rush  in  to  supply  the  place  of  that  absorbed;  more  gas 
may  be  then  passed  up  and  the  process  repeated  three  or  four  times.  Strips  of  . 
calico  immersed  in  this  solution  will  soon  be  bleached. 

615.  Dry  chlorine,  is  not  condensable  by  a cold  of  — 40°  F. ; but 
either  the  moist  gas,  or  a solution  of  chlorine  in  water,  crystallizes  at 
32°.  The  crystals  may  be  obtained  by  introducing  into  a clean 
bottle  of  the  gas,  a little  water,  and  exposing  the  bottle  for  a few 
days  to  a temperature  at  or  below  freezing,  in  a dark  place.  A sol- 
id compound  of  chlorine  and  water  is  formed,  which,  in  a day  or 
two,  sublimes  and  shoots  into  delicate  prismatic  needles,  extending 
from  half  an  inch  to  two  inches  into  the  atmosphere  of  the  bottle. 

These  crystals  are  composed,  according  to  Faraday,  of  35.42  or  1 
atom  of  chlorine  + 90  or  10  atoms  water.* 

616.  Light  does  not  act  on  dry  chlorine  ; but  if  water  be  present, 
the  chlorine  decomposes  that  liquid,  unites  with  the  hydrogen  to 
form  hydrochloric  acid,  and  oxygen  gas  is  set  at  liberty.  This 
change  takes  place  quickly  in  sunshine,  more  slowly  in  diffused 
daylight,  and  not  at  all  when  light  is  wholly  excluded.  Hence  the 
necessity  of  keeping  moist  chlorine  gas,  or  its  solution,  in  a dark 
place. 

Chlorine  unites  with  some  substances  with  evolution  of  heat  and 
light,  and  is  hence  termed  a supporter  of  combustion.  If  a lighted 
taper  be  plunged  into  chlorine  gas,  it  burns  for  a short  time  with  a 


* In  case  chlorine  should  escape  into  the  apartment  and  be  inhaled,  relief  will  be 
found  by  opening  a bottle  of  aq.  ammonia  and  hreathing  over  it.  Breathing  the  vapour 
of  spirits  of  wine  or  swallowing  lumps  of  sugar  steeped  in  alcohol,  is  said  to  be  ef- 
fectual. 


Effect  of  Heat. 


183 


•o 


Fisr.  159. 


small  red  flame,  and  emits  a large  quantity  of  smoke.  Phosphorus 
takes  fire  in  it  spontaneously,  and  burns  with  a pale  white  light. 
Several  of  the  metals,  such  as  tin,  copper,  arsenic,  antimony,  and 
zinc,  when  introduced  into  chlorine  in  the  state  of  powder  or  in  fine 
leaves,  are  suddenly  inflamed.*  In  all  these  cases  the  combustible 
substances  unite  with  chlorine. 

Fill  a narrow  jar  18  or  20  inches  in  length  with  chlorine,  and  sprinkle  into  it 
powdered  antimony;  a beautiful  shower  of  the  ignited  metal  will  be  perceived 
until  the  jar  becomes  filled  with  dense  white  fumes,  which  should  as  far  as  pos- 
sible be  prevented  from  escaping  into  the  room. 

Fi?.  158. 

Put  some  mercury  into  a copper  cup,  attached  to  a thin  plate  of  cop-  >■ — - 

per,  (Fig.  158,)  and  rubbed  over  with  a little  gas-lute  to  prevent  the  met- 
als  from  combining,  and  place  it  in  a bottle  of  the  gas,  after  heating  it 
in  the  flame  of  a spirit  lamp.  It  will  take  fire  and  combine  with  the 
chlorine. 

The  most  elegant  way  of  making  these  experiments  consists  in 
introducing  the  phosphorus  or  metallic  leaves  into  a retort  furnished 
with  a stop-cock,  and  exhausted  upon  the  air-pump ; (Fig.  159.)  it  is  then  screw- 
ed into  the  cap  of  an  air  jar  of  chlorine  also  furnished  with  a stop-cock,  and 
standing  over  water  in  the  pneumatic  trough.  Upon  opening  the 
cocks  the  gas  rushes  from  the  jar  into  the  retort,  and  the  phospho- 
rus or  leaves  immediately  burn.  A small  quantity  only  of  the 
metals  should  be  used,  as  the  heat  is  sudden  and  often  sufficient 
to  crack  the  retort. 

As  retorts  are  very  liable  to  break  while  exhausting,  it  is  ad- 
visable to  cover  them  with  a cloth  during  the  process.  B.  139. 

617.  Chlorine  has  a very  powerful  attraction  for  hy- 
drogen ; and  many  of  the  chemical  phenomena,  to 
which  chlorine  gives  rise,  are  owing  to  this  property. 

A striking  example  is  its  power  of  decomposing  water 
by  the  action  of  light,  or  at  a red  heat ; and  most  com- 
pound substances,  of  which  hydrogen  is  an  element,  are 
deprived  by  it  of  that  principle.  For  the  same  reason, 
when  chlorine,  water,  and  some  other  body  which  has 
a strong  affinity  for  oxygen,  are  presented  to  one 
another,  water  is  usually  resolved  into  its  elements,  its 
hydrogen  attaching  itself  to  the  chlorine,  and  its  oxy-’ 
gen  to  the  other  body.  Hence  it  happens  that  chlorine 
is,  indirectly,  one  of  the  most  powerful  oxidizing  agents 
which  we  possess. 

618.  It  is  not  altered  by  exposure  to  very  high  terfii- 
peratures.  By  means  of  the  apparatus,  (Fig.  160,)  Davy 
exposed  it  to  the  continued  action  of  charcoal  intensely 
ignited  by  voltaic  electricity,  without  the  smallest  change 
in  its  properties. 

A glass  globe  a,  of  about  four  inches  diameter,  has  at  its  upper 
part  a sliding  wire  passing  air-tight  through  a ground  collar  b, 
to  the  lower  end  of  which  is  attached  a piece  of  well  burned 
charcoal  c : at  the  bottom  is  a stop-cock  supporting  a pair  of  brass 
pincers,  in  which  is  another  pointed  piece  of  charcoal  c;  the  globe 
is  exhausted  upon  the  air-pump,  filled  with  chlorine,  and  the  stop- 
cock d and  sliding  wire  e attached  to  the  extremities  of  the  Voltaic 
apparatus ; the  charcoal  points  are  then  brought  into  contact  by 
pushing  down  the  upper  wire,  and  they  are  thus  retained  as  long 
as  necessary  in  intense  ignition.  B, 


Sect.  X. 


Combus- 
tion of 
metals, 
Exp.  l. 

Of  mercury. 
Exp.  2. 


Exp. 


Union  wilh 
hydrogen. 


Unaltered 
in  high 
tempera- 
tures. 


Exp. 


* This  is  seen  to  most  advantage  when  a very  tall  narrow  jar  is  employed. 


184 


Chlorine  and  Hydrogen. 


Chap,  in. 

Effect  of 
pressure. 

Liquefac- 
tion of  chlo 


Used  in 
fumigation. 


Recog- 

nised. 


Exp. 


619.  When  chlorine  is  suddenly  and  considerably  condensed  by 
mechanical  pressure,  not  only  heat  is  evolved,  as  from  all  other  gas- 
es, but  it  emits  a weak  violet  coloured  light  also. 

Under  the  pressure  of  about  four  atmospheres  Faraday  discover- 
ed that  chlorine  is  a limpid  liquid  of  a bright  yellow  colour,  which 
does  not  freeze  at  the  temperature  of  zero,  and  which  assumes  the 
gaseous  form  with  the  appearance  of  ebullition  when  the  pressure  is 
removed. 

620.  Chlorine  is  useful  for  the  purposes  of  fumigation,  in  destroy- 
ing the  volatile  principles  given  off  by  putrefying  animal  matter 
and  contagious  effluvia.  A peculiar  compound  of  chlorine  and  so- 
da, the  nature  of  which  will  be  considered  in  the  section  on  sodium, 
has  been  lately  introduced  for  this  purpose  by  Labarraque. 

621.  Chlorine  is  in  general  easily  recognised  by  its  colour  and 
odour.  Chemically  it  may  be  detected  by  its  bleaching  property, 
added  to  the  circumstance  that  a solution  of  nitrate  of  oxide  of  silver 
occasions  in  it  a dense  white  precipitate  (a  compound  of  chlorine  and 
metallic  silver,)  which  becomes  dark  on  exposure  to  light. 

Into  a weak  solution  of  common  lunar  caustic,  drop  a small  quantity  of  the 
water  impregnated  with  chlorine. 

Those  compounds  of  chlorine,  which  are  not  acid,  are  termed 
chlorides  or  chlorurets. 


Muriatic 
acid  gas. 


Form. 

H+Cl 


Hydrogen  and  Chlorine — Hydrochloric  Acid. 

Composition. 

Sp.  Gr.  Chlor.  Hyd. 


Gr. 

1.2694  Air  = 1 
18.21  Hyd.  = 1 


Chlor. 
35.42  -f 


Equiv. 

By  Vol.  200 
“ Wgt.  36.42 


Explosion 
of  chlorine 


622.  When  equal  volumes  of  hydrogen  and  chlorine  gases  are 
mixed  and  exposed  to  light,  they  combine  and  produce  a sour  com- 
pound commonly  called  muriatic  acid  gas  ; or  in  conformity  to  more 
modern  nomenclature  hydrochloric  acid  gas. 

623.  Chlorine  and  hydrogen  gases  act  with  considerable  energy 
upon  each  other,  and  with  different  phenomena  accordingly  as  the 
experiment  is  conducted. 

If  a phial  be  entirely  filled  with  a mixture  of  hydrogen  and  chlorine  gases  in 

equal  proportions,  and  a well  ground  stopper  be  introduced, 'no  action  takes 

and  hydro-  place,  provided  light  be  carefully  and  completely  excluded,  even  by  standing 
Sen*  some  time  ; but  on  applying  a lighted  taper,  the  gases  immediately  explode. 

Into  a small  but  strong  vessel,  guarded  from  the  light,  introduce 
equal  volumes  of  the  two  gases,  and  inflame  the  mixture  by  the 
electric  spark,  hydrochloric  acid  gas  results.  The'  apparatus  shown 
at  Fig.  133,  may  be  used  for  the  purpose. 

The  vessel  should  be  previously  exhausted  by  the  air  pump,*  and  then  filled 
with  the  mixed  gases.  An  electric  spark  may  now  be  passed  through  the  mix- 
ture, when  a detonation  will  ensue,  to  avoid  any  injury  from  which,  the  vessel 
should  be  wrapped  in  several  folds  of  cloth.  If  the  cock,  attached  to  the  ves- 
sel, be  opened  under  mercury  in  about  a quarter  of  an  hour,  very  little  of  that 
fluid  will  enter,  proving  that  the  volume  of  gas  after  the  experiment  is  scarcely 
diminished;  that  it  is  diminished  at  all,  is  owing  to  a small  portion  of  air  being 


Exp. 


* The  foot  a being  unscrewed,  and  the  end  of  the  stop-cock  connected  with  the 
pump  plate. 


Hydrochloric  Acid . 185 

mingled  with  the  other  gases : and  it  was  found  by  Davy  that  the  more  perfectly  geet.  x. 

this  is  excluded,  the  less  is  the  amount  of  the  contraction  of  volume.  If  the 

cock  be  now  opened  under  water,  and  left  there  for  a few  minutes,  the  water 
will  be  found  to  have  ascended  and  entirely  filled  the  vessel. 

624.  If  a phial  containing  the  mixed  gases  be  exposed  to  the  Effect  of 
sun’s  rays  a detonation  will  ensue,  which  will  probably  drive  out  the  hght 
stopper.  But  if  this  should  not  happen  the  stopper  may  be  removed 
under  water,  which  will  ascend  and  completely  fill  the  phial  as  in 

the  former  experiment. 

The  agency  of  light  may  be  beautifully  shewn  by  filling  a tube  about  half  an  Exp. 
inch  diameter,  and  ] 2 inches  long,  with  the  mixed  gases,  and  alternately  shading 
it  with  an  opaque  cover,  and  exposing  it  to  the  sun’s  rays.  The  moment  the 
tube  is  exposed  even  to  the  diffused  light  of  day,  a cloudiness  will  appear  within 
it,  and  the  water  will  ascend  more  or  less  rapidly  according  to  tire  intensity  of 
the  light.  The  effect  even  of  a passing  cloud  is  distinctly  seen  in  retarding  the 
rapidity  of  the  combination,  which  is  very  striking  in  the  full  solar  light.* 

625.  The  intense  light  issuing  from  charcoal  points  connected 
with  a powerful  galvanic  battery  is  as  effectual  as  solar  light  in  act- 
ing on  hydrogen  and  chlorine  gases  ; showing  a curious  analogy 
between  electric  and  solar  light ; for  ordinary  artificial  light  does  not 
accelerate  the  combination. f 

626.  Hydrochloric  acid  gas  differs  essentially  from  either  of  its  Hydro- 
components, and  especially  in  being  instantly  absorbed  by  water.  To  chloric  acid 
preserve  it,  therefore,  in  a gaseous  state,  it  is  necessary  to  confine  it  gas‘ 

by  quicksilver. 

627.  It  was  generated  by  Faraday  in  close  tubes,  from  hydrochlo-  Liquid, 
rate  of  ammonia  and  sulphuric  acid,  in  a liquid  state,  and  its  refrac- 
tive power  was  found  inferior  to  that  of  water.  The  pressure  of  its 
vapour  at  50°  F.  was  equal  to  about  40  atmospheres. 

628.  To  obtain  hydrochloric  acid  gas  in  sufficient  quantity  for  the  proCess  for 
exhibition  of  its  properties,  the  direct  combination  of  chlorine  and  obtaining, 
hydrogen  gases  is  not  an  eligible  process.  It  maybe  procured  much 

more  conveniently  by  the  action  of  sulphuric  acid  on  sea-salt. 

Let  the  tubulated  gas  bottle,  (Fig.  87,  a,)  be  about  one  fourth  or  one  third,, 
filled  with  well  dried  sea-salt,  in  lumps,  not  in  pow^der.  To  this  adapt  the  acid 
holder,  6,  filled  with  concentrated  sulphuric  acid;  and  let  the  aperture  of 
the  bent  pipe  c,  terminate  under  a jar  filled  with,  and  inverted  in  quicksilver. 

Open  the  communication  between  the  acid  and  the  salt,  by  turning  the  cock,  d; 
and  immediately  on  the  contact  of  these  two  bodies,  an  immense  quantity  of  hy- 
drochloric acid  gas  will  be  disengaged.  A common  or  tubulated  gas-bottle,  or 
tubulated  retort  will  answer  sufficiently  well  for  procuring  the  gas.  The  first 
portions  that  come  over,  may  be  allowed  to  escape  under  a chimney  ; because 
they  are  contaminated  by  the  admixture  of  common  air  present  in  the  bottle. 

The  subsequent  portions  may  be  preserved  for  use. 

629.  This  gas  was  first  obtained  pure  by  Priestley,  but  its  compo-  *p^eory 
sition  was  discovered  by  Scheele,  and  has  since  been  most  ably  in- 
vestigated by  Davy.  Sea-salt  was  formerly  supposed  to  be  a com- 
pound of  hydrochloric  acid  and  soda  ; and,  on  this  supposition,  the 


* It  had  been  supposed  that  the  direct  beams  of  the  sun  were  necessary  to  explode  caution, 
a mixture  of  chlorine  and  hydrogen  gases  ; but  Silliman  has  related  the  accidental  ex- 
plosion of  a mixture  of  the  gases,  in  the  quantity  that  filled  a Florence  oil  flask,  not 
only  when  no  direct  solar  light  fell  upon  it,  but  when  the  diffuse  light  of  day  was  ren- 
dered more  feeble  than  common  by  a thick  snow-storm.*  This  fact  furnishes  a cau- 
tion against  mixing  the  two  gases  in  considerable  quantities, 
t Brande^  Phil.  Trans.  1820. 

* See  Amor.  Jour,  of  Sei,  iii.  342. 


186 


Chap.  III. 


Properties. 

Extin- 

guishes 

name. 

Absorbed 
by  water. 

Exp. 

Exp. 

Exp. 

Analysis. 


Chlorine  and  Hydrogen . 


soda  was  believed  merely  to  quit  the  hydrochloric  and  unite  with 
sulphuric  acid.  But  the  researches  of  Gay-Lussac,  Thenard,  and 
Davy  proved  that  it  consists  of  chlorine  and  sodium  combined  in  the 
ratio  of  their  equivalents.  The  nature  of  its  action  with  sulphuric 
acid  will  be  understood  by  comparing1  the  elements  concerned  in  the 
change  before  and  after  it  has  occurred  : — 


Hydrous  Sulp.  Acid.  Chloride  of  Sodium. 


Sulp.  of  Soda. 


Real  acid 

40.1 

Chlor. 

35.45 

Acid 

w^[oIyd: 

1 

8 

Sodium 

23.3 

Soda  £ 

40.1 

23.3 

8 


Hydrochloric  Acid. 
Chlor.  35.42 
Hyd.  1 


Or  in  symbols, 

(S+30)-f-(H-f-0),  and  Na-fCl,  yield  (Na-f 0)+(S+30),  and  H-f-Cl. 

Thus  it  appears  that  single  equivalents  of  water,  sulphuric  acid, 
and  chloride  of  sodium,  yield  sulphate  of  soda  and  hydrochloric  acid. 
The  water  of  the  sulphuric  acid  is  essential;  so  much  so,  indeed, 
that  chloride  of  sodium  is  not  decomposed  at  all  by  anhydrous  sul- 
phuric acid. 

630.  It  has  a very  pungent  smell ; and  is  sufficiently  caustic  to 
blister  the  skin,  when  applied  to  it  for  some  time.  When  brought 
into  contact  with  common  air,  it  occasions  a white  cloud,  owing  to 
its  union  with  the  aqueous  vapour,  which  is  always  present  in  the 
atmosphere.  It  is  heavier  than  common  air. 

631.  It  extinguishes  a lighted  candle.  Before  the  flame  goes  out, 
the  upper  part  of  it  assumes  a greenish  hue.  A white  vapour  also 
surrounds  the  extinguished  wick,  owing  to  the  combination  of  water, 
produced  by  the  combustion  of  the  candle,  with  the  acid  gas. 

632.  Hydrochloric  acid  gas  is  greedily  absorbed  by  water,  which 
at  40°  F.  Davy  found  to  take  up  about  480  times  its  bulk,  forming  a 
solution  of  specific  gravity  1.2109.* 

Fill  a narrow  jar,  or  tube  closed  at  one  end,  with  the  acid  gas,  over  mercury, 
and  through  the  latter  pass  up  a few  drops  of  water;  the  gas  will  be  rapidly  ab- 
sorbed, and  the  mercury  will  rise  in  the  vessel. 

The  *acid  property  of  the  solution  may  be  shown  as  follows: — 

Take  a long  tube  filled  with  the  gas  at  the  mercurial  trough,  close  it  with  the 
thumb  or  finger,  transfer  it  to  a basin  of  water  coloured  blue  by  an  infusion  of 
cabbage,  and  remove  the  finger  under  the  surface  of  the  water;  the  gas  is  imme- 
diately condensed,  the  coloured  water  is  forced  up  the  tube  by  atmospheric  pres- 
sure, and  reddened  at  the  same  time  by  the  acid  gas. 

Into  a similar  vessel  filled  with  the  gas  introduce  a piece  of  ice  ; it  will  be  li- 
quefied, almost  as  rapidly  as  if  touched  with  a red-hot  iron,  and  the  gas  will  be 
absorbed. 


The  quantity  of  real  acid  contained  in  solutions  of  different  densi- 
ties may  be  determined  by  ascertaining  the  quantity  of  pure  marble 
dissolved  by  a given  weight  of  each.  Every  50.6  grains  of  marble 
correspond  to  36.42  of  real  acid. 

633.  When  a mixture  of  oxygen  and  hydrochloric  acid  gases  is 
either  electrified  or  transmitted  through  a red-hot  porcelain  tube,  the 
oxygen  unites  with  the  hydrogen  of  the  acid,  and  the  chlorine  of 
the  latter  is  set  at  liberty.  A similar  mixture  Henry  found  to  be 
also  decomposed  by  being  exposed,  at  a temperature  of  250°  F.  to 


* Elements , p.  252.  For  table  of  specific  gravity  of  acid  of  different  strengths,  see 
Appendix. 


187 


Liquid  Hydrochloric  Acid . 

contact  with  the  platinum  sponge.  Water  is  formed  and  the  disen- 
gaged chlorine  acts  on  the  mercury  used  to  confine  the  gas.^ 
H.  1-  268. 

634.  It  is  in  the  state  of  watery  combination  that  hydrochloric  acid 
is  kept  for  chemical  purposes,  and  all  the  processes  for  preparing  the 
liquid  acid  have  for  their  object  the  disengagement  of  the  acid  gas, 
and  its  absorption  by  water. 

For  saturating  water  with  this  gas  we  commonly  employ  Woulfe’s 
apparatus.! 

The  retort  being  furnished  with  the  bent  tube,  a,  Fig.  161,  and  placed  in  asand 
bath,  the  junctures  should  be  carefully  luted,  and  the  acid  should  be  added  to  the 
salt  in  the  retort  at  intervals.  The  water  employed  may  amount  to  half  the 
weight  of  the  salt,  and  may  be  equally  distributed  between  the  bottles.  These  it 


* Phil.  Trans.  1824. 

t In  several  instances,  the  substance  raised  by  distill&tion  is  partly  a condensable  li- 
quid, and  partly  a gas,  which  is  not  condensed,  till  it  is  brought  into  contact  with  water. 
To  effect  this  double  purpose,  a series  of  receivers,  termed  Woulfe’s  apparatus,  is 
" employed.  The  first  receiver  (a,  Fig.  161)  has  a right-angled  glass  tube,  open  at  both 


Fig.  161. 


ends,  fixed  into  its  tubulure  ; and  the  other  extremity  of  the  tube  is  made  to  terminate- 
beneath  the  surface  of  distilled  water,  contained,  as  high  as  the  horizontal  dotted  line,, 
in  the  three-necked  bottle  c.  From  another  neck  of  this  bottle,  a second  pipe  proceeds, 
which  ends,  like  the  first,  under  water,  contained  in  a second  bottle  d.  To  the  centra! 
neck,  a straight  tube  open  at  both  ends,  is  fixed,  so  that  its  lower  end  may  be  a little- 
beneath  the  surface  of  the  liquid.  Of  these  bottles  any  number  may  be  employed  that 
is  thought  necessary. 

The  materials  being  introduced  into  the  retort,  the  arrangement  completed,  and  tlie 
joints  secured,  the  distillation  is  begun.  The  condensable  vapour  collects  in  a liquid 
form  in  the  balloon  b,  while  the  evolved  gas  passes  through  the  bent  pipe,  beneath  the 
surface  of  the  water  in  c,  which  continues  to  absorb  it  till  saturated.  When  the  water 
of  the  first  bottle  can  absorb  no  more,  the  gas  passes,  uncondensed,  through  the-second 
right-angled  tube,  into  the  water  of  the  second  bottle,  which,  in  its  turn,  becomes  satu- 
rated. Any  gas  that  maybe  produced,  which  is  nojt  absorbable  by  water,  escapes 
through  the  bent  tube  e,  and  may  be  collected,  if  necessary. 

Supposing  the  bottles  to  be  destitute  of  the  middle  necks,  and,  consequently,  without 
the  perpendicular  tubes,  the  process  would  be  liable  to  be  interrupted  by  an  accident: 
for  if,  in  consequence  of  a diminished  temperature,  an  absorption  or  condensation  of 
gas  should  take  place  in  the  retort,  and,  of  course,  in  the  balloon  b,  it  must  necessarily 
ensue  that  the  water  of  the  bottles  c and  d would  be  forced,  by  the  pressure  of  the  at- 
mosphere into  the  balloon,  and  possibly  into  the  retort ; but  with  the  addition  of  the 
central  tubes,  a sufficient  quantity  of  air  rushes  through  them  to  supply  any  accidental 
vacuum.  This  inconvenience,  however,  is  still  more  conveniently  obviated  by  Wel- 
ther’s  tube  of  safety,  e,  which  supersedes  the  expediency  of  three-necked  bottles.  The 
apparatus  being  adjusted,  as  shown  by  the  figure,  a small  quantity  of  water  is  poured 
into  the  funnel,  so  as  to  about  half  fill  the  hall  d.  When  any  absorption  happens,  the 
fluid  rises  in  the  hall,  till  none  remains  in  the  tube,  when  a quantity  of  air  immediately 
rushes  in.  On  the  other  hand,  no  gas  can  escape,  because  any  pressure  from  within  is 
instantly  followed  by  the  formation  of  a high  column  of  liquid  in  the  perpendicular 
part,  which  resists  the  egress  of  gas. — A convenient  apparatus  for  this  and  similar 
purposes  is  described  in  Brewster’s  Edin.  Jour,  viii-  p.  3. 


Sect.  X. 


Liquid  hy- 
drochloric 
acid,  how 
obtained. 


Woulfe'a  appa- 
ratus, 


188 


Chap.  Ill, 


Impurities. 


Properties 
of  the 
liquid  acid. 


Combines 
with  alka- 
lies. 

Aqua  regia. 


Chlorine  and  Hydrogen. 

is  better  to  surround  with  cold  water,  or,  still  preferably,  with  ice  or  snow  ; be- 
cause the  condensation  of  the  gas  evolves  considerable  heat,  which  prevents  the 
water  from  attaining  its  full  impregnation.  When  the  whole  of  the  sulphurio 
acid  has  been  added,  and  the  gas  no  longer  issues,  let  a fire  be  lighted  in  the  fur- 
nace beneath  the  sand  bath,  removing  the  bent  tube  a,  and  substituting  a well 
ground  glass  stopper.  This  will  renew  the  production  of  gas  ; and  the  tempera- 
ture must  be  preserved,  as  long  as  gas  continues  to  be  evolved.  At  this  period  it 
is  necessary  to  keep  the  luting  which  connects  the  retort  and  receiver,  perfectly 
cool.*  Towards  the  close  of  the  process,  a dark  coloured  liquid  is  condensed  in 
the  first  receiver,  consisting  of  a mixture  of  sulphuric  and  hydrochloric  acids. 
When  nothing  more  comes  over,  the  operation  may  be  suspended,  and  the  liquid 
in  the  two  receivers  must  be  preserved  in  bottles  with  ground  stoppers.  It  con- 
sists of  liquid  hydrochloric  acid.  H.  272. 

635.  When  hydrochloric  acid  is  thus  dissolved  in  water,  it  forms 
the  liquid  muriatic  acid , or  spirit  of  salt.  When  pure  it  is  perfectly 
colourless,  but  it  is  generally  impure.  Its  usual  impurities  are  nitric 
acid,  sulphuric  acid,  and  oxide  of  iron.  The  presence  of  nitric  acid 
may  be  inferred  if  the  hydrochloric  acid  has  the  property  of  dissolv- 
ing gold-leaf.  Iron  may  be  detected  by  ferrocyanuret  of  potassium, 
and  sulphuric  acid  by  chloride  of  barium,  the  suspected  hydrochloric 
acid  being  previously  diluted  with  three  or  four  parts  of  water.  The 
presence  of  nitric  acid  is  provided  against  by  igniting  the  sea-salt, 
in  order  to  decompose  any  nitre  which  it  may  contain.  The  other 
impurities  may  be  avoided  by  employing  YVoulfe’s  apparatus. 

636.  Liquid  hydrochloric  acid  emits  white  suffocating  fumes,  con- 
sisting of  hydrochloric  acid  gas,  which  become  visible  by  contact  with 
the  moisture  of  the  air  (630).  When  heated  in  a retort,  the  gas  is 
disengaged,  and  may  be  collected.  It  is  not  decomposed  by  the 
contact  of  charcoal,  or  other  combustible  bodies.  When  diluted  with 
water,  an  elevation  of  temperature  is  produced,  less  remarkable, 
however,  than  that  occasioned  by  diluting  sulphuric  acid  (66) ; and 
when  the  mixture  has  cooled  to  its  former  temperature,  a diminution 
of  volume  is  found  to  have  ensued. 

637.  Hydrochloric  acid  combines  readily  with  alkalies,  and  with 
most  of  the  oxides  both  in  their  pure  and  carbonated  state.!  H.  i.  272. 

A mixture  of  nitric  and  hydrochloric  acids,  in  the  ratio  of  one 
measure  of  the  former  to  two  of  the  latter,  has  long  been  known 
under  the  name  of  aqua  regia , as  a solvent  for  gold  and  platinum. 
When  these  acids  are  mixed  together,  the  solution  instantly  becomes 
yellow;  and  on  heating  the  mixture,  pure  chlorine  is  evolved,  and 
the  colour  of  the  solution  deepens.  On  continuing  the  heat,  chlorine 
and  nitrous  acid  vapors  are  disengaged.  At  length  the  evolution  of 
chlorine  ceases,  and  the  residual  liquid  is  found  to  be  a solution  of 
hydrochloric  and  nitrous  acids,  which  is  incapable  of  dissolving 
gold.  The  explanation  of  these  facts  is,  that  nitric  and  hydrochloric 
acids  decompose  one  another,  giving  rise  to  the  production  of  water 
and  nitrous  acid,  and  the  separation  of  chlorine;  while  hydrochloric 
and  nitrous  acids  may  be  heated  together  without  mutual  decompo- 


* The  clay  and  sand  lute  is  the  best  for  this  juncture. 

+ For  a full  account  of  the  opinions  which  have  been  maintained  concerning  the 
nature  of  chlorine  and  hydrochloric  acid,  the  reader  is  referred  to  the  controversy  be- 
tween Murray  and  J.  Davy,  in  the  34lh  vol.  of  Richoi son's  Jour.  \ to  Davy’s  paper  in 
the  Phil.  Trans,  for  ISIS.  p.  169  ; to  the  Sth  vol.  of  Trans.  Roy.  Soc.  Edin.  ; the  Ann. 
of  Philos,  xii.  379  and  xiii.  26,  285  ; and  to  a paper  by  Phillips,  in  the  new  series  of 
that  work.  vol.  i.  p.  27,  on  the  action  of  chlorides  on  water. 


189 


Chlorine  and  Oxygen. 

sition.  It  is  hence  inferred  that  the  power  of  nitro-hydrochloric  acid  Sect,  x. 
in  dissolving  gold  is  owing  to  the  chlorine  which  is  liberated.^ 

638.  Hydrochloric  acid  is  distinguished  by  its  odour,  volatility,  Hydrochlo- 
and  strong  acid  properties.  With  nitrate  of  oxide  of  silver  it  yields  ricaciddis- 
the  same  precipitate  as  chlorine;  but  there  is  no  difficulty  in  dis- tinSuistle^- 
languishing  between  them  ; for  the  bleaching  property  of  the  former 

is  a sure  ground  of  distinction. 

639.  The  experiments  of  Davy,  and  Gay-Lussac  and  Thenard  Composi- 
concur  in  proving  that  hydrogen  and  chlorine  gases  unite  in  equal  tion. 
volumes,  and  that  the  hydrochloric  acid,  which  is  the  sole  and  con- 
stant product,  occupies  the  same  space  as  the  gases  from  which  it 

is  formed.  From  these  facts  the  composition  of  hydrochloric  acid 
is  easily  inferred.  For,  as 

50  cubic  inches  of  chlorine  weigh  . . 38.2994  grains, 

50  “ hydrogen  . . 1.0683  “ 

100  cubic  inches  of  hydrochloric  acid  gas  must  weigh  39.3677 

These  numbers  are  nearly  in  the  ratio  of  1 to  35.42,  being  that  of 
single  eq.  of  chlorine  and  hydrogen.  Hence  its  eq.  is  as  already 
stated. 

Compounds  of  Chlorine  and  Oxygen , 

640.  The  leading  character  of  these  compounds  is  derived  from  Leading 
the  circumstance  that  chlorine  and  oxygen,  the  attraction  of  which  character- 
for  most  elementary  substances  is  so  energetic,  have  but  a feeble 
affinity  for  each  other. 

They  cannot  be  made  to  combine  directly,  and  very  slight  causes 
effect  their  separation. 

Two  volumes  of  chlorine,  as  also  two  of  hydrogen  and  of  nitro- 
gen correspond  to  one  equivalent  or  atom.! 

Hypocklorous  Acid. 

Composition. 

Form,  Sp,  Gr,  Chlor.  Oxy.  Ckem.  Equiv. 

CHO,  Cl,  or  CIO  3.0212  Bv  Wght.  35.42  = 8 43.42 

“ Vol.  2 = 1 

641.  This  gas  was  discovered  in  1811  by  Davy  and  describ-  Discovery, 
ed  under  the  name  of  EuchlorineX  Until  recently  it  has  been  con- 
sidered to  be  the  protoxide  of  chlorine. 

642.  It  is  obtained  by  the  action  of  hydrochloric  acid  on  chlorate  Process, 
of  potassa. 

Twelve  parts  of  acid  diluted  with  an  equal  weight  of  water  may  be  poured 
upon  five  parts  of  the  salt  (50  or  100  grains  will  be  sufficient);  a very  gentle 
heat  is  to  be  applied  by  a small  spirit  lamp,  and  the  gas  may  be  collected  over 
mercury. 

643.  This  gas  is  generally,  if  not  always,  best  made  in  a tube  retort,  formed 
from  a piece  of  plain  glass  tube,  about  half  an  inch  in  diameter,  two  or  three 

* Davy  in  Quart . Jour.  vol.  1. 

+ Berzelius  considers  the  atoms  of  all  elements  as  possessing  the  same  vo’ume, 
and  regards  the  compounds  of  chlorine  and  oxygen  as  composed  of  two  equiv.  of 
chlorine  and  one,  four,  five  and  seven  of  oxygen. 

t Philos . Trans. 


190 

Chap.  III. 


Caution. 


Theory. 


Chlorine  and  Oxygen. 


inches  in  length,  according  to  circumstances,  and  closed  at  one 
~ end.  (Fig.  102.)  The  mouth  should  be  fitted  with  a good  perfora- 
ted cork,  having  a small  tube  fixed  into  it,  which,  after  proceed- 
ing about  an  inch  upwards  from  the  cork,  is  to  turn  on  nearly 
at  right  angles  for  about  three  inches,  and  then  return  to  its  first 
direction  for  about  the  eighth  of  an  inch.  This  piece  of  tube 
is  the  neck  of  the  retort,  whilst  the  wide  short  piece  is  the 

body  ; the  latter  having  received  its  charge,  the  cork  is  to  be  __ 

put  in  and  made  tight  by  cement,  when  the  distillation  may  be  proceeded  with, 
and  the  gas  evolved  and  collected.  F. 

Great  care  should  be  taken  in  preparing  this  gas,  as  it  explodes 
violently  when  exposed  to  a moderate  heat,  though  nothing  is  mixed 
with  it ; when  the  spirit  lamp  is  used,  it  should  be  held  immediately 
below  the  retort,  so  as  not  to  play  on  its  sides,  and  the  gas  should 
then  come  slowly  away,  producing  a very  moderate  effervescence.* 

644.  When  the  object  is  merely  to  notice  a few  F*s- 163- 
of  the  properties  of  the  gas,  it  may  be  obtained 
from  materials  placed  in  a glass  tube,  15  or  16 
inches  in  length  and  about  an  inch  in  diameter,  sur- 
rounded by  water  and  heated,  as  in  the  Fig.  163. 

645.  The  production  of  this  gas  is  explicable  by 
the  fact,  that  hydrochloric  and  chloric  acids  mutual- 
ly decompose  each  other.  When  hydrochloric  acid 
and  chlorate  of  potassa  are  mixed  together,  more  or  less  of  the  po- 
tassa  is  separated  by  the  hydrochloric  acid  from  the  chloric  acid,  and 
the  latter  being  set  at  liberty,  reacts  on  free  hydrochloric  acid.  The 
result  depends  upon  the  relative  quantities  of  the  materials.  If  hy- 
drochloric acid  be  in  excess,  the  chloric  acid  undergoes  complete  de- 
composition. For  each  eq.  of  chloric  acid,  five  eq.  of  hydrochloric 
acid  are  decomposed : the  five  eq.  of  oxygen  contained  in  the 
former,  unite  with  the  hydrogen  of  the  latter,  producing  five  eq. 
of  water ; while  the  chlorine  of  both  acids  is  disengaged.  If,  on 
the  contrary,  chlorate  of  potassa  be  in  excess,  the  chloric  acid  is  de- 
prived of  part  of  its  oxygen  only  ; the  products  are  water  and  the 
euchlorine  of  Davy. 

646.  The  chloric  and  hydrochloric  acids  react  on  each  other  in 
the  ratio  of  one  eq.  to  two,  or,  what  is  the  same  thing,  in  that  of 
four  eq.  to  eight  eq. ; thus 

4 (Cl+50)  . u 8 (H+O) 

and  8 (H  +C1 ) yleld  12  (Cl+O) 


* In  reference  to  the  distillation  of  this  gas,  and  of  all  other  explosive  substances, 
the  student  should  be  aware  of  the  caution  required  to  prevent  accidents,  in  case  explo- 
sion should  occur.  Whenever  such  an  effect  is  probable,  the  vessel  should  be  sur- 
rounded with  low  or  cloth,  that  if  it  break,  the  fragments  may  be  retained  ; and  during 
distillation  the  side  of  the  apparatus,  or  that  part  which  is  guarded  by  the  tow,  is  to  be 
turned  towards  the  eyes,  that  they  at  least  may  be  out  of  danger.  It  is  not  easy  to 
wrap  tow  regularly  and  tightly  round  a clean  glass  tube,  from  its  tendency  to  slip  over 
the  surface ; but  the  difficulty  is  easily  obviated,  by  rubbing  the  outside  of  the  tube 
with  soft  cement,  or  a very  little  turpentine  with  a piece  of  tow  or  cloth,  so  as  to  ren- 
der it  slightly  adhesive  to  the  fingers.  Faraday  p.  409. 

Silliman  prefers  placing  the  materials  for  producing  the  gas  in  a small  glass  flask 
furnished  with  a tube  bent  twice  at  right  angles,  and  passing  to  the  bottom  of  any 
clean  dry  phial,  flask,  or  tube,  rather  deep  with  a narrow  neck,  a gentle  heat,  applied 
beneath  the  flask,  soon  disengages  the  euchlorine  gas,  which,  by  its  great  weight,  dis- 
places the  common  air  from  the  recipient,  and  takes  its  place.  By  using  tongs,  pro- 
perly curved,  so  as  to  embrace  the  phials  or  tubes  filled  with  the  gas,  the  operator  may 
perform  all  the  necessary  experiments,  without  danger  of  causing  an  explosion  by  the 
warmth  of  the  hand.  Amer.  Jour.  vi.  165. 


Chlorous  Acid . 


191 


The  gas  thus  obtained,  is  not  a distinct  compound,  but  a mixture  Sect,  x. 
of  chlorine  and  chlorous  acid.  T.  218. 

647.  The  process  for  obtaining  the  pure  acid,  is  to  pour  into  bot-  Process  for 
ties  filled  with  chlorine  gas,  peroxide  of  mercury  in  fine  powder,  and  ^dpure 
mixed  with  twice  its  weight  of  distilled  water ; by  brisk  agitation 

the  chlorine  is  rapidly  and  completely  absorbed,  if  a slight  excess  of 
the  peroxide  be  used.  By  this  process  one  portion  of  the  peroxide 
of  mercury,  HgO2,  is  decomposed,  both  its  constituents  combining 
with  chlorine ; the  mercury  forming  corrosive  sublimate  HgCl2,  and 
the  oxygen  hypochlorous  acid.  The  latter  remains  in  solution  in 
the  water  ; while  the  former,  by  combining  with  undecomposed  per- 
oxide of  mercury,  forms  the  sparingly  soluble  oxychlUride  of  mer- 
cury, which  is  separated  by  filtration.  The  hypochlorous  acid  being 
volatile,  is  obtained  pure  by  distillation  ; the  temperature  being  kept 
below  212°  as  the  acid  decomposes  at  that  heat.  The  process  is 
best  performed  under  reduced  pressure. 

648.  As  thus  obtained,  hypochlorous  acid  is  a transparent  liquid  properties, 
of  a slightly  yellow  colour  ; when  concentrated,  with  a strong  pene- 
trating odour,  similar  to  that  of  chlorine.  It  acts  powerfully  upon  the 

skin,  and  bleaches. 

It  is  easily  decomposed,  chlorine  being  evolved  and  chloric  acid 
produced  ; a change  effected  by  light  and  instantly  by  the  direct 
rays  of  the  sun.  It  is  also  decomposed  by  angular  bodies,  as  by 
pounded  glass. 

649.  It  is  one  of  the  most  powerful  oxidizing  agents  ; its  action,  Oxidizes, 
however,  is  various  and  is  principally  observed  in  relation  to  the  sim- 
ple non-metallic  elements.  Its  action  on  the  more  perfect  metals  is 
slight,  with  the  exception  of  iron  and  silver,  which  in  a state  of  mi- 
nute division  instantly  decompose  it. 

650.  Hypochlorous  acid  has  also  been  obtained  in  the  gaseous  Another 
form,  by  introducing  a small  quantity  of  its  concentrated  solution  process, 
into  a bell  glass  over  mercury  and  adding  fragments  of  dry  nitrate 

of  lime.  The  latter  unites  with  the  water  and  the  acid  gas  escapes. 

The  gas  is  of  a yellowish  green  colour  ; it  unites  rapidly  with  water 
which  absorbs  at  least  100  times  its  volume. 

651.  It  detonates  by  a slight  increase  of  temperature,  and  oxygen  Specific 
and  chlorine  are  the  results  ; 100  measures  produce  100  of  chlorine  gravitYj&c- 
and  50  of  oxygen.^  From  these  data  its  sp.  gr.  is  3.0212  ; its  eq. 

43.42  ; eq.  vol.  ==  100 ; symb.  Cl+O,  Cl,  or  CIO.  (T.) 

Chlorous  Acid. 

Composition. 

Chi.  Oxy.  Equiv.  Equiv.  Vol. 

Bv  Wght.  35.42  32  67.42  = 200 

“ Vol.  2 4 

652.  This  compound  was  discovered  by  Davy  in  1815,  and  soon 
after  by  Count  Stadion  of  Vienna.  It  has  heretofore  been  described 
as  the  peroxide  of  chlorine , but  having  been  found  to  possess  acid 
properties,  and  to  form  definite  compounds  with  alkaline  bases,  it 


Symb.  Sp.  Gr. 

Cl+40,  Cl  or  CIO4  2.3374 


* Balard  Ann.  de  Chim.  et  de  Phys.  lvii.  225. 


192 


Chap.  111. 


Method  of 
obtaining. 


Theory. 


Salts  of, 


Decompo- 
sed by 
phosphorus 
and  neat. 


Process. 


Properties. 


Decompos- 

ed. 


* 

Chlorine  and  Oxygen. 

must  now  be  called  chlorous  acid.  It  is  formed  by  the  action  of  sul- 
phuric acid  on  the  chlorate  of  potassa. 

To  procure  it,  50  or  60  grains  of  the  powdered  chlorate  of  potassa,  are  to 
be  mixed  with  a small  quantity  of  concentrated  sulphuric  acid.  When  thor- 
oughly incorporated,  a solid  mass  will  result,  of  a bright  orange  colour.  This  is 
to  be  introduced  into  a very  small  retort  of  glass,  or  a bent  tube,  which  hs  to  be 
exposed  to  the  heat  of  water  gradually  warmed,  but  prevented  from  attaining 
the  boiling  point,  by  an  admixture  of  spirit  of  wine. 

653.  In  this  process  the  sulphuric  acid  decomposes  some  of  the 
chlorate  of  potassa,  and  sets  chloric  acid  at  liberty.  The  chloric 
acid  at  the  moment  of  separation,  resolves  itself  into  chlorous  acid  and 
oxygen  ; the  last  of  which,  instead  of  escaping  as  free  oxygen  gas, 
goes  over  to  the  acid  of  some  undecomposed  chlorate  of  potassa,  and 
converts  it  into  perchloric  acid.  The  products  are  bisulphate  and 
perchlorate  of  potassa,  and  chlorous  acid.  It  is  probable  that  every 
three  eq.  of  chloric  acid  yield  one  eq.  of  perchloric  and  two  eq.  of 
chlorous  acid.  T. 

654.  This  acid  readily  unites  with  the  alkalies  and  alkaline  earths, 
and  the  union  is  effected  by  transmitting  the  gas  into  the  alkaline 
solutions.  The  salts  are  soluble  in  water  and  bleach. 

655.  It  is  decomposed,  at  common  temperatures,  by  phosphorus, 
which  occasions  an  explosion  when  introduced  into  it.  It  explodes 
violently  at  212°,  and  great  care  is  necessary  in  operating  with  it. 

Chloric  Acid. 

Composition. 

Chlor.  Ory.  Equit. 

By  Wght.  35.42  40  75.42 

“ Vol.  2 5 

656.  When  a current  of  chlorine  gas  is  passed  into  a strong  solu- 
tion of  pure  potassa,  part  of  the  alkali  is  decomposed  and  chloride  of 
potassium  and  hypochlorite  of  potassa  are  generated.  On  bringing 
the  solution  to  the  boiling  point,  the  latter  salt  is  decomposed.  The 
changes  are  complicated  ; from  experiments*  nine  eq.  of  hypochlo- 
rite of  potassa  produce  one  eq.  of  chlorate  of  potassa,  eight  eq.  of 
chloride  of  potassium,  and  twelve  eq.  of  oxygen  : or  thus 

9 (KO+CIO)  yield  (KO+CIO*),  8KC1  and  120 

657.  When  weak  sulphuric  acid  is  added  to  a dilute  solution  of 
chlorate  of  baryta,  exactly  sufficient  for  combining  with  the  baryta, 
sulphate  of  baryta  subsides,  and  pure  chloric  acid  remains  in  the 
liquid. 

658.  This  acid  was  first  obtained  by  Gay-Lussac.  It  reddens 
vegetable  blue  colours,  has  a sour  taste,  and  forms  neutral  salts,  cal- 
led chlorates  (formerly  hy per oxy muriates.)  It  has  no  bleaching  prop- 
erties, nor  does  it  afford  a precipitate  with  solution  of  nitrate  of  oxide 
of  silver. 

659.  Chloric  acid  is  easily  decomposed  by  oxidizing  agents  ; and 
it  is  easily  known  by  forming  a salt  with  potassa,  which  crystallizes 


fbrm. 

01+50,01,’  or  C105 


* Of  Morin,  Soubeirain.  and  Balard. 


193 


Chlorine  and  Nitrogen . 

in  tables  and  has  a pearly  lustre,  deflagrates  on  burning  coals,  and  Sect,  x. 
yields  chlorous  acid  by  the  action  of  concentrated  sulphuric  acid. 

Perchloric  Acid. 

Composition. 

Form.  Chi.  Oxy.  Equiv. 

CI+70,  Cl  or  ClOr  By  Wght.  35.42  . 56  91.42 

“ Vol.  2 7 

660.  The  saline  matter  which  remains  in  the  retort  after  forming  process 
chlorous  acid,  is  a mixture  of  perchlorate  and  bisulphate  of  potassa, 

and  by  washing  it  with  cold  water,  the  bisulphate  is  dissolved  and 
the  perchlorate  is  left.  This  acid  may  be  prepared  from  the  salt  by 
mixing  it  in  a retort  with  half  its  weight  of  sulphuric  acid,  diluted 
with  one  third  water,  and  applying  heat  to  the  mixture.  At  the 
temperature  of  about  284°  F.  white  vapours  rise,  which  condense  as 
a colourless  liquid  in  the  receiver.  This  is  a solution  of  perchloric 
acid. 

Stadion,  its  discoverer,  found  it  to  be  a compound  of  1 eq.  chlo-  Composi- 
rine  -f-  7 eq.  oxygen,  and  his  analysis  has  been  confirmed  by  Gray- tion- 
Lussac  and  others. 

661.  When  concentrated  it  has  a density  of  1.65  in  which  state  it  Properties, 
emits  vapour  on  exposure  to  the  air,  absorbs  moisture,  and  boils  at 

392°.  It  hisses  when  thrown  into  water  like  a red-hot  iron  when 
quenched. 

662.  It  forms  a salt  with  potassa,  requiring  65  times  its  weight 
of  water  at  60°  for  solution.  The  perchlorate  of  potassa  is  dis® 
tinguished  from  the  chlorate  by  not  acquiring  a yellow  tint  on  the 
addition  of  hydrochloric  acid. 

Quadrochloride  of  Nitrogen — Chloride  of  Nitrogen » 

Sp.  Gr.  1,653. 

663.  Quadrochloride  of  nitrogen,  discovered  in  1811  by  Dulong,*  Properties, 
is  one  of  the  most  explosive  compounds  yet  known,  having  been  the 

cause  of  serious  accidents  both  to  its  discoverer  and  to  Davy.f  It 
does  not  congeal  in  the  intense  cold  produced  by  a mixture  of  snow 
and  salt.  It  may  be  distilled  at  160°  ,;  but  at  a temperature  between 
200  and  212°  it  explodes.  Its  mere  contact  with  some  substances  of 
a combustible  nature  causes  detonation  even  at  common  temperatures. 

This  result  ensues  particularly  with  oils,  both  volatile  and  fixed. 

The  products  of  the  explosion  are  chlorine  and  nitrogen. £ 

664.  It  is  prepared  by  inverting  a jar  or  wide-mouthed  bottle,  (capable  of  con-  process> 
taining  about  12  or  14  ounces)  full  of  chlorine,  over  a dilute  solution  of  the  hy- 
drochlorate of  ammonia,  (sal  ammoniac)  made  by  dissolving  an  ounce  of  the  salt  in 

10  or  12  ounces  of  water ; the  bottle  is  placed  on  a very  strong  shallow  leaden 
cup,  which  rests  on  a deep  plate  containing  the  solution  previously  heated  to  the 
temperature  of  90°.  One  portion  of  the  chlorine  takes  the  hydrogen  of  the  ammo- 
nia,§ forming  hydrochloric  acid,  and  the  other,  combining  with  the  nitrogen,  is 
converted  into  the  quadrochloride,  which  collects  in  the  form  of  an  oil  on  the 
surface  of  the  liquid,  and  drops  through  it  into  the  leaden  cup  : an  additional 
quantity  of  the  solution  must  be  ready  to  fill  up  the  plate  as  the  absorption  of  the 
chlorine  proceeds. 

665.  Great  care  must  be  taken  not  to  shake  the  bottle,  and  any  Caution. 

* Ann.  de  Ch.  Ixxxvi.  t Phil.  Trans.  1813. 

} Nicholson’s  Jour,  xxxiv.  § Ammonia  consists  of  hydrogen  and  nitrogen. 

25 


194 


Chlorine  and  Carbon. 


ChaP-  greasy  or  oily  matter  adhering  to  it  must  be  removed  by  washing  it 
with  a dilute  solution  of  potassa  before  it  is  filled  with  chlorine. 
When  the  oil  has  fallen  into  the  leaden  cup,  the  bottle  is  carefully 
moved  from  the  cup  to  the  plate,  and  the  leaden  cup  taken  cautiously 
away. 

The  liquid  remaining  above  the  quadrochloride  in  the  cup  is  with- 
drawn by  dipping  small  pieces  of  filtering  paper  into  it.  The  oily 
looking  globules  may  be  conveniently  removed  by  drawing  Fig.  164. 
them  into  a small  and  perfectly  clean  glass  syringe,  made 
of  a glass  tube  drawn  to  a pointed  orifice,  and  having  a cop- 
per wire  with  a piece  of  clean  tow  wrapped  round  it  for  a 
piston,  (Fig.  164) ; in  this  way  a globule  may  be  drawn 
into  the  tube,  and  transferred  to  any  other  vessel. 

Precautions  666.  In  making  these  experiments,  a small  globule  of 
in  “xperi-  the  compound,  about  the  size  of  a mustard-seed,  should  be 
menting  cautiously  transferred  to  a clean  porcelain  basin,  half  filled 
with  water.  The  basin  should  be  covered  with  a wire  safe- 
guard. A very  small  piece  of  phosphorus,  fixed  to  the  end 
of  a long  rod  with  the  extremity  dipped  in  oil,  may  be  then 
brought  into  contact  with  the  globule,  which  instantly  explodes,  dis- 
persing the  water  and  breaking  the  basin.  The  same  compound  may 
be  obtained  by  suspending  a fragment  of  sal  ammoniac  in  a solution 
of  hypochlorous  acid.  T. 

Analysis.  667.  Davy  analyzed  this  compound  by  means  of  mercury,  which 
unites  with  chlorine,  and  liberates  the  nitrogen.  He  inferred  from 
his  analysis  that  its  elements  are  united  in  the  proportion  of  four 
measures  of  chlorine  to  one  of  nitrogen ; and  it  hence  follows  that, 
by  weight,  it  consists  of  four  equivalents  of  chlorine,  and  one  equi- 
valent of  nitrogen.  Its  odour  is  extremely  penetrating  and  almost 
insupportable,  affecting  the  eyes  very  much  on  leaning  over  it  even 
for  a second  or  two.  It  is  very  volatile. 

Per  chloride  of  Carbon. 

Symb.  Equiv. 

2C+3C1,  or  C^t8.  1 IS. 5 

Discovery  668 . The  discovery  of  this  compound  is  due  to  Faraday.  When 

olefiant  gas  (a  compound  of  carbon  and  hydrogen)  is  mixed  with 
chlorine,  combination  takes  place  between  them,  and  an  oil-like 
liquid  is  generated,  which  consists  of  chlorine,  carbon  and  hydrogen. 
On  exposing  this  liquid  in  a vessel  full  of  chlorine  gas  to  the  direct 
solar  rays,  the  chlorine  acts  upon  and  decomposes  the  liquid,  hydro- 
chloric acid  is  set  free,  and  the  carbon,  at  the  moment  of  separation, 
unites  with  the  chlorine.* 

p . 669.  Perchloride  of  carbon  is  solid  at  common  temperatures,  has  an 

roper  ies.  aromatjc  0(j0ur  approaching  to  that  of  camphor,  is  a non-conductor 
of  electricity,  and  refracts  light  very  powerfully.  Its  specific  gravity 
is  exactly  double  that  of  water.  It  fuses  at  320°,  and  after  fusion 
it  is  colourless  and  very  transparent.  It  boils  at  360°. 

Perchloride  of  carbon  burns  with  a red  light  when  held  in  the 
flame  of  a spirit-lamp,  giving  out  acid  vapours  and  smoke. t 

* Phil.  Trans.  1821. 

t Protochloride  of  Carbon.  Symb.  C-f-Cl,  or  CC1.  Equiv.  41.64  Discovered 
by  Faraday  in  decomposing  perchloride  of  carbon.  It  is  liquid,  colourless,  and  boils 


195 


Nature  of  Chlorine. 


670.  Chlorine  was  long  regarded  as  a compound  of  muriatic  acid  Sect,  x. 
and  oxygen,  an  opinion  ably  defended  by  Murray  : the  phenomena  Nature  of 
which  it  presents  are  all  explicable  on  this  supposition,  though  the  chlorine, 
view  proposed  by  Davy,  Gay-Lussac  and  Thenard,  of  its  elementary 
nature,  is  considered  more  in  accordance  with  actual  experiment, 
and  now  generally  adopted.^ 

at  170°.  Its  density  is  1.5526.  Does  not  congeal  at  0°  F.  Analogous  to  perchloride 
of  carbon  in  its  chemical  relations. 

Dichloride  of  Carbon.  Symb.  2C+C1,  or  C2C1.  Eq.  47.66.  Obtained  during  the  dis- 
tillation of  nitric  acid  from  crude  nitre  and  sulphate  of  iron,  in  soft,  adhesive  fibres  of  a 
white  colour  and  peculiar  odour.  Boils  between  350°,  and  460°,  sublimes  at  250.  So- 
luble in  hot  oil  of  turpentine  or  alcohol.  Burns  with  a red  flame. 

Dichloride  of  Sulphur • Symb.  2S-fCl,  or  8201.  Density  1.687.  Discovered 
by  Thomson.*  Prepared  by  passing  chlorine  over  flowers  of  sulphur.  Liquid,  vola- 
tile below  200°,  boils  at  280p.  Emits  acrid  fumes.  Consists  of  35.42  parts  or  l eq. 
chlorine,  and  32.2  parts  or  2 eq.  sulphur.  + 

Perchloride  of  Phosphorus.  Symb.  2P+5C1,  or  P2C15  Equiv.  208.5.  There 
are  two  definite  compounds  of  chlorine  and  phosphorus,  the  nature  of  which  was  first 
satisfactorily  explained  bv  Davy.t  When  phosphorus  is  introduced  into  a jar  of  dry 
chlorine,  it  inflames,  and  on  the  inside  of  the  vessel  a white  matter  collects,  which  is 
perchloride  of  phosphorus.  It  is  very  volatile,  a temperature  much  below  212°  being 
sufficient  to  convert  it  into  vapour.  Under  pressure  it  may  be  fused,  and  it  yields 
transparent  prismatic  crystals  in  cooling. 

Sesquichloride  of  Phosphorus , Symb.  2 P— j-3Cl , or  P2CI3;  Equiv.  137.66,  may 
be  made  by  heating  the  perchloride  with  phosphorus,  or  by  passing  the  vapour  of  phos- 
phorus over  corrosive  sublimate  contained  in  a glass  tube.  It  is  a clear  liquid 
Pike  water,  of  specific  gravity  1.45  ; emits  acid  fumes  when  exposed  to  the  air,  owing 
to  the  decomposition  of  watery  vapour  5 but  when  pure  it  does  not  redden  dry  litmus 
paper.  It  appears  to  consist  of  31.4  parts  or  two  equivalents  of  phosphorus,  and 
106.26  parts  or  3 eq.  of  chlorine. 

Chlorocarbonic  Acid  Gas.  Symb.  CO+Gl,  or  CO, Cl  Equiv.  49.54.  This  com- 
pound was  discovered  in  1812by  Dr  Davy,  who  described  it  in  the  Philos.  Trans,  under 
the  name  of  phosgene  gas.  (From  <p o)g  light,  and  yevvetv  to  produce.)  It  is  made 
by  exposing  a mixture  of  equal  measures  of  dry  chlorine  and  carbonic  oxide  gases  to 
sunshine,  when  rapid  but  silent  combination  ensues,  and  they  contract  to  one  half  their 
volume.  Diffused  daylight  also  effects  their  union  slowly  5 but  they  do  not  combine  at 
all  when  the  mixture  is  wholly  excluded  from  light. 

C hlorocarbonic  acid  gas  is  colourless,  has  a strong  odour,  and  reddens  dry  litmus 
paper.  It  possesses  the  characteristic  property  of  acids.  It  is  decomposed  by  contact 
with  water.  100  cubic  inches  weigh  106.7633  grains.  Its  specific  gravity  is  3.4427, 
and  it  consists  of  35.42  parts  or  one  equivalent  of  chlorine,  and  14.12  parts  or  one 
equivalerit  of  carbonic  oxide. 

Terchlorifie  of  Boron.  Symb.  B+3C1,  or  BC13.  Equiv.  117.16;  eq.  vol.  =•  200. 

Berzelius  found  that  if  boron,  previously  heated,  was  exposed  in  a glass  tube  io  a cur- 
rent of  dry  chlorine,  and  gently  heated  as  soon  as  the  atmospheric  air  was  expelled,  a 
colourless  gas  was  obtained,  which  could  be  collected  over  mercury.  It  may  also  be 
generated  by  the  action  of  dry  chlorine  on  a mixture  of  charcoal  and  boracic  acid  heated 
to  redness  in  a porcelain  tube.  It  is  absorbed  by  water.  Its  sp.  gr.  is  4.0805. 

Terchloride  of  Silicon.  Symb  Si-f-SC l,  or  SiCl3  5 Equiv.  128.76,  is  obtained  by 
heating  silicon  in  a current  of  chlorine  gas.  It  is  a limpid,  volatile  fluid,  boiling  at 
124°  and  not  solid  at  zero.  Its  odour  is  suffocating. 

Oersted  obtained  it  by  mixing  about  equal  parts  of  hydrated  silicic  acid  and  starch 
into  a paste  with  oil,  heating  the  mass  in  a covered  crucible  so  as  to  char  the  starch, 
introducing  the  mixture  in  fragments  into  a porcelain  tube,  and  then  transmitting 
through  it  a current  of  dry  chlorine  while  the  tube  is  kept  at  a red  heat.  The  chlorine 
unites  with  silicon,  and  the  charcoal  and  oxygen  combine.  The  volatile  chloride  is 
then  agitated  with  mercury  to  separate  the  free  chlorine,  and  purified  by  distillation. 

Chloronitrous  Gas.  When  fused  chloride  of  sodium,  potassium,  or  calcium, 
in  powder,  is  treated  with  as  much  strong  nitric  acid  as  is  sufficient  to  wet  it,  mutual 
decomposition  ensues,  and  a new  gas,  composed  of  chlorine  and  binoxide  of  nitrogen, 
is  generated.  It  was  discovered  by  E.  Davy,  who  describes  it  as  of  a pale  reddish 
yellow  colour,  of  an  odour  similar  to  that  of  chlorine,  and  as  having  bleaching  proper- 
ties. 

*For  an  account  of  the  changes  of  opinion  concerning  the  nature  of  chlorine,  see 
Turner,  226. 

In  referring  to  chemical  works  published  before  the  present  views  were  entertained, 

* Nicholson’s  Jour.  vol.  vi.  f Rose — Pog.  dnn.  xxi.  431.  f Elements,  p.  290. 


196 


Iodine. 


Chap.  III. 


Discovery 
of  iodine. 


Occurs  in 
nature. 


Process  for 

obtaining 

iodine, 


Section  XI.  Iodine. 

Symb.  Sp.  Gr.  Chem.  Equiv. 

I.  8. 7020  Air  = l By  Vol.  100 

126.30  Hyd.=  1 “ Wght.  126.3 

671.  Iodine  was  discovered  accidentally  by  Courtois,  a manufac- 
turer of  saltpetre  at  Paris,  in  1812.  In  the  process  for  procuring 
soda  from  the  ashes  of  sea-weeds,  he  found  that  his  metallic  vessels 
were  much  corroded,  and  in  searching  for  the  cause,  he  made  the 
discovery  of  iodine.  Its  real  nature  was  soon  after  determined  by 
Gay-Lussac  and  Davy,  each  of  whom  proved  that  it  is  a simple  non- 
metallic  substance,  exceedingly  analogous  to  chlorine.* 

672.  Iodine  is  frequently  met  with  in  nature  in  combination  with 
potassium  or  sodium.  Under  this  form  it  occurs  in  many  salt  and 
other  mineral  springs,  both  in  Europe  and  America. t It  has 
been  detected  in  the  water  of  the  Mediterranean,  in  the  oyster  and 
some  other  marine  molluscous  animals,  in  sponges,  and  in  most 
kinds  of  sea-weed.  In  some  of  these  productions,  such  as  the  Fucus 
serratus  and  Fucus  digitatus , it  exists  ready  formed,  and  according 
to  Fyfet  may  be  separated  by  the  action  of  water;  but  in  others  it 
can  be  detected  only  after  incineration.  Marine  animals  and  plants 
doubtless  derive  from  the  sea  the  iodine  which  they  contain.  Vau- 
quelin  found  it  also  in  the  mineral  kingdom,  in  combination  with 
silver.^ 

673.  Iodine  is  procured  from  the  impure  carbonate  of  soda,  called 
kelp, II  which  is  prepared  in  large  quantity  on  the  northern  shores  of 
Scotland,  by  incinerating  sea-weeds.  The  kelp  is  employed  by  soap- 
makers,  for  the  preparation  of  carbonate  of  soda ; and  the  dark  resi- 
dual liquor,  remaining  after  that  salt  has  crystallized,  contains  a con- 
siderable quantity  of  iodine,  combined  with  sodium  or  potassium. 
By  adding  a sufficient  quantity  of  sulphuric  acid,  hydriodic  acid  is 
first  generated,  and  then  decomposed. 


the  following  memoranda  will  enable  the 
employed  into  the  present  nomenclature. 

According  to  the  old  doctrine. 

1.  Chlorine  is  a compound  of  muriatic 
acid  23  + Oxygen  8 = 36.* 

2.  Muriatic  acid  gas  consists  of  28  real 
acid  -|-  9 water  = 37. 

3-  Muriatic  acid  gas,  acting  on  oxides, 
gives  out  its  combiued  water,  the  real 
acid  23  combining  with  the  oxide. 


* The  originalpapers on  this  subject  are 
xci  , and  in  the  Philos.  Trans,  for  1814  an 
+ On  iodine  in  the  waters  of  Saratoga,  se 


student  to  translate  the  language  formerly 

According  to  Davy. 

1.  Chlorine  is  an  element. 

2.  Muriatic  acid  gas  is  the  real  acid,  and 
contains  no  water,  consisting  of  chlo- 
rine 36  + hydrogen  1 = 37. 

3.  Muriatic  acid  gas  acting  on  oxides  is 
decomposed,  its  hydrogen  uniting  with 
the  oxygen  of  the  oxide,  and  producing 
the  water  which  is  detached,  while  a 
compound  of  chlorine  and  the  metal  is 
left.  Reid’s  Text  Book. 

n the  Ann.  de  Chim.  vols.  lxxxviii.,  xc.  and 
l 1815. 

: Amer.  Jour.  xvi.  242. 


t Edin.  Philos.  Jour.  t.  254.  § An.  de  Ch.  etde  Ph.  xxix. 

||  For  a method  of  determining  the  proportions  of  iodine  in  kelp,  &c.  see  Jour,  de 
Chem.  Med.  Aug.  1838,  aud  Lond.  and  Edin.  Phil.  Mag.  xiii.  468. 


* The  numbers  giyen  by  Reid  are  retained,  but  can  readily  be  made  to  correspond  with  the 
more  correct  numbers  of  Turner. 


197 


Properties  of  Iodine . 

Lixiviate*  powdered  kelp  with  cold  water.  Eva- 
porate the  lixivium  till  a pellicle  forms,  and  set 
aside  to  crystallize.  Evaporate  the  mother  liquor 
to  dryness,  and  pour  upon  the  mass  half  its  weight 
of  sulphuric  acid.  Apply  a gentle  heat  to  this  mix- 
ture in  the  flask  a of  the  alembic  shown  in  Fig.  165, 
of  which  the  head  or  capital  6,  has  a tube  issuing 
from  it,  and  descending  into  the  receiver  c.  Fumes 
of  a violet  colour  arise  and  condense  in  the  form  of 
opaque  crystals,  having  a metallic  lustre,  which  are 

to  be  washed  out  of  the  head  of  the  alembic  with  a small  quantity  of  water,  and 
quickly  dried  upon  bibulous  paper. 

674.  A more  convenient  process  is  to  employ  a moderate  excess  of  sulphuric  Another, 
acid,  and  then  add  to  the  mixture  some  peroxide  of  manganese,  which  acts  on 
hydriodic  in  the  same  way  as  on  hydrochloric  acid  (608).  Another  method, 
proposed^by  Soubeirain,  is  by  adding  to  the  ley  from  kelp  a solution  made  with 

the  sulphates  of  protoxides  of  copper  and  iron  in  the  ratio  of  1 of  the  former  to 
of  the  latter,  as  long  as  a white  precipitate  appears.  The  diniodide  of  copper  is 
thus  thrown  down ; and  it  may  be  decomposed  either  by  peroxide  of  manganese 
alone,  or  by  manganese  and  sulphuric  acid.  By  means  of  the  former,  the  iodine 
passes  over  quite  dry  ; but  a strong  heat  is  requisite. 

675.  As  the  liquid  directed  to  be  used  (673)  may  not  be  easily  procured,  the  me- 
thod of  preparing  iodine  may  be  shown,  by  mixing  a little  pure  hydriodic  acid  with 
the  peroxide  of  manganese  in  a small  tube  or  glass  retort. 

676.  Iodine  is  a solid  at  the  ordinary  temperature  of  the  atmos-  Properties, 
phere.  It  is  often  in  scales  resembling  those  of  micaceous  iron  ore; 
sometimes  in  large  and  brilliant  rhomboidal  plates,  the  primitive 

form  of  which  is  a rhombic  octohedron.  Its  colour  is  bluish  black  ; 
its  lustre  metallic  ; it  is  soft  and  friable,  and  a non-conductor  of  elec- 
tricity. It  produces  a.  yellow  stain  upon  the  skin.  Its  smell  resem- 
bles that  of  diluted  chlorine.  Its.  taste  is  acrid.  Its  sp.  gr.  according 
to  Gay-Lussac  is  4.948,  but  Thomson  found  it  only  3.0844. 

Iodine  is  fusible  at  225°  F.  and,  under  the  ordinary  pressure 
of  the  atmosphere,  is  volatilized  at  a temperature  somewhere  near 
350°. 

677.  Its  vapour  is  very  dense,  its  sp.  gr.  being,  by  calculation  as  al-  Vapour  of. 
ready  given,  or,  as  directly  observed  by  Dumas,  8.716  ; hence  100 
cubical  inches  weigh  269.8638  grains. 

The  volatilization  of  iodine  at  the  heat  of  boiling  water,  which  hap- 
pens when  it  is  distilled  with  that  fluid,  depends  on  its  affinity  for 
aqueous  vapour. 

The  colour  of  the  vapour  of  iodine  is  a beautiful  violet,  and  hence 
its  name,  (from  violaceus.) 

This  may  be  exhibited  by  introducing  a few  scales  of  iodine  into  a glass  ma-  Exp- 
trass,  and  heating  it  over  a few  coals. 

678.  Like  chlorine  and  oxygen,  iodine  is  a negative  electric.  It  Other  pro- 
renders vegetable  colours  yellow.  It  is  very  sparingly  soluble  in  perlies’ 
water,  that  liquid  not  holding  more  than  TTrbo  its  weight  in  solution  ; 

the  colour  of  the  solution  is  yellow.  It  is  much  more  soluble  in  spirit 
of  wine  and  in  ether.  It  acts  energetically  on  the  animal  system  as 
an  irritant  poison,  but  is  employed  medicinally  in  very  small  doses 
with  advantage. 

679.  Iodine  manifests  a strong  attraction  for  the  pure  metals  and 
for  the  most  of  the  simple  non-metallic  substances.  These  combina- 


* When  water  is  poured  upon  certain  bodies  for  the  purpose  of  extracting  their  saline 
ingredients,  the  process  is  called  lixiviation,  and  the  solution  obtained,  a lixivium. 

For  details  see  Ure’s  Diet.,  article  Iodine. 


198 


Chap. Ill, 
Iodides. 


Action  of 
imponder- 
ables. 


Test  for 
iodine. 


Equivalent. 


Formed. 


Process. 


Iodine  and  Hydrogen. 

ttons  are  termed  Iodides  or  lodurets.  It  is  not  inflammable  ; but 
under  favourable  circumstances  may,  like  chlorine,  be  made  to  unite 
with  oxygen.  A solution  of  the  pure  alkalies  acts  upon  it  giving  rise 
to  the  decomposition  of  water.  Whether  a hypo-iodite  and  iodide 
are  first  produced,  as  in  the  case  of  chlorine,  has  not  yet  been  deter- 
mined, but  on  the  application  of  heat  an  iodate  and  iodide  are 
formed,  t. 

680.  Pure  iodine  is  not  influenced  chemically  by  exposure  to  the 
direct  solar  rays,  or  to  strong  shocks  of  electricity.  It  may  be  passed 
through  red-hot  tubes,  or  over  intensely  ignited  charcoal,  without 
any  appearance  of  decomposition  ; nor  is  it  affected  by  the  agency  of 
galvanism.  Chemists,  indeed,  are  unable  to  resolve  it  into  more 
simple  parts,  and  consequently  it  is  regarded  as  an  elementary  prin? 
ciple. 

681.  The  most  delicate  test  of  the  presence  of  iodine,  is  starch, 
and  if  added  to  any  liquid  containing  it,  with  a few  drops  of  sulphu- 
ric acid,  a blue  compound  is  formed  which  is  insoluble  in  water. 
According  to  Stromeyer,  a liquid  containing  but  jyu.Vxnr  of  its 
weight  of  iodine,  receives  a blue  tinge  from  a solution  of  starch. 
Two  precautions  should  be  observed  to  ensure  success.  In  the  first 
place  the  iodine  must  be  in  a free  state  ; for  it  is  the  iodine  itself 
only,  and  not  its  compounds,  which  unite  with  starch.  Secondly,  the 
solution  should  be  quite  cold  at  the  time  of  adding  the  starch  ; for 
boiling  water  decomposes  the  blue  compound,  and  consequently  re? 
moves  its  colour.* 

6S2.  By  expelling  the  iodine  from  fused  iodide  of  silver  by  a cur- 
rent of  chlorine  gas  and  thus  obtaining  a chloride,  the  composition 
of  which  was  known,  Berzelius  inferred  the  equivalent  of  the  iodide, 
and  from  that  the  equivalent  of  iodine. 

Hydriodic  Acid. 

Composition. 

Foi'm-  Sp.  Gt.  Iod • Hyd.  Equiv. 

H+I,  or  HI  4.3854  Air  = i 126.3  1 eq.  + 1 ==  By  Weht.  127.3 

63.65  Hyd.  = 1 “ Vol.  200 

683.  When  a mixture  of  hydrogen  and  the  vapour  of  iodine  is 
transmitted  through  a red  hot  porcelain  tube,  direct  combination 
takes  place  and  hydriodic  acid  gas  is  formed. 

This  gas  may  be  obtained  by  mixing  one  part  of  phosphorus  with 
ten  of  iodine  moistened  with  water,  placing  it  previously  in  a very 
small  glass  retort  or  flask,  and  applying  a gentle  heat  with  a spirit 
lamp. 

In  a short  time,  a brisk  reaction  commences,  a slight  explosion  generally 
taking  place  within  the  retort  from  the  heat  produced  inflaming  a portion  of 
phosphorus,  and  also  from  the  disengagement  of  a little  phosphuretted  hydro- 
gen. Dense  vapours  are  at  the  same  time  disengaged,  and  the  hydriodic  acid 


*To  render  this  test  more  sure  Balard  recommends  the  following:  After  mixing  the 
liquid  containing  the  iodine  with  the  starch  and  the  sulphuric  acid,  a small  quantity  of 
aqueous  solution  of  chlorine  is  to  be  added  which  from  its  lightness  may  be  made  not 
to  mix  with  the  mixture,  but  float  on  the  surface ; at  the  place,  however,  where  they 
touch,  a blue  zone  will  be  developed  where  the  two  solutions  are  in  contact,  but  if  the 
whole  be  mixed,  it  will  entirely  disappear,  if  the  chlorine  be  in  excess — Ann.  dc  Chim. 
xxxviii.  See  Hayes  in  Amer.  Jour,  xxiii.  142. 


199 


Hydriodic  Acid. 

gas  may  be  collected  by  displacement;  (Fig.  150)  after  these  have  been  expel-  Sect.  XL 

led,  a few  drops  of  water  should  be  introduced  from  time  to  time,  by  a small : — 

pipette,  as  phosphuret  of  iodine  is  sublimed  into  the  neck  of  the  vessel  when 
the  materials  are  dry*  and  no  gas  is  produced.  Phosphuretted  hydrogen  is  dis- 
engaged in  considerable  quantity  towards  the  end  of  the  operation  ; when  it 
begins  to  come  it  is  recognised  by  the  acid  gas  with  which  it  is  mixed,  producing 
a whiter  coloured  vapour  than  usual  with  the  air,  the  process  should  then  be 
stopped,  to  prevent  it  from  accumulating.  Fifty  or  an  hundred  grains  of  iodine, 
with  the  proper  quantity  of  phosphorus,  will  be  found  quite  sufficient,  using  a 
retort  capable  of  containing  about  5 or  6 ounces  of  water.  Constant  attention 
must  be  paid  to  this  operation  while  it  is  going  on.* 

684.  A number  of  complicated  changes  take  place  during  the  Theory, 
reaction  of  the  different  substances  employed,  and  part  of  the  newly 
formed  products.  The  hydriodic  acid  gas  is  produced  by  the  iodine 
combining  with  the  hydrogen  of  a portion  of  water  which  is  decom- 
posed, the  oxygen  uniting  with  the  phosphorus. 

685.  100  measures  of  hydriodic  acid  gas  contain  precisely  half  Equivalent 
their  volume  of  hydrogen.  Assuming  it  to  consist  of  equal  vol- and  deusi" 
umes  of  hydrogen  gas  and  iodine  vapour  united  without  any  conden-ty‘ 
sation,  then,  since 

50  cubic  inches  Of  the  vapour  of  iodine  weigh  . 1 34  :931 9 grains. 

50  do.  hydrogen  gas  ....  1,0683  “ 

100  cubic  inches  of  hydriodic  acid  gas  should  weigh  136.0002 
These  numbers  are  obviously  in  the  ratio  of  1 to  126.3,  the  equi- 
valents of  iodine  and  hydrogen.  On  the  same  principles  the  density 
of  the  gas  should  be  4.3854,  which  is  probably  more  correct  than 
4.443,  a number  found  experimentally  by  Gay-Lussac.t  Hence  100 
measures  of  hydriodic  acid  gas  contain  50  measures  of  hydrogen  gas 
and  50  of  the  vapour  of  iodine. 

When  hydriodic  acid  gas  is  conducted  into  water  till  that  liquid  is 
fully  charged  with  it,  a colourless  acid  solution  is  obtained,  which 
emits  white  fumes  on  exposure  to  the  air,  and  has  a density  of 

1.7.  T 

686.  Hydriodic  acid  gas  has  a sour  taste,  reddens  vegetable  blue  Properties, 
colours,  produces  dense  white  fumes  with  atmospheric  air,  and  re- 
sembles hydrochloric  acid  in  its  odour.  It  combines  with  alkalies  and 

forms  salts  called  hydriodates.  It  is  rapidly  absorbed  by  water. 

Remove  a tube  filled  with  the  gas*  having  closed  the  open  end  with  the  fin-  Exp. 
ger,  into  a basin  of  water  and  remove  the  finger  under  the  water. 

687.  The  gas  is  decomposed  by  several  substances  which  have  a Decompo- 
strong  affinity  for  either  of  its  elements.  Thus  oxygen  gas,  when  sed? 
heated  with  it  unites  with  its  hydrogen,  and  liberates  the  iodine. 

Chlorine  effects  the  decomposition  instantly. 

Fill  a small  jar  half  full  of  hydriodic  acid  gas  over  the  mercurial  trough,  invert 
it  with  a tray,  keeping  the  mouth  of  the  jar  upwards,  and  bring  cautiously  in  con- 
tact  with  it  the  extremity  of  a narrow  tube,  or  the  beak  of  a small  retort,  from 
which  chlorine  is  slowly  escaping ; 50  or  60  grs.  of  peroxide  of  manganese  may 
be  employed  with  a proper  proportion  of  hydrochloric  acid,  and  a retort  capable 
of  holding  1 or  2 o£.  measures.  The  chlorine  combines  with  the  hydrogen  of  the 
hydrochloric  acid,  and  purple  vapours  of  iodine  appear  which  will  condense.  If 
much  chlorine  be  brought  at  once  in  contact  with  the  acid  gas,  an  explosion  takes 
place. i 


* Reid,  Elem.  208.  t An.  de  Ck.  xci.  16. 

t The  chlorine  should  be  allowed  to  come  for  some  time  before  it  is  applied  to  the 


200 


Iodine  and  Hydrogen. 


Chap.  III.  Place  a small  jar  filled  with  the  gas  over  mercury,  the  iodine  will  combine  with 
that  metal  and  the  hydrogen  be  left. 

by  mercury,  invert  a jar  full  of  the  gas  with  an  earthen  dish,  and  pour  into  it  some  strong 
fuming  nitric  and  nitrous  acids.  The  hydrogen  of  the  hydriodic  acid  will  com- 
an.d  nilrous  bine  with  the  oxygen  of  the  nitrous  acid  and  iodine  be  set  free.  The  mixture  of- 
acid.  ten  inflaraes  even  when  no  more  than  two  or  three  cubic  inches  of  the  gas  are 
used. 


Its  solution 
used  as  a 
test, 

Decompo- 

sed. 


Test. 


688.  A solution  of  this  gas  in  water  is  much  employed  as  a test, 
and  may  be  made  by  decomposing  the  iodide  of  starch  suspended  in 
water,  by  a stream  of  hydrosulphuric  acid.* * 

689.  The  solution  of  hydriodic  acid  is  decomposed  by  mere  expo- 
sure to  the  air,  oxygen  unites  to  its  hydrogen,  and  the  iodine  is  set 
free.  Nitric  and  sulphuric  acids  also  decompose  it ; and  chlorine 
unites  to  its  hydrogen  to  form  hydrochloric  acid. 

690.  Bichloride  of  platinum  is  a most  delicate  test  of  hydriodic 
acid.  Pour  a few  drops  into  a glass  containing  an  ounce  or  two  of 
water,  add  a single  drop  of  a solution  of  the  bichloride  of  platinum, 
the  liquid  will  become  of  a reddish  brown  colour,  and  a dark  precipi- 
tate subside. 

Its  effect  upon  metallic  solutions  may  be  seen  as  follows : Added 
to  solution  of  nitrate  of  silver,  it  affords  a yellow  precipitate ; with 
bichloride  of  mercury,  a yellow  and  finally  a red  precipitate ; with 
acetate  of  lead,  a yellow. 


Oxide  of  Iodine  and  Iodous  Acid. 

691.  When  the  vapour  of  iodine  and  oxygen  gas  are  heated,  a 
yellow  matter  of  the  consistence  of  solid  oil  is  generated,  whicli  has 
been  regarded  as  an  oxide  of  iodine.  If  the  supply  of  oxygen  is  conti- 
lodous  nued,  it  is  converted  into  a yellow  liquid  supposed  to  be  iodous  acid.t 
acid. 


Iodic  Acid. 

Composition. 

Form.  lod.  Oxy.  Equvo. 

1+50,  I,  or  10s  126.3  1 cq.  +-  40  5 eq.  = 166.3 

Iodic  acid  692.  This  acid  was  discovered  by  Gay-Lussac  and  Davy.  It  is 
obtained  by  bringing  iodine  into  contact  with  the  euchlorine  of 
Davy  ; the  chlorine  unites  with  one  portion  of  iodine,  and  the  oxygen 


hydriodic  acid  gas,  that  all  the  air  may  he  expelled.  Three  or  four  cubic  inches  of 
this  gas  are  quite  sufficient  for  this  experiment;  the  operator  should  place  the  **cssel 
from  which  the  chlorine  escapes  on  a retort  stand  and  in  such  a situation  that  any  ex- 
cess of  gas  may  be  carried  away  by  a current  of  air. 

* Jour.  Sci.  N.  S.  No.  viii. 

Sixty  grains  of  iodine  are  dissolved  in  3 ounces  of  alcohol  (kept  cold),  and  an  ounce 
of  starch  reduced  to  a very  fine  powder  diffused  in  4 ounces  of  wa- 
ter; on  adding  this,  drop  by  drop,  to  the  first  solution,  and  stirring 
it  constantly  at  the  same  time,  iodide  of  starch  is  formed  ; theclear 
liquid  is  decanted  after  the  iodide  has  subsided.  A little  water  is 
then  poured  on  it  to  remove  any  alcohol  that  may  be  still  mixed  with 
it,  and  after  this  has  been  removed,  the  iodide  is  diffused  through  an 
ounce  of  water,  and  a stream  of  hydrosulphuric  acid  gas  from  400  or 
500  grs.  of  the  sulphuret  of  iron  passed  through  it  till  it  becomes 
white.  Filter  the  liquid  and  boil  for  a short  time  to  expel  any  ex- 
cess of  hydrosulphuric  acid.  The  iodide  of  starch  may  be  put  into 
a precipitate  glass,  when  it  is  diffused  through  water,  and  the  hy- 
drosulphuric acid  prepared  in  a bottle  with  a bent  tube  fitted  to  it.  (Fig.  166.) 

t Quart.  Jour,  of  Sci.  N.  S.  I 


Fie.  166. 


201 


Teriodidt  of  Nitrogen. 

with  another,  forming  two  compounds,  a volatile  orange  coloured 
matter,  chloride  of  iodine,  and  a white  solid  substance  which  is  iodic 
acid.  On  applying  heat,  the  former  passes  off  in  vapour,  and  the 
latter  remains.^ 

Another  process  is  by  boiling  iodine  in  pure  nitric  acid  of  density  1 .5  ; the  acid, 
with  about  one  fifth  of  its  weight  of  iodine,  is  placed  in  a tube  sealed  at  one  end, 
about  an  inch  wide  and  fifteen  inches  long.  The  boiling  should  be  continued  at 
least  twelve  hours.  As  the  iodine  rises  and  condenses  on  the  sides  of  the  tube,  it 
should  be  restored  to  the  liquid,  either  by  agitation  or  by  help  of  a glass  rod.  As 
soon  as  the  iodine  disappears,  the  nitric  acid  is  dissipated  by  cautious  evapora- 
tion, t 

It  is  also  obtained  by  the  oxidizing  effect  of  hypochlorous  acid  on 
iodine,  and  by  several  other  processes. I 

693.  It  is  a white,  semitransparent  solid,  having  a very  acid  as- 
tringent taste.  It  acts  powerfully  on  inflammable  substances,  and 
enters  into  combination  with  metallic  oxides,  forming  iodates.  These 
compounds,  like  the  chlorates,  yield  pure  oxygen  by  heat. 

694.  It  forms  salts  with  the  alkalies  which  are  soluble  in  water. 

It  is  readily  detected,  being  deoxidized  by  sulphurous,  phospho- 
rous, hydriodic  and  hydrosulphuric  acids,  iodine  being  set  at  liberty, 
which  may  be  detected  by  starch. 

695.  When  decomposed  by  heat  it  is  resolved  into  oxygen  gas 
and  pure  iodine;  and  it  was  therefore  termed  by  Davy  oxyiodine, 
and  by  Gay-Lussac  acide  iodique  anhydre .'§ 

Teriodide  of  Nitrogen. 

Composition. 

Form.  Iodine.  Nit.  Equiv. 

N-f3l,  or  NI3  378.9  3 eq.  + 14.15  1 eq.  = 393.05 

696.  From  the  weak  affinity  that  exists  between  iodine  and  nitro- 
gen, these  substances  cannot  be  made  to  unite  directly.  But  when 
iodine  is  put  into  a solution  of  ammonia,  the  alkali  is  decomposed ; 
its  elements  unite  with  different  portions  of  iodine,  and  thus  cause 
the  formation  of  hydriodic  acid  and  iodide  of  nitrogen. 

It  may  be  procured  by  pouring  a solution  of  ammonia  upon  a very 
small  quantity  of  iodine.  Hydriodic  acid  is  one  product,  and  the 
other  a brown  powder,  which  detonates  upon  the  slightest  touch,  and 
is  resolved  into  nitrogen  and  iodine.  It  maybe  collected  by  pouring 
off  the  liquid,  and  placing  it,  while  moist,  in  small  parcels  upon  bibu- 
lous paper,  where  it  must  be  suffered  to  dry  spontaneously. 

If  we  collect  the  powder  on  two  or  more  separate  pieces  of  paper,  and  place 
them  at  several  inches  apart,  the  explosion  of  any  one  of  them  will,  sometimes, 
cause  that  of  the  others. 

* Phil.  Trans.  1815.  t Connell  in  Edin.  Phil.  Jour.  1831,  72,  and  1832,  337. 

t For  which  see  Turner,  232. 

§ Periodic  Acid , Form.  1+70,  I or  IO7,  is  analogous  in  composition  to  per- 
chloric acid,  and  has  decided  acid  properties.  For  process  see  Turner  232. 

Chlorides  of  Iodine.  Chlorine  is  absorbed  at  common  temperatures  by  dry 
iodine  with  evolution  of  heat,  and  a solid  compound  of  iodine  and  chlorine  results, 
which  was  discovered  both  by  Davy  and  Gay-Lussac.  The  colour  of  the  product  is 
orange-yellow  when  the  iodine  is  fully  saturated  with  chlorine,  but  is  of  a reddish- 
orange  if  iodine  is  in  excess.  Its  solution  is  colourless,  very  sour  to  the  taste,  and 
reddens  vegetable  blue  colours,  but  afterwards  destroys  them.  From  its  acid 
properties  Davy  gave  it  the  name  of  chloriodic  acid.  Souberain  has  lately  distin- 
guished a compound  of  3 eq.  of  chlorine  and  1 of  iodine.* 

* Jou,r.  de  Phar.  Feb.  1837. 


Sect.  XI. 


Process. 


Properties. 


Decompo- 

sition. 


Process. 


Exp. 


Chloride  of  io. 
dine. 


26 


202 


Bromine. 


ch»p«  m»  When  left  exposed  it  gradually  evaporates.  It  often  explodes 
spontaneously.  When  it  detonates,  the  purple  fumes  of  iodine  are 
perceptible. 

697.  Iodides  of  phosphorus . Iodine  and  phosphorus  combine  on 
being  brought  in  contact,  and  so  much  heat  is  evolved  that  part  of 
the  phosphorus  is  inflamed  if  the  air  be  not  excluded. 

EXp.  A small  piece  of  phosphorus  may  be  placed  in  a wine  glass  and  iodine  let  fall 

upon  it  from  a card  or  broad  knife,  combustion  ensues  and  iodine  vapour  escapes. 

Iodine  and  phosphorus  can  combine  in  various  proportions.^ 


Discovery. 


Process  for 

obtaining 

bromiae. 


Section  XII.  Bromine. 

* Symb.  Sp.  Gr.  Chem.  Equiv. 

Br  5.4017  Air  = 1 By  Vol.  100 

78.40  Hyd.  = 1 “ Wght.  78.4 

698.  In  1S26  Balardt  of  Montpellier  discovered  in  sea  water  a 
new  substance  to  which  he  gave  the  name  muride  ; but  it  has  since 
been  changed  to  Bromine , a word  derived  from  the  Greek  fiswfios 
( graveolentia ) signifying  a strong  or  rank  odour. 

699.  Bromine  exists  in  sea  water  in  the  form  of  bromide  of 
sodium  or  magnesium.  It  may  apparently  be  regarded  as  an  essen- 
tial ingredient  of  the  saline  matter  of  the  ocean.  It  has  also  been 
found  in  the  waters  of  the  Dead  Sea,  and  in  a variety  of  salt  springs. 
It  is  present,  however,  in  very  small  quantity  ;t  and  even  the  un- 
crystallizable  residue  called  bittern,  left  after  the  salt  has  been  sepa- 
rated from  sea  water  by  evaporation,  contains  but  little  of  it.§ 
Daubeny  has  detected  it  in  several  mineral  waters,  and  Balard  in 
marine  plants  on-  the  shores  of  the  Mediterranean,  in  the  ashes  of 
sea  weeds,  and  of  some  animals,  as  the  Idnthina  violacea. 

700.  It  is  obtained  by  passing  a stream  of  chlorine  through  the 
bittern,  and  exposing  it  afterwards  to  heat ; the  bromine  distils  over 
and  may  be  collected  in  a receiver.  A few  ounces  of  concentrated 
bittern  are  sufficient  to  show  this  process.  In  preparing  the  liquid. 


Periodid* * * §  of 
carbon. 


* Iodide  of  Sulphur  is  prepared  with  4 parts  of  iodiue  and  1 of  sulphur  healed 
gemly- 

Periodide  of  Carbon  is  formed  when  a solution  of  pure  potassa  in  alcohol  is 
mixed  with  an  alcoholic  solution  of  iodine,  a portion  of  the  alcohol  is  decomposed  ; its 
hydrogen  and  carbon  uniting  separately  with  iodine,  give  rise  to  periodide  of  carbon, 
and  hydriodic  acid.  By  distilling  a mixture  of  the  preceding  with  corrosive  sublimate, 
the  protiodide  is  formed. 

+ The  original  essay  of  Balard  was  published  in  the  Ann.  de  Chim.  et  de  Phys. 
Aug.  1826,  and  an  abstract  of  it  in  the  Edin.  Jour,  of  Sci. 

t One  hundred  pounds  of  sea  water  yield  but  3.278  grains  of  bromine.  Quart . 
Jour.  1827. 

§ I have  obtained  it  from  the  bittern  of  the  salt  works  in  the  vicinity  of  Boston  (W.), 
and  Hayes  has  found  it  in  the  waters  of  Saratoga.  Amer.  Jour,  xviii.  142. 

Hare*'  method  Hayes  recommends  the  following  as  a method  of  detecting  the  presence  of  extremely 
of  detecting  minute  quantities  of  bromine  and  iodine.  Mix  a few  drops  of  pure  water  in  a conical 

bromin*.  glass,  with  a drop  of  sulphuric  acid,  and  half  a volume  of  a cold  solution  of  starch  : 

pass  a few  bubbles  of  chlorine  through  the  mixture,  which  is  then  left  at  rest,  that  the 
diffused  starch  may  unite  at  bottom.  A glass  rod,  dipped  in  the  fluid  supposed  to 
contain  bromine,  is  then  applied  to  the  surface  of  the  fluid  in  the  glass;  orange- 
coloured,  dense  striae  descend  from  the  rod,  and  rest  for  some  time  on  the  starch  if 
bromine  alone  is  present.  If  the  solution  contains  iodine  also,  the  appearance  is  the 
same,  but  the  striae  are  deep  blue ; in  a few  seconds  the  blue  disappears,  and  the  cha- 
racteristic orange  yellow  of  the  solution  of  bromine  remaius.  Amer.  Jour,  xviii.  142. 


203 


Hydrobromic  Acid'. 

the  chlorine  must  be  transmitted  through  it  till  the  orange  colour  Sect,  xn. 
which  it  acquires  ceases  to  become  deeper.  The  chlorine  which  is 
procured  from  290  or  300  grains  of  peroxide  of  manganese  will  be 
quite  sufficient  for  passing  through  five  or  six  ounces  of  bittern. 

701.  Bittern  consists  principally  of  sulphates  and  hydrochlorates  Theory, 
of  soda  and  magnesia,  with  a small  quantity  of  the  hydrobromate  of 
magnesia,  the  hydrobromic  acid  of  which  is  composed  of  hydrogen 

and  bromine.  The  chlorine  combines  with  the  hydrogen  and  disen- 
gages the  bromine,  which  imparts  a yellow  colour  to  the  liquid.  The 
vapour  of  the  bromine  has  a deep  reddish  brown  colour  and  con- 
denses into  a very  dark  coloured  liquid. 

There  are  other  processes.  A current  of  chlorine  may  be  trans-  Other 
mitted  through  the  bittern,  and  it  may  then  be  shaken  with  sulphuric  Processes* 
ether,  which  will  dissolve  the  bromine,  and  acquire  a hyacinth  red 
tint.  When  the  ethereal  solution  is  agitated  with  caustic  potassa, 
its  colour  entirely  disappears,  owing  to  the  formation  of  bromide  of 
potassium  and  bromate  of  potassa,  the  former  of  which  is  obtained  in 
cubic  crystals  by  evaporation.  The  bromine  maybe  set  free  by 
means  of  chlorine,  or  still  better  by  sulphuric  acid  and  peroxide  of 
manganese  in  a glass  retort  dipping  into  cold  water. 

702.  Bromine  is  liquid  at  common  temperatures  with  a deep  hya-  Properties, 
cinthine  red  colour.  It  volatilizes  readily  and  its  vapour  is  highly 
coloured,  having  a density  of  5.54,*  100  cubic  iuches  at  60°  should 

weigh  167.5158  grs.  Its  sp.  gr.  is  about  3.  At  116.5°  it  boils,  and  Specific 
is  frozen  and  brittle  at  — 4°.  It  communicates  a yellow  stain  to  the  §ravity- 
skin  and  acts  powerfully  upon  organic  bodies.  It  is  highly  fatal 
to  animal  life ; a bird  is  killed  by  a single  drop  placed  on  its  beak. 

Bromine  has  not  been  decomposed  ; it  is  an  imperfect  conductor  of 
electricity,  and  a negative  electric.  It  is  soluble  in  water,  alcohol  and 
ether,  and  has  the  property  of  bleaching. 

703.  The  vapour  of  bromine  extinguishes  a lighted  taper,  which, 

at  first,  burns  with  a flame  green  at  its  base,  and  red  at  its  upper  Action  on 
part.  Some  inflammables  take  fire  by  contact  with  it.  Thus  combusti- 
antimony  and  tin  burn  in  it,  and  the  combustion  of  potassi- b es’ 
um  is  attended  with  intense  heat  and  a vivid  flash,  and  the  vessel  in  Apdmet- 
which  the  experiment  is  made  is  often  broken.  Its  affinity  for  metal- 
lic oxides  is  feeble. 

704.  Bromine  is  analogous  to  chlorine  and  iodine  in  its  chemical  Analogous 
relations,  and  suffers  the  same  kind  of  change  as  those  bodies  simi-  jo  chlorine 
larly  treated.  Its  presence  is  in  general  easily  detected  by  chlorine  &c' 

and  the  colour  of  its  vapour,  or  of  its  solution  in  ether. 

Hydrobromic  Acid • 

Composition. 

Form.  Sp.  Gr.  Broun.  Hijd.  Equiv.  Eq.Vol. 

H+Br.,  or  HEr.  2.7353  Air  = 1 78.4  + 1 = 79,4  200 

39.70  Hyd.  = 1 

705.  This  acid  is  formed  when  a lighted  candle  or  piece  of  red-hot  When 
iron  is  introduced  into  a mixture  of  the  vapour  of  bromine  and  hy-  formed, 
drogen  gas ; and  by  the  action  of  bromine  on  some  of  the  gaseous 
compounds  of  hydrogen. 


* Mitscherlicb. 


204 


Chap.  HI. 
Process. 


Properties. 


Solution. 


Action  of 
chlorine. 


Weight 
and  equiva- 
lent. 


Bromic 

acid. 


Process  for, 


Properties 

of. 


Bromine  and  Oxygen. 

It  may  be  conveniently  made  for  experimental  purposes  by  a process  similar  to 
that  for  forming  hydriodic  acid.  A mixture  of  bromine  and  phosphorus  slightly 
moistened,  yields,  by  the  aid  of  gentle  heat,  a large  quantity  of  pure  hydrobromic 
acid  gas,  which  should  be  collected  either  in  dry  glass  bottles,  or  over  mercury. 

706.  It  is  a pungent,  colourless,  acid  gas,  undergoing  no  decompo- 
sition when  transmitted  through  a red-hot  tube,  either  alone  or  mixed 
with  oxygen,  but  is  decomposed  instantly  by  chlorine.  It  may  be 
preserved  without  change  over  mercury ; but  potassium  and  tin  de- 
compose it  with  facility. 

707.  It  is  very  soluble  in  water,  and  the  solution  may  be  made  by 
treating  bromine  with  hydrosulphuric  acid  dissolved  in  water,  or  still 
better  by  transmitting  a current  of  hydrobromic  acid  gas  into  pure 
water.  The  liquid  becomes  hot  during  the  condensation.  This  acid 
solution  is  colourless  when  pure,  but  possesses  the  property  of  dis- 
solving a large  quantity  of  bromine,  and  then  receives  the  tint  of  that 
substance. 

Chlorine  decomposes  the  solution  of  hydrobromic  acid.  Nitric  acid 
acts  upon  it  less  suddenly,  disengaging  bromine.  Nitro-hydrobromic 
acid  is  analogous  to  aqua  regia , and  possesses  the  property  of  dis- 
solving gold. 

708.  Hydrobromic  is  analogous  to  hydriodic  and  hydrochloric  acid 
gases,  in  containing  equal  measures  of  bromine  vapour  and  hydro- 
gen gas  united  without  any  change  of  volume  ; and  since 

Grs. 

50  cubic  inches  of  bromine  vapour  weigh  . . . 63.7579 

50  do.  hydrogen  gas  ....  1.0683 

100  do.  hydrobromic  acid  must  weigh  . . 84.8262 

These  numbers  are  in  the  ratio  of  1 to  78.4,  which  is  the  composi- 
tion of  the  gas  by  weight.  T.  The  salts  of  hydrobromic  acid  are 
termed  hydrobromates. 

Bromic  Acid. 

Composition. 

Symb.  Brom.  Oxy.  Equiv. 

Br+60,  Br,  or  BrO5.  78.4  1 eq.  + 40  5 eq.  = 118.4 

709.  Bromic  Acid  is  formed  by  the  action  of  bromine  on  potassa, 
when  a change  exactly  similar  to  that  produced  by  chlorine  (page  656) 
ensues,  whereby  bromide  of  potassium  and  bromate  of  potassa  are 
generated  ; and  the  latter,  being  much  less  soluble  than  the  former, 
is  readily  separated  by  evaporation.  The  bromate  of  the  other  alka- 
lies and  alkaline  earths  may  be  prepared  in  a similar  manner. 

710.  Bromic  acid  may  be  procured  by  decomposing  a dilute  solu- 
tion of  bromate  of  baryta  with  sulphuric  acid,  so  as  to  precipitate  the 
whole  of  the  baryta.  The  solution  of  bromic  acid  may  be  concentrated 
by  slow  evaporation  until  it  acquires  the  consistence  of  syrup. 

Bromic  acid  has  scarcely  any  odour,  but  its  taste  is  very  acid, 
though  not  at  all  corrosive.  It  reddens  litmus  paper  powerfully  at 
first,  and  soon  after  destroys  its  colour.  It  is  similar  in  constitution 
to  iodic,  chloric  and  nitric  acids.* 


* Chloride  of  Bromine. — This  compound  may  be  formed  at  common  tempera- 
tures by  transmitting  a current  of  chlorine  through  bromine,  and  condensing  the  disen- 


Hydrofluoric  Acid, 


205 


Section  XIII.  Fluorine.  ~ 

Symb.  F.  Equiv . 18.68  Eq.  Vol.  100 

711.  The  mineral  known  as  Derbyshire  spar  from  the  place  where  Fluorine 
it  occurs  in  great  abundance,  was  considered  to  be  a compound  of  a 
peculiar  acid  and  lime,  and  the  former  was  called  fluoric  acid.  It  was 
suggested  by  Ampere  that  this  mineral  is  a compound  of  fluorine 

and  calcium,  and  this  was  supported  experimentally  by  Davy.  The 
supposed  base  of  the  acid  was  named  fluorine,  but  was  not  obtained 
in  an  insulated  form  until  recently,  and  its  properties  are  but  imper- 
fectly known. 

712.  Fluorine  was  first  procured  by  Baudrimont  by  passing  fluo-  How  ob- 
ride  of  boron  over  minium  (red  oxide  of  lead),  heated  to  redness,  tained. 
and  receiving  the  gas  in  a dry  vessel.  As  it  is  mixed  with  much 
oxygen,  his  present  method  is,  to  treat  a mixture  of  fluoride  of  cal- 
cium and  peroxide  of  manganese  with  strong  sulphuric  acid.  This 
process,  however,  does  not  afford  it  pure,  hydrofluoric  and  fluosilicic 

acid  gases  being  at  the  same  time  evolved.  The  presence  of  the 
latter  does  not  prevent  the  observation  of  some  of  the  properties  of 
fluorine. 

713.  It  appears  to  be  a gaseous  body,  resembling  chlorine  and  Properties, 
burnt  sugar  in  odour,  and  possessed  of  bleaching  properties.  It  does 

not  act  on  glass.  It  is  a negative  electric,  and  has  a powerful  affi- 
nity for  hydrogen  and  metallic  substances. 

Hydrofluoric  Acid. 

Composition. 

Form.  Sp.  Gr.  Flu.  Hyd.  Equiv. 

H-f~F,  or  HP.  1.0609  18.68  1 eq.  -f  1 1 eq.  = 19.68 

714.  Hydrofluoric  acid  was  first  obtained  pure  by  Gay-Lussac  Hydrofluo 

and  Thenard  in  1810.  ric  acid, 

715.  It  is  prepared  by  acting  on  fluor  spar  ( fluoride  of  calcium ),  Process  for. 
by  sulphuric  acid. 

The  spar,  carefully  separated  from  siliceous  earth  and  reduced  to  fine  powder, 
is  put  into  a leaden  or  silver  retort  with  twice  its  weight  of  sulphuric  acid ; 
the  materials  are  mixed  together  with  an  iron  rod,  and  on  applying  a moderate 
heat  by  a chauffer,  the  hydrofluoric  acid  is  disengaged  : a receiver  of  the  same 
metal  must  be  used  to  condense  it.  An  arrangement  like  that  on  the  following 
page  will  be  found  convenient.* 


gaged  vapours  by  means  of  a freezing  mixture.  The  resulting  chloride  is  a volatile 
fluid  of  a reddish  yellow  colour. 

Bromide  of  Iodine. — These  substances  act  readily  on  each  other,  and  appear  capa-  Bromide  of 
ble  of  uniting  in  two  proportions.  iodine,  &c. 

Bromide  of  Sulphur. — On  pouring  bromine  on  sublimed  sulphur,  combination  en- 
sues, and  a fluid  of  an  oily  appearance  and  reddish  tint  is  generated.  Bromide  of 
sulphur  is  decomposed  by  chlorine,  which  unites  with  sulphur  and  displaces  bromine. 

Bromides  of  Phosphorus.*-  When  bromine  and  phosphorus  are  brought  into  contact 
in  a flask  filled  with  carbonic  acid  gas,  they  act  suddenly  on  each  other  with  evolution 
of  heat  and  light,  and  two  compounds  are  generated.  The  protobromide  retains  its 
liquid  form  even  at  52°  F. 

Bromide  of  Carbon  is  formed  by  the  action  of  bromine  on  half  its  weight  of  per- 
iodide  of  carbon,  when  bromide  of  carbon  and  a subbromide  of  iodine  are  formed,  the 
latter  of  which  is  removed  by  a solution  of  caustic  potassa.  At  common  temperatures  it 
is  liquid,  but  crystallizes  at  32°  F.  Its  taste  is  sweet,  and  it  has  a penetrating  ethe- 
real odour. 


* It  is  composed  of  a deep  leaden  cup,  (Fig.  167,)  with  a rim  of  lead  soldered  round  Apparatui  for 
the  top,  a small  space  being  left  between  it  and  the  upper  part  of  the  cup  for  fixing  hydrof.  ac;d.° 


206 


Fluorine  and  Hydrogen . 

Chap.  Hi.  716.  As  the  materials  swell  up  considerably  during  the  process, 

Theory.  the  retort  should  be  capacious.  At  the  close  of  the  operation,  pure 
hydrofluoric  acid  is  found  in  the  receiver,  and  the  retort  contains  dry 
sulphate  of  lime.  The  chemical  changes  are  the  same  as  in  the 
formation  of  hydrochloric  acid  gas  (629),  fluorine  being  substituted 
for  chlorine,  and  calcium  for  sodium.  If  the  sulphuric  acid  is  of 
sufficient  strength,  all  its  water  is  decomposed,  and  the  resulting 
hydrofluoric  acid  is  anhydrous. 

Properties.  717.  This  acid  at  32°  is  a colourless  liquid,  and  remains  such  at 
59°  if  preserved  in  well  stopped  bottles,*  but  when  exposed  to  the 
air,  it  flies  off  in  dense  white  fumes.  It  has  a very  pungent  smell, 
and  is  extremely  destructive  ; if  applied  to  the  skin  it  instantly  kills 
the  part,  producing  extreme  pain  and  extensive  ulceration.  The 
operator  should  carefully  avoid  the  fumes,  and  the  apparatus  or  ves- 
sels containing  the  acid,  should  be  so  placed  that  they  may  be  car- 
ried from  him. 

Action  on  It  acts  powerfully  on  glass,  destroying  its  transparency,  in  conse- 

£lass-  quence  of  attacking  its  silica  and  forming  with  it  a compound  known 
as  fluosilicic  acid  gas , henGe  it  cannot  be  kept  in  glass  vessels  unless 
protected  by  wax. 

Uses.  718.  From  its  affinity  for  silica,  it  is  employed  for  etching  on 

glass,  and  for  this  purpose  should  be  diluted  with  three  or  four  parts 
of  water.  The  glass  should  be  covered  with  a varnish,  prepared  by 
melting  together  bees-wax  and  turpentine,  and  surrounded  at  the 
edge  by  a rim  of  the  same.  The  varnish  is  then  to  be  removed 
- wherever  it  is  desired  to  have  the  acid  act  upon  the  glass,  as  in  the 
process  for  etching  on  copper. 

Exp.  On  a small  scale  the  experiment  may  be  made  by  placing  a small  quantity  of 

the  powdered  fluor  spar  irt  a platinum,  silver,  or  leaden  cup  or  crucible,  support- 
ed over  a lamp  ; covering  the  vessel  with  a piece  of  glass,  coated  by  rubbing  over 
it,  previously  warmed,  a piece  of  wax,  lines  being  traced  through  the  coating  so 
as  to  expose  the  glass.  Or  the  cup  may  be  held  over  the  firef  till  the  vapour  be- 
gins to  escape,  the  glass  is  then  applied  and  the  whole  covered  with  a wooden  or 
pasteboard  box.* 

Acid  pro-  719.  Hydrofluoric  acid  has  all  the  characters  of  a powerful  acid. 

erties. 


in  the  head  of  the  apparatus  when  the  materials 
have  been  put  in.  The  easiest  method  of  proceed- 
ing is  to  fill  this  intervening  space  with  moist 
plaster-of-paris,  and  put  in  the  cover  when  it  be- 
gins to  set,  taking  care  to  have  the  tube  and  the 
bottle  receiver,  which  are  used  along  with  it, 
properly  adjusted  at  the  same  time,  that  it  may 
not  be  necessary  to  shift  it  afterwards.  The  re- 
ceiver is  placed  in  a jar  or  basin,  and  surrounded 
by  ice.  The  heat  should  be  cautiously  applied  j 
so  as  not  to  melt  the  leaden  cup ; the  student 
should  examine  it  occasionally  with  an  iron  rod, 
and  withdraw  the  chauffer  it  it  begins  to  soften 
or  yield  more  than  usual  to  the  iron.  The  body 
of  the  retort  may  be  rather  more  than  two  inches 
in  diameter,  and  between  seven  and  eight  inches 
long  5 it  is  supported  by  an  iron  ring  resting  on  three  rods  of  iron,  and  bound  together 
at  bottom  by  a plate  of  sheet  iron,  on  which  the  chauffer  is  placed.  Two  to  four 
ounces  of  fluor  spar  may  be  used  in  it  at  a time,  or  even  more  if  required.  A more  ex- 
pensive apparatus  is  described  in  Amer.  Jour.  vol.  vi.  355. 

* Which  should  be  lined  with  wax.  t With  tongs,  not  by  the  hand. 

t A little  sand  poured  round  the  box  where  it  rests  on  a table  will  prevent  the  va- 
pours from  annoying  the  operator. 


Fig.  167. 


Fluoboric  Acid. 


207 


It  has  a strong,  sour  taste,  reddens  litmus  paper,  and  neutralizes  al-  Sect. xiii. 
kalies,  either  forming  salts  termed  hydrofiuates , or  most  generally 
giving  rise  to  metallic  fluorides.  All  these  compounds  are  decom- 
posed by  strong  sulphuric  acid  with  the  aid  of  heat,  and  the  hydro- 
fluoric acid  while  escaping  may  be  detected  by  its  action  on  glass. 

720.  Hydrofluoric  acid  acts  violently  on  some  of  the  metals,  espe- 
cially  on  the  bases  of  the  alkalies.  It  is  a solvent  for  some  elemen- 
tary principles  which  resist  the  action  even  of  nitro-hydrochloric  acid, 
with  evolution  of  hydrogen  gas  ; and  when  mixed  with  nitric  acid,  it 
proves  a solvent  for  silicon  which  has  been  condensed  by  heat,  and 
for  titanium.  Nitro-hydrofluoric  acid,  however,  is  incapable  of  dis- 
solving gold  and  platinum. 

Fluoboric  Acid. 

Composition. 

Form.  Flu.  Bor.  Equiv. 

B+3F,  or  BF*.  56.04  3 eq.  -f  10.9  1 eq.  = 66.94 

721.  This  gas  was  procured  by  Gay-Lussac  and  Thenard  from  a 
mixture  of  vitrified  boracic  acid  and  fluor  spar,  exposed  to  heat  in  a 
leaden  retort.  It  was  procured  by  Dr  Davy  by  mixing  intimately  one  Process, 
part  of  fused  boracic  acid  with  twice  its  weight  of  fluor  spar,  both  in 

fine  powder,  and  twelve  parts  of  sulphuric  acid  in  a glass  flask,* 
heating  the  mixture  by  a lamp.  Half  an  ounce  or  an  ounce  and  a 
half  of  the  fused  boracic  acid,  with  the  corresponding  quantity  of 
spar  and  acid  affords  a considerable  quantity  of  the  compound. 

Strong’  sulphuric  acid  should  be  employed.  The  gas  thus  ob- 
tained contains  a considerable  quantity  of  fluosilicic  acid. 

722.  In  the  decomposition  of  fluor  spar  by  vitrified  boracic  acid,  Theory, 
the  former  and  part  of  the  latter  undergo  an  interchange  of  elements. 

The  fluorine  uniting  with  boron  gives  rise  to  fluoboric  acid  gas  ; and 
by  the  union  of  calcium  and  oxygen,  lime  is  generated,  which  com- 
bines with  boracic  acid,  and  is  left  in  the  retort  as  borate  ol  lime. 

723.  Fluoboric  acid  gas  is  colourless,  has  a penetrating  pungent  Properties, 
odour,  and  extinguishes  flame  on  the  instant.  It  reddens  litmus 

paper  as  powerfully  as  sulphuric  acid,  and  forms  salts  with  alkalies 
which  are  called  jluolorates.  It  has  a singularly  great  affinity  for 
water.  When  mixed  with  air  or  any  gas  which  contains  watery  va- 
pour, a dense  white  cloud,  a combination  of  water  and  fluoboric  acid, 
appears,  thus  affording  an  extremely  delicate  test  of  the  presence  of 
moisture  in  gases.  Water  acts  powerfully  on  this  gas,  absorbing 
700  times  its  volume,  increasing  in  temperature  and  volume.  The 
solution  is  limpid,  fuming,  and  very  caustic. 

Fluoboric  acid  gas  does  not  act  on  glass,  but  attacks  animal  and 
vegetable  matters  with  energy,  converting  them,  like  sulphuric  acid, 
into  a carbonaceous  substance. 


* Phil.  Trans,  1812. 


208 


Chap.  HI. 


Procured. 


Theory. 


Properties. 


Singular 

appear- 

ance. 


Process. 


Another. 


Hydrogen  and  Nitrogen. 

Fluosilicic  Acid. 

Composition. 

Form.  Sp.  Gr.  Flu.  Si.  Equiv. 

Si+3F,  or  SiP3.  3.6111  56.04  3 eq.  4-22.5  1 eq.  = 78.54 

724.  Is  prepared  by  mixing  one  part  of  pounded  glass  with  an 
equal  weight  of  fluor  spar  and  two  parts  of  sulphuric  acid.  On  ap- 
plying a gentle  heat  fluosilicic  acid  gas  is  disengaged  with  efferves- 
cence, and  may  be  collected  over  mercury. 

725.  The  chemical  changes  are  differently  explained.  Regarding 
fluor  spar  as  a compound  of  fluoric  acid  and  lime,  the  former  is 
thought  to  unite  with  silicic  acid.  If  fluor  spar  is  regarded  as  a com- 
pound of  fluorine  and  calcium,  it  is  inferred  that,  by  the  action  of 
sulphuric  acid  on  fluoride  of  calcium,  hydrofluoric  acid  is  generated, 
and  that  the  elements  of  this  acid  react  on  those  of  silicic  acid,  and 
give  rise  to  water  and  fluosilicic  acid  gas  : the  gas  is  therefore  a flu- 
oride of  silicon. 

726.  It  is  a colourless  gas,  extinguishing  flame,  powerfully  irritat- 
ing, and  does  not  corrode  dry  glass.  Mixed  with  atmospheric  air  it 
forms  a white  cloud,  with  its  watery  vapour.  T.  244. 

727.  A singular  appearance  is  presented  when  the  beak  of  a re- 
tort, from  which  this  gas  is  escaping,  dips  into  water.  Each  globule 
of  the  gas,  as  it  comes  in  contact  with  the  water,  assumes  the  ap- 
pearance of  a vesicle,  a coating  of  silica  being  deposited  on  the 
external  surface  of  the  globule.  Small  tubes  appear  also  at  the 
beak  of  the  retort,  which  is  eventually  plugged  up,  so  that  it  is  ne- 
cessary at  last  to  remove  the  retort  altogether  till  they  are  taken 
away. 


COMPOUNDS  OF  SIMPLE  NON-METALLIC  ACIDIFIABLE  COM- 
BUSTIBLES WITH  EACH  OTHER. 


Section  XIV.  Hydrogen  and  Nitrogen — Ammoniacal  Gas. 

Com  position. 

Sijmb.  Sp.  Gr.  Hyd.  Nit.  Chem.  Equiv. 

N-I-3H,  or  NH3  0.5897  Air  =1  3.2050  3 eq.+15. 0325  14.15  1 eq.  By  Wght.17.15 
8-75  Hyd.=I  Vol.  200 

728.  This  gas  was  first  noticed  by  Priestley,  under  the  name  of 
alkaline  air  ; it  is  also  known  as  the  volatile  alkali,  but  more  usually 
by  the  name  ammoniacal  gas  or  ammonia. 

729.  Ammoniacal  gas  is  obtained  from  any  salt  of 
ammonia,  by  the  action  of  a pure  alkali  or  alkaline 
earth  : but  hydrochlorate  of  ammonia  and  lime  are 
generally  employed. 

Equal  parts  of  dry  slaked  lime,  each  separately  powdered, 
are  put  into  a small  glass  retort  or  gas  bottle,  and  upon  the  ap- 
plication of  gentle  heat  the  ammoniacal  gas  is  evolved,  and  is 
to  be  received  over  mercury. 

Persons  not  having  a mercurial  apparatus  may  receive  this 
gas  in  a glass  jar  inverted  over  a tube  bent  as  in  Fig.  168.  As 
the  gas  is  evolved  from  the  materials  contained  in  the  gas-bottle, 
it  rises  into  the  jar  and  displaces  the  atmospheric  air.  When 
the  jar  is  filled  with  ammonia  (which  will  be  known  by  its 
pungent  odour  as  it  escapes  from  the  neck  of  the  jar)  the  tube 


Ammonia. 


209 


may  be  carefully  withdrawn,  and  a well  ground  stopper  be  inserted  into  the  neck  Sect.  XIV. 
of  the  jar. 

The  gas  may  also  be  obtained  by  heating  common  liquid  ammo- 
nia (aqua  ammonias)  in  the  same  apparatus. 

730.  Ammonia  is  colourless,  has  A strong  pungent  odour,  and  acts  Properties, 
powerfully  on  the  eyes  and  nose.  It  is  quite  irrespirable  in  its  pure 

form,  but  when  diluted  with  air,  it  may*  be  taken  into  the  lungs  with 
safety.  Burning  bodies  are  extinguished  by  it,  nor  is  the  gas  in- 
flamed by  their  approach.  Ammonia,  however,  is  inflammable  in  a 
low  degree;  for  when  a lighted  candle  is  immersed  in  it,  the  flame 
is  somewhat  enlarged,  and  tinged  of  a pale  yellow  colour  at  the  mo- 
ment of  being  extinguished  ; and  a small  jet  of  the  gas  will  burn  in 
an  atmosphere  of  oxygen.  A mixture  of  ammoniacal  and  oxygen 
gases  detonates  by  the  electric  spark;  water  being  formed,  and  ni- 
trogen set  free. 

731.  When  an  electric  current  is  passed  through  a weak  solution  Action  of 
of  ammonia,  it  is  decomposed  by  the  secondary  action,  hydrogen  electricity” 
from  decomposed  water  being  evolved  at  the  negative  electrode,  and 
nitrogen  at  the  positive.^  But  if  a portion  of  mercury  form  the  ne- 
gative electrode,  no  hydrogen  is  evolved,  and  the  mercury  is  rapidly 
converted  into  a light  porous  substance,  which  has  the  lustre  and  all 

the  characters  of  an  amalgam.  As  soon  as  it  is  removed  from  the 
influence  of  the  electric  current,  rapid  decomposition  ensues,  mercury 
is  reproduced,  and  hydrogen  and  ammoniacal  gases  are  evolved  in 
the  ratio  of  one  measure  of  the  former  to  two  of  the  latter,  according 
to  the  observations  of  Gay-Lussac  and  Thenarcl.  The  production  of 
this  compound  is  explained  by  Berzelius  on  thd  supposition  that  am« 
monia,  by  uniting  with  an  additional  eq.  of  hydrogen,  forms  a com- 
pound, which  has  all  the  properties  of  a metal ; he,  therefore,  calls 
it  ammonium , The  oxide  of  ammonium,  the  composition  of  which  Ammoni- 
is  represented  by  the  formula  NH4-(-0,  he  considers  to  bo  the  base 
of  the  ammoniacal  salts,  t.  246. 

732.  Ammonical  gas  at  the  temperature  of  50°  an<|  under  a 
pressure  equal  to  6.5  atmospheres,  becomes  a transparerifcolourless 
liquid. 

Ammonia  has  all  the  properties  of  an  alkali  in  a very  marked  Alkaline, 
manner.  Thus  it  has  an  acrid  taste,  and  gives  a brown  stain  to  tur- 
meric paper  ; though  the  yellow  colour  soon  reappears  on  exposure 
to  the  air,  owing  to  the  volatility  of  the  alkali.  It  combines  also  with 
acids,  and  neutralizes  their  properties  completely. 

Its  affinity  for  water  may  be  shown  by  filling  a long  tube  with  the  gas,  and  Affinity  for 
opening  it  under  water;  the  ammonia  will  be  absorbed  with  great  rapidity,  and  water, 
completely  if  the  gas  is  pure.  According  to  Thomson  water  takes  up  780  times  Exp. 
its  bulk. 

Its  alkaline  character  may  be  shown  by  using,  instead  of  pure  water,  water  Exp. 
coloured  blue  by  litmus  or  cabbage,  or  yellow  by  turmeric. 

A piece  of  ice  passed  up  the  tube  standing  over  mercury,  is  rapidly  liquefied  Exp> 
and  the  gas  absorbed. t 

733.  None  of  the  ammoniacal  salts  can  sustain  a red  heat  without  Effect  of 
being  dissipated  in  vapour  or  decomposed,  a character  which  arises  eaU 


* Faraday,  Phil.  Tran e.  1834. 

t A vessel  of  water  or  mercury  should  be  at  hand  to  supply  the  loss  in  the  dish  in 
which  the  tube  is  placed  and  prevent  the  entrance  of  air. 

27 


210 


Chap.  III. 


Decompo- 

sition. 


Action  of 
chlorine, 


Phenomena 

attending. 

Exp. 


How  re- 
cognised. 


Exp. 


Liquor 

ammonise. 


Phillips’ 

process. 


Hydrogen  and  Nitrogen. 


from  the  volatile  nature  of  the  alkali.  If  combined  with  a volatile 
acid,  such  as  the  hydrochloric,  the  compound  itself  sublimes  un- 
changed by  heat. 

734.  Hydrogen  and  nitrogen  gases  do  not  unite  directly,  but  the 

composition  of  ammoniacal  gas  lias  been  determined  by  analysis 
with  electricity,  and  by  passing  it  through  red-hot  tubes.  If  passed 
over  a coil  of  iron  or  copper  wire  in  a red-hot  porcelain  tube,  the 
metals  become  brittle,  but  their  weight  is  not  altered.  The  expan- 
sion which  the  gas  suffers  in  being  thus  resolved  into  its  constituents, 
is  a singular  instance  of  change  of  properties  in  consequence  of  che- 
mical combination.  The  bladder  a,  (Fig.  169,)  is  filled  with  ammo- 
nia, which  may  be  F»e- 169- 

passed  through  the 
tube  b , in  the  furnace 
c,  the  hydrogen  and 
nitrogen  may  be  col- 
lected in  d. 

735.  Ammonia  is  decomposed  by  chlorine,  hydrochloric  acid  is 
formed  by  the  union  of  the  chlorine  with  its  hydrogen,  and  if  an  ex- 
cess of  the  gas  is  present,  hydrochlorate  of  ammonia  is  obtained. 

When  the  two  gases  are  suddenly  mixed  they  act  upon  each  other 
so  powerfully  as  sometimes  to  produce  detonation. 


Invert  a matrass  with  a conical  neck  and  wide  mouth,  over  another  Fig-  J'0. 
with  a taper  neck  containing  a mixture  of  sal  ammoniac  and  lime,  heat- 
ed  by  a lamp.  As  soon  as  the  upper  vessel  seems  to  be  full  of  ammonia,  ( 
by  the  overflow  of  the  pungent  gas,  it  is  to  be  cautiously  lifted  up,  and  \ J 
inserted,  in  a perpendicular  direction,  into  a wide  mouthed  glass  decan-  \ / 

ter,  or  flask,  nlled  with  chlorine.  On  seizing  the  vessels  thus  joined, 
with  the  two  hands,  covered  with  gloves,  and  suddenly  inverting  them  ijtt 
like  a sand-glass,  the  heavy  chlorine  and  light  ammonia,  rushing  in  op-  7\ 
posite  directions,  unite,  with  the  evolution  of  flame,  1 \ 

736.  Ammonia  is  readily  recognised  by  its  odour,  and  by  I \ 
the  white  fumes  which  are  given  off  when  a rod  dipped  in  ly 
hydrochloric  acid  is  brought  in  contact  with  it. 

This  will  be  evident  if  we  moisten  the  inside  of  a glass  jar  with 
hydrochloric  acid,  and  pass  into  it  a small  quantity  of  ammonia; 
dense  clouds  of  hydrochlorate  of  ammonia  will  immediately  form. 

737.  The  usual  state  in  which  ammonia  is  employed  is  in  solu- 

tion, both  in  chemistry  and  medicine.  This  solution  bears  the  name 
of  Aqua  Ammonice  in  the  Pharmacopoeia.  It  may  be  obtained  by 
passing  the  gas  into  water  in  a proper  apparatus,  (Fig.  171,)  or  by 
distilling  over  the  water  Fig.  m. 

and  gas  together. 

The  following  process, 
recommended  by  Phil- 
lips, answers  well. 

On  9 ounces  of  well  burn- 
ed lime  pour  half  a pint  of 
water,  and  when  it  has  re- 
mained in  a well  closed  ves- 
sel for  about  an  hour,  add  12 
ounces  of  hydrochlorate  of 
ammonia  in  powder  and  three  pints  and  a half  of  boiling  water ; when  the  mix- 
ture has  cooled,  pour  off  the  clear  portion,  and  distil  from  a retort  20  fluid  ounces. 


211 


Light  Carburetted  Hydrogen. 


The  sp,  gr.  of  this  solution,  which  is  sufficiently  strong  for  most  purposes,  is  Sect.  XV. 

0,954.* 

738.  Liquid  ammonia  should  be  preserved  in  well-stopped  glass  How  pre- 
bottles,  since  it  loses  ammonia  and  absorbs  carbonic  acid,  when  ex-  serve(L 
posed  to  air  ; when  heated  to  about  140°,  ammonia  is  rapidly  given 
off  by  it.  When  concentrated  it  requires  to  be  cooled  to  —40°  before 
it  congeals,  and  then  it  is  apparently  inodorous.! 


t 

Section  XV.  Compounds  of  Hydrogen  and  Carbon. 

739.  Two  compounds  of  hydrogen  and  carbon  have  long  been  Com- 
known,  and  late  researches  have  brought  to  light  others  of  much  in-  hydrogen 
terest.  They  are  remarkable  for  their  number  ; for  supplying  some  and  carbon, 
instructive  instances  of  isomerism;  for  their  tendency  to  unite  with 

and  even  neutralize  powerful  acids,  without,  in  their  uncombined 
state,  manifesting  any  ordinary  signs  of  alkalinity. 

740.  Several  of  them  are  particularly  distinguished  by  their  che-  Distin- 
mical  affinities  ; for  although  compound,  they  exhibit  in  their  com- 
binations  with  other  substances,  the  characteristics  of  an  element. 

They  have  hence  been  called  compound  radicals.  In  organic  che- 
mistry they  hold  a place  as  the  roots  or  radicals  of  the  various 
organic  products,  and  in  inorganic  chemistry  as  compounds  formed 

by  the  direct  union  of  two  elements.!  T. 

Light  Carburetted  Hydrogen. 

Composition. 

Form „ Sp.  Gr „ Hyd-  Carb.  Equiv.  Eq.Vol. 

H2C  0.5593  Air  = 1 2 + 6.12  ==  $.12  100 

8.12  Hyd.  ==  1 

741.  This  gas  is  sometimes  called  heavy  inflammable  air , the  in- 
flammable air  of  marshes , and  hydrocarburet.  It  is  generally  termed 
light  carburetted  hydrogen. 

It  may  be  collected,  mixed  however  with  carbonic  acid  and  nitro-  Collected, 
gen  gases,  by  stirring  the  bottom  of  almost  any  stagnant  pool  of 
water,  especially  if  formed  of  clay.  It  should  be  washed,  when  col- 
lected, with  lime  water  or  liquid  potassa,  to  remove  the  carbonic 


* Or  two  parts  of  lime  and  three  of  sal  ammoniac  may  be  mix-  Pig-  172. 

ed,  after  the  former  has  been  slaked  with  a half  of  its  weight  of 
water  and  allowed  to  cool  5 they  should  both  be  in  fine  powder, 
and  intimately  blended,  taking  care  to  avoid  the  pungent  fumes 
that  are  disengaged.  The  mixture  is  then  put  into  an  iron  retort 
and  placed  in  a sand  bath.  (Fig.  172.)  The  beak  6f  the  retort  is 
then  luted  to  a quilled  globe,  making  the  joining  tight  with  plas- 
ter*of-paris ; water,  equal  in  weight  to  £ of  the  salt  used,  is 
put  into  a bottle  or  receiver.  The  tube  from  the  globe  should 
reach  to  the  bottom  of  the  bottle,  which  should  not  be  more  than 
half  full,  when  the  proper  quantity  of  water  has  been  put  in. 

The  use  of  the  glass  globe  is  to  allow  air  to  pass  into  the  retort 
as  the  apparatus  becomes  cold,  and  prevent  any  of  the  water  of 
ammonia  from  being  carried  along  with  it ; for  when  the  gas  ceases  to  come  and  all 
the  liquid  in  the  bottle  has  been  forced  into  the  globe  by  the  pressure  of  the  atmos- 
phere, air  will  enter  by  the  quill  tube  and  pass  through  the  water  to  the  retort, 
t For  a table  of  the  quantity  of  ammonia  in  solutions,  see  Davy’s  Elements. 
t Those,  which  from  their  atomic  constitution,  or  from  being  the  products  of  the 
organic  kingdom,  belong  to  that  department,  will  be  described  under  that  division. 


Another  pro- 
cess- 


212 


Hydrogen  and  Carbon . 

Chap,  m.  acid,  of  which  it  contains  This  is  the  only  convenient 

method  of  obtaining  it. 

Properties.  742.  Light  carburetted  hydrogen  is  nearly  inodorous,  and  without 
colour  or  taste.  Water  absorbs  about  ^ of  its  volume.  It  does 
not  support  combustion  or  life,  but  is  highly  inflammable,  burning 
wit.h  a yellowish  flame. 

Detonation  743.  Mixed  with  atmospheric  air  it  may  be  kindled  by  a lighted 
with  air  taper,  and  explodes  with  violence,  provided  it  forms  not  less  than 
and  oxygen  0f  the  mixture,  and  does  not  exceed  With  oxygen  gas 
the  detonation  is  louder  and  more  violent ; but  it  is  necessary  that 
oxygen  should  rather  exceed  the  inflammable  gas  in  volume,  and  yet 
should  not  be  more  than  2^  times  its  bulk.  For  its  perfect  combus- 
tion more  than  twice  its  volume  of  oxygen  gas  is  required,  of  which 
exactly  two  volumes  are  consumed,  and  carbonic  acid  is  produced, 
equivalent  in  volume  to  the  inflammable  gas. 

744.  One  hundred  measures  of  carbonic  acid  gas,  contain  100  of 
carbon  vapour  and  100  of  oxygen,  just  half  the  oxygen  employed  ; 
the  remaining  oxygen  requires  200  measures  of  hydrogen  to  form 
water. 

Hence  at  G0°  F.  and  30  inches  barom. — 

100  cubic  inches  of  carbon  vapour  weigh  13.0714  grs. 

200  “ “ hydrogen  gas  . . 4.2734  “ 

100  “ “ light  carb.  hyd.  must  weigh  17.3448  “ 

being  in  the  ratio  of  2 to  6.12  and  the  sp.  gr.  ought  to  be  0.5593 

which  agrees  nearly  with  experiment.  T. 

745.  Chlorine  and  carburetted  hydrogen  do  not  act  on  each  other 
at  common  temperatures,  when  quite  dry,  even  if  they  are  exposed 
to  the  direct  solar  rays.  If  the  gases  are  moist,  and  the  mixture  is 
kept  in  a dark  place,  still  no  action  ensues  ; but  if  light  be  admitted 
decomposition  follows.  The  nature  of  the  products  depends  on  the 
proportion  of  the  gases.  If  4 measures  of  chlorine  and  1 of  carbu- 
retted hydrogen  are  present,  carbonic  and  hydrochloric  acid  gases 
will  be  produced.  When  three  measures  of  chlorine  are  present 
carbonic  oxide  is  formed,  one  half  less  water  being  decom- 
posed. H. 

746.  The  gaseous  matter  that  often  issues  in  large  quantity  from 
coal  mines,  between  beds  of  coal,  and  collects  in  the  mines  mixed  with  the  at- 
mospheric air,  forms  an  explosive  mixture  that  has  been  the  cause  of 
many  fatal  accidents  ; the  first  unprotected  light  that  approaches  sets 
fire  to  the  whole  mixture.  The  frequent  loss  of  life  from  the  explo- 

Fire  damp,  sion  of  this  fire  damp , led  Davy  to  the  construction  of  the  safety 
lamp.* 

Davy’s  ex-  747.  In  the  course  of  his  experiments  Davy  found  that  the  explo- 
periments.  sive  power  varies  with  the  proportions  of  carburetted  hydrogen  and 
air  ; thus  with  three  or  four  times  its  volume  of  air  there  is  no  ex- 
plosion, with  seven  or  eight  times  its  bulk  of  air  the  explosion  is 
powerful ; with  fourteen  times  its  volume  it  is  still  explosive,  but 
with  a larger  quantity  a taper  burns  in  the  mixture  only  with 


♦ For  a full  account  of  the  elaborate  experiments,  &c.  on  this  subject,  the  student  is 
referred  to  Davy’s  Essay  on  Flame , and  the  biographies  of  him  by  Paris  and  Dr 
Davy. 


Composi- 
tion and 
sp.  gr. 


Action  of 
chlorine. 


Present  in 


213 


Olefiant  Gas. 


Theory  of 
the  safety 
lamp, 


an  enlarged  flame.  He  also  ascertained  that  the  temperature  re-  Sect,  xv. 
quired  for"  explosion  was  very  high  ; and  that  flame  cannot  pass 
through  a narrow  tube,  or  a tissue  of  wire-gauze> 

748.  Flame  is  gaseous  matter  heated  so  intensely  as  to  be  luminous*  Flame 
When  it  comes  in  contact  with  the  sides  pf  minute  apertures,  as  when 
wire-gauze  is  held  upon  a burning  jet  of  coal  gas,  or  the  flame  of  a 
spirit  lamp,  it  is  deprived  of  so  much  heat  that  its  temperature  in- 
stantly falls  below  the  degree  at  which  gaseous  matter  is  luminous, 
though  the  gas  itself  passes  freely  through  the  interstices  and  is 

still  very  hot. 

This  will  be  seen  on  bringing  a frig-  Exp, 

piece  of  wire-gauze  down  upon  the 
flame  ; as  at  a,  (Fig.  173,)  the  gas 
will  be  found  to  pass  through  and 
may  be  ignited  above  the  gauze  as 
atB. 

749.  If  the  flame  of  a com- 
mon lamp  be  everywhere  pro- 
perly surrounded  with  a wire- 

gauze,  and  in  that  state  immersed  into  an  explosive  gaseous  mixture* 
it  will  be  inadequate  to  its  inflammation,  that  part  only  being  burned 
which  is  within  the  cage,  communication  to  the  inflammable  air 
without  being  prevented  by  the  cooling  power  of  the  metallic  tissue ; 
so  that  by  such  a lamp  the  explosive  mixture  will  be  consumed, 
but  hot  exploded. 

Fig.  174  is  a representation  of  the  safety  lamp,  a is  a cylinder  of 
wire-gauze,  with  a double  top,  securely  and  carefully  fastened,  by 
doubling  over  to  the  brass  rim  b , which  screws  on  the  lamp  c.  The 
whole  is  protected  and  rendered  convenient  for  carrying,  by  the 
frame  and  ring  d.  If  the  cylinder  be  of  twilled  wire-gauze,  the  wire 
should  be  at  least  of  the  thickness  of  one  fortieth  of  an  inch,  and  of 
iron  or  copper*  and  30  in  the  warp,  and  16  or  18  in 
the  weft.  If  of  plain  wire-gauze,  the  wire  should 
not  be  less  than  one  sixtieth  of  an  inch  in  thick- 
ness, and  from  28  to  30  both  warp  and  woof.* 

The  operation  of  this  lamp  may  be  shown  on 
a small  scale,  by  suspending  it  in  an  inverted  glass 
jar,  and  then  admitting  a sufficient  stream  of  coal 
gas  from  a gas-holder  by  a tube  entering  below,  (Fig.  175,)  to 
render  the  enclosed  atmosphere  explosive.  The  flame  of 
the  lamp  first  enlarges,  and  is  then  extinguished,  the  whole  of 
the  cage  being  filled  with  a lambent  blue  light  ;t  on  turning  off 
the  supply  of  the  gas  this  appearance  gradually  ceases,  and  the 
wick  becomes  rekindled,  when  the  atmosphere  returns  to  its 


Fig.  174. 

A 


Fig.  175, 


Illustrated. 


natural  state.! 


Form. 

2H+2C,  or  H (X 


Olefiant  Gas. 

Hyd. 


2 + 


Carb. 

12.24 


2 eq. 


Equiv. 
= 14.24 


Eq.  Vol. 
100 


Sp.  Gr. 

0 9808  Air  = l 
14.24  Hyd.  = 1 

750.  This  gas  was  discovered  in  1796,  by  some  associated  Dutch  Olefiant 
chemists,  and  was  termed  by  them  olefiant  gas , from  its  property  of  gas* 

* To  increase  the  safety  of  the  lamp  when  exposed  to  a strong  current  of  an  explo- 
sive atmosphere,  the  addition  of  a glass  cylinder  and  allowing  the  air  to  enter  only 
through  fine  apertures  below,  has  lately  been  resorted  to  with  success. 

t The  platinum  coil  within  will  continue  red-hot.  (257)'. 

t The  explosion  may  be  safely  exhibited,  previously,  by  suspending  the  lamp  with- 
out the  wire-gauze  cylinder  from  a piece  of  pasteboard  covering  the  jar,  and  admitting 
coal  or  oil  gas.  W. 


214 


Chap.  III. 

How  ob- 
tained. 

Process. 


Properties. 


Decompo-j 

sed. 

Action  of 
chlorine. 


Exp. 


Hydrosul- 

phuric 

acid. 


Processes- 


Hydrogen  and  Sulphur. 

forming  an  oily  looking  liquid  with  chlorine.  It  has  been  called  by 
Thomson  hydroguret  of  carbon. 

751.  It  is  usually  obtained  by  the  decomposition  of  alcohol  by 
sulphuric  acid. 

For  this  purpose  four  parts  of  the  acid  and  one  of  alcohol  are  put  into  a capa- 
cious retort,  and  heated  by  a lamp.  The  -acid  soon  acts  upon  the  alcohol, 
effervescence  ensues  and  olefiant  gas  passes  over.  The  retort  should  not  be 
more  than  one  third  full,  and  the  acid  and  alcohol  should  be  shaken  together 
before  the  heat  is  applied. 

A little  ether  is  formed  at  first,  the  solution  becomes  dark,  sulphu- 
rous acid  and  carbonic  oxide  are  formed,  and  carbon  deposited-* * * § 

752.  This  gas  is  colourless  and  inodorous.  Water  absorbs  about 
£ of  its  volume.  It  extinguishes  flame,  and  does  not  support  life. 
It  is  inflammable,  burning  with  a bright  yellowish  white  flame. 
When  mingled  with  oxygen  gas,  it  explodes  with  great  violence. 
One  part  by  volume  requires,  for  perfect  combustion,  three  of  oxygen  ; 
and  two  of  carbonic  acid  are  produced.  100  cubic  inches  weigh 
30.4162  by  calculation,  and  its  sp.  gr.  is  as  stated.! 

Olefiant  gas  is  decomposed  by  electricity,  and  by  transmission 
through  red-hot  tubes. 

753.  When  this  gas  is  mixed  with  chlorine,  in  the  proportion  of  1 
to  2 by  vol.  the  mixture,  on  inflammation,  produces  hydrochloric  acid, 
and  charcoal  is  abundantly  deposited. 

If  the  gases  be  well  mixed,  and  then  inflamed  in  a tall  and  narrow  glass  jar, 
(about  two  feet  high  and  four  inches  in  diameter),  placed  with  its  mouth  up- 
wards, the  experiment  is  very  striking;  a deep  flame  gradually  descends  through 
the  mixture,  and  a dense  black  cloud  of  carbon  rises  into  the  atmosphere  ; fumes 
of  hydrochloric  acid  are  at  the  same  time  formed,  and  a peculiar  aromatic  odour 
is  evolved. 

If  instead  of  inflaming  the  gases,  the  jar  be  inverted  in  a basin  of  water,  or  if 
they  be  mixed  in  a clean  and  dry  glass  globe  exhausted  of  air,  they  act  slowly 
upon  each  other,  and  a peculiar  fluid  is  formed,  which  appears  like  a heavy  oil  ; 
hence  the  name,  olefiant  gas.  B.  1.  321. 


Section  XVI.  Compounds  of  Hydrogen  and  Sulphur. 

Hydrosvlphuric  Acid — Sulphuretted  Hydrogen. 

Composition. 

Form.  Sp.  Gr.  Iiyd.  Sul.  Equiv.  Eq.  Vol. 

HS  I- 1782  Air  =1  l + 16.1  = 17-1  100 

17.10  Hyd.  = 1 

754.  This  gaseous  compound  of  sulphur  and  hydrogen  was  first 
investigated  by  Scheele  in  1777.  It  may  be  obtained  by  presenting 
sulphur  to  nascent  hydrogen,  which  is  the  case  when  protosulphuret 
of  iron  is  acted  upon  by  dilute  sulphuric  acid. 

The  sulphuret  of  iron  may  be  prepared  by  heating  a bar  of  iron  to  a white  or 
welding  heat,  and,  in  this  state,  rubbing  it  with  a roll  of  sulphur.  The  metal 
and  sulphur  unite,  and  form  a liquid  compound,  which  falls  down  in  drops.t 
These  soon  congeal ; and  the  compound  must  be  preserved  in  a well  closed  phial. 
Or  a mixture  of  two  parts  of  iron  filings  and  rather  more  than  one  part  of  sulphur, 
may  be  heated  to  redness  in  a covered  crucible. § A portion  of  this  may  be  in 


* The  changes  are  complicated ; for  the  theory,  see  Alcohol, 

i Its  density  by  experiment  is  0.97.  (Thomson.) 

t They  should  be  received  in  an  iron  basin  filled  with  water. 

§ The  gas  which  this  affords  is  mixed  with  a good  deal  of  hydrogen  gas- 


Hydrosulpharic  Acid . 215 

troduced  into  a retort  or  gas  bottle  and  diluted  sulphuric  acid  poured  upon  it,  as  sect.  XVI. 
in  the  process  for  obtaining  hydrogen  gas  (378).  It  may  also  be  conveniently  “ : ^ 

obtained  from  bruised  sesquisulphuret  of  antimony  (crude  antimony  of  the  shops) 
with  five  or  six  times  its  weight  of  hydrochloric  acid  (sp.gr.  1.160  or  thereabouts) 
contained  in  a retort  or  gas  bottle,  and  heated  by  a lamp. 

755.  In  the  first  process  the  sulphuret  and  water  interchange  ele-  Theories, 
ments,  hydrosulpharic  acid  and  protoxide  of  iron  are  generated ; the 

latter  unites  with  sulphuric  acid  and  the  former  escapes. 

In  the  process  with  antimony  the  elements  concerned  are — 

1 eq.  sesquisulphuret  and  3 eq.  hydrochloric  acid 
2Sb+3S  3(H+C1) 

which  yield 

3 eq.  hydrosulphuric  acid  and  L eq.  sesquichloride  of  antimony 
3(H+S)  2Sb+3Cl 

756.  The  gas  may  be  collected  over  water,  though,  by  agitation,  Absorbed 
that  fluid  absorbs  nearly  thrice  its  bulk  ; it  should  be  received  into  by  water' 
bottles  provided  with  glass  stoppers,  and  after  filling  them  entirely 

with  the  gas,  the  stopper  should  be  introduced. 

757.  Faraday  obtained  it  in  a liquid  form  by  producing  it  under  Liquefac- 
pressure.  It  was  colourless,  limpid,  and  with  a refractive  power  tion  of  sul- 
greater  than  that  of  water.  The  pressure  of  its  vapour  was  nearly  hydrogen 
equal  to  17  atmospheres  at  the  temperature  of  50°  F.  Its  specific 
gravity  appeared  to  be  0.9. 

758.  When  in  the  form  of  gas,  the  smell  is  extremely  offensive,  Properties, 
resembling  that  of  putrefying  eggs,  or  of  the  washings  of  a gun- 
barrel,  to  which  indeed  it  imparts  their  offensive  odour.  It  exists  in 

some  mineral  waters. 

759.  It  appears  to  be  one  of  the  most  unrespirable  of  all  the  gases,  Unrespira- 
for  a small  bird  died  immediately  in  air  containing  x of  its  vo- ble’ 
lume  of  hydrosulphuric  acid  gas ; a dog  perished  in  air  mingled  with 

■g-^,  and  a horse  in  air  containing 

760.  It  tarnishes  silver,  mercury,  and  other  polished  metals,  and  Action  on 
instantly  blackens  white  paint  and  solution  of  acetate  of  lead.  By  metals, 
direct  experiments,  Henry  has  found  that  one  measure  of  this  gas, 
mixed  with  20.000  measures  of  hydrogen,  or  of  carburetted  hydro- 
gen, or  common  air,  produces  a sensible  discoloration  of  white  lead, 

or  of  oxide  of  bismuth,  mixed  with  water,  and  spread  upon  a piece  of 
card. 

761.  It  is  inflammable,  burning  with  a pale  blue  flame,  but  does  inflnmma- 
not  support  the  combustion  of  other  bodies.  Water  and  sulphurous  ble. 
acid  are  the  products  of  its  combustion,  and  sulphur  is  deposited. 

762.  Hydrosulphuric  acid  contains  its  own  vol.  of  hydrogen  gas,  Coinposi- 

and  16.66  of  the  vapour  of  sulphur;  and  since  tion- 

16.66  cub.  inches  of  the  vapour  of  sulphur  weigh  . . 34.4012  grs. 

100  ^ “ hydrogen  gas  “ . . 2.1367 

100  “ “ hydrosulphuric  acid  gas  must  weigh  . 36.5379  T. 

763.  The  salts  of  hydrosulphuric  acid  are  called  hydrosulphates  or  Salts  of. 
hydrosulphurets.  They  are  decomposed  by  sulphuric  or  hydrochlo- 
ric acids.  This  acid  rarely  unites  directly  with  metallic  oxides  ; but  in 

most  cases  its  hydrogen  combines  with  the  oxygen  of  the  oxide,  and 
its  sulphur  with  the  metal. 


*Thenard,  iii.  601. 


216 


Chap.  III. 
Use. 


Solution 

decompo- 

sed. 


Process. 


Theory. 


Properties. 


Composi- 

tion. 


Hydrogen  and  Sulphur. 

764.  Hydrosulphuric  acid,  both  in  the  state  of  a gas  and  of  watery 
solution,  precipitates  most  metallic  solutions,  and  is  hence  an  ex- 
ceedingly delicate  test  of  the  presence  of  most  of  the  metals. 

Water  impregnated  with  this  gas,  when  exposed  to  the  atmos^ 
phere,  becomes  covered  with  a pellicle  of  sulphur.  Sulphur  is  even 
deposited  when  the  water  is  kept  in  well  closed  bottles. 

Chlorine,  iodine  and  bromine  decompose  it  with  separation  of  suh 
phur,  and  an  atmosphere  charged  with  the  gas  may  be  speedily  pu- 
rified by  chlorine. 

Per sulphur et  of  Hydrogen. 

Composition. 

Form.  Hydr.  Sulph.  Equiv. 

HS2  • 1 1 eq.  + 32.2  2 eq.  — 33.2 

765.  This  compound  was  discovered  by  Scheele  and  described  by 
Berthollet.*  When  protosulphuret  of  potassium  (or  of  any  metal 
of  the  alkalies  and  alkaline  earths)  is  mixed  in  solution  with  sul- 
phuric acid,  the  oxygen  of  water  unites  with  potassium  and  its  hy- 
drogen with  sulphur.! 

7 66.  Persulphuret  of  hydrogen  is  conveniently  made  by  boiling  equal  parts 
of  recently  slaked  lime  and  flowers  of  sulphur  with  5 or  6 parts  of  water  for 
half  an  hour,  when  a deep  orange-yellow  solution  is  formed,  which  contains 
persulphuret  of  calcium.  Let  this  liquid  be  filtered,  and  gradually  added  cold 
to  an  excess  of  hydrochloric  acid  diluted  with  about  twice  its  weight  of  water, 
stirring  it  briskly.  A copious  deposit  of  sulphur  falls  (the  Sulphur  Pracipitatuvn 
of  the  Lond.  Pharmacop.)  and  persulphuret  of  hydrogen  gradually  subsides  in 
the  form  of  a yellowish  semi-fluid  matter  like  oil. 

767.  The  change  which  ensues  in  the  formation  of  the  yellow  so- 
lution may  be  theoretically  represented  thus  : — 

2 eq.  lime  and  6 eq.  sulph.  2 1 eq.  hyposulphs.  acid  and  2 eq.  bisulphuret  of  calcium. 
2(Ca+0)  6S  .2  2S+20  2(Ca+2S). 

The  hyposulphurous  acid  exists  in  solution  united  with  lime,  and  is 
decomposed  when  hydrochloric  acid  is  added,  resolving  itself  into 
sulphurous  acid  and  sulphur. 

76S.  At  common  temperatures  it  is  a viscid  liquid  of  a yellow 
colour,  with  a density  of  about  1.769,  and  a consistence  varying  be- 
tween that  of  a volatile  and  fixed  oil.  It  has  the  peculiar  odour 
and  taste  of  hydrosulphuric  acid,  though  in  a less  degree.  Its  ele- 
ments are  so  feebly  united,  that  in  the  cold  it  gradually  resolves  it- 
self into  sulphur  and  hydrosulphuric  acid,  and  suffers  the  same 
change  instantly  by  a heat  considerably  short  of  212°  F.  Decom- 
position is  also  produced  by  the  contact  of  most  substances,  especial- 
ly of  metals  and  oxides. 

769.  The  composition  of  persulphuret  of  hydrogen  has  been  va- 
riously stated.  According  to  Dalton  it  is  a bisulphuret.  But  The- 
nard  found  its  constituents  to  vary;  whence  it  is  probable  that  hy- 
drogen is  capable  of  uniting  with  sulphur  in  several  proportions.  It 
is  sometimes  regarded  as  an  acid. 


* Ann.  de  Chim.  xxv. 


t See  Turner,  254. 


Phosphuretted  Hydrogen. 


217 


Section  XVI L Hydrogen  and  Selenium. 

Seleniuretted  Hydrogen. 

770.  These  bodies  combine  to  form  a gaseous  compound  termed  Seleniuret- 
seleniuretted  hydrogen  or  hydroselenic  acid.  It  may  be  obtained  by  ted  hydrog. 
"dissolving  protoseleniuret  of  iron  in  hydrochloric  acid. 

771.  It  is  a colourless  gas,  highly  irritating  to  the  lining  mem-  Properties, 
brane  of  the  nose,  and  for  a time  destroying  the  power  of  smelling. 

Its  solution  smells  and  tastes  somewhat  like  hydrosulphuric  acid  ; it 
reddens  litmus  and  tinges  the  skin  brown.  It  is  decomposed  by  the 
air,  nitric  acid  and  chlorine,  and  selenium  is  deposited.  It  occa- 
sions precipitates  in  solutions  of  neutral  metallic  salts,  which  are 
black  or  dark  brown,  with  the  exception  of  those  from  zinc,  manga- 
nese and  cerium,  which  are  flesh-coloured. 

772.  Seleniuretted  hydrogen  is  easily  decomposed  by  the  action  ^edcompo’ 
of  air  and  water  ; it  is  absorbed  by  moist  substances  and  communi- 
cates to  them  a red  colour.  The  selenium  is  thus  remarkably  de- 
posited throughout  the  texture  of  organic  bodies.  A piece  of  moist 

paper  is  penetrated  by  the  red  colour.  Moist  wood  and  even  a thin 
piece  of  caoutchouc  became  in  the  same  way  red  throughout.  B.  292. 

Hydroselenic  acid  consists  of  39.6  or  1 eq.  of  selenium  and  I of 
hydrogen  ; its  equiv.  is  40.6  and  its  formula  H-f-Se  or  HSe. 

Section  XVIII.  Compounds  of  Hydrogen  and  Phosphorus. 

773.  The  two  compounds  of  hydrogen  and  phosphorus  which ^ und  s°m ' 
have  heretofore  been  known  as  phosphuretted  and  perphosphuretted 
hydrogen,  have  been  found  by  Rose  to  be  isomeric,  identical  in  com- 
position, and  to  differ  only  by  the  one  being  spontaneously  inflam- 
mable and  the  other  not  so.  Leverrier*  has  proved  that  perphosphu- 
retted hydrogen  is  a mixture  of  phosphuretted  hydrogen  with  about 

fjy  of  its  volume  of  a spontaneously  inflammable  compound  of  31.4' g^  ^ 
parts  or  2 eq.  of  phosphorus,  and  2 parts  or  2 eq.  of  hydrogen.  In  ^yd. 
the  same  paper  he  establishes  the  existence  of  a solid  compound  of 
2 eq.  of  phosphorus  and  1 eq.  of  hydrogen.  The  latter  is  deposited 
on  the  sides  of  the  glass  vessel  when  moist  phosphuretted  hydrogen 
gas,  recently  prepared,  is  exposed  to  strong  light. 

Phosphuretted  Hydrogen. 

tSyrrib.  Density . Equiv.  Eq.  V'ol. 

2P+3H  or  P2H3  1.1850  34.4  200 

774.  Phosphuretted  hydrogen  was  discovered  by  Davy  in  1S12,  oiseovery, 
by  heating  hydrated  phosphorous  acid  in  a retort  ; and  it  &c. 

is  evolved  from  hydrous  hypophosphorous  acid  by  similar  treat- 
ment. It  is  also  formed,  according  to  Dumas,  by  the  action  of 
strong  hydrochloric  acid  on  phosphuret  of  calcium. 

775.  It  may  also  be  obtained,  in  an  impure  state,  by  boiling  phos-  procegs 
phorus  with  a solution  of  potassa,  or  milk  of  lime.  Water  is  de- 
composed, the  oxygen  and  hydrogen  of  which  unite  with  different 
portions  of  phosphorus,  and  phosphoric  acid,  hypophosphorous  acid, 

and  phosphuretted  hydrogen  are  generated. 

* See  the  papers  of  Dumas,  Buff,  Rose,  and  Graham,  in  An • de  Ch.  ei  de  Phys. 
xxxi.  113,  xli.  220,  and  xli.  5,  Phil.  Mag.  v.  401. 


218 


Chap-  III. 

Explodes 
with  air, 
&c. 


Process. 


Another. 


Properties. 


Mitchell’s 
method  of  pre- 
paring phos- 
phuret  of  catct- 

Uffl, 


Hydrogen  and  Phosphorus. 

776.  When  the  gas  is  obtained  pure  from  hydrated  phosphorous  or 
hypophosphorous  acids,  it  may  be  mixed  with  air  or  oxygen  gas  at 
common  temperatures  without  danger ; but  the  mixture  detonates 
with  the  electric  spark  or  at  a temperature  of  300°.  Even  dimin- 
ished pressure  causes  an  explosion,  an  effect  which  in  operating 
with  the  mercurial  trough  is  produced  simply  by  raising  the  tube,  so 
that  the  level  of  the  mercury  within  may  be  a few  inches  higher 
than  at  the  outside. 

777.  In  preparing  the  gas  from  phosphorus  and  solution  of  po- 
tassa  in  a glass  retort,  the  atmospheric  air  should  be  removed,  other- 
wise explosion  may  occur. 

A retort  holding  a pint  may  be  employed.  About  a quarter  of  an  ounce  of 
phosphorus  may  be  placed  in  the  retort  and  a moderately  strong  solution  ofpotas- 
sa  poured  upon  it  until  the  neck  and  body  of 
the  retort  are  completely  filled.  The  finger 
being  placed  over  the  beak  it  is  next  immersed 
under  the  surface  of  a portion  of  the  same  so- 
lution, contained  in  a glass  dish  or  a small 
pneumatic  trough,  and  the  finger  is  then 
removed.  The  retort  may  be  attached  to  a 
block  of  wood  or  supported  securely  upon  the 
rings  of  a retort  stand.  (Fig.  17G.)  The  su- 
perfluous solution  may  then  be  removed  by  passing  up  hydrogen  gas.*  The 
neat  of  a lamp  is  carefully  applied  and  soon  after  the  solution  boils,  the  gas 
is  evolved  in  abundance,  and  inflames  on  escaping  into  the  air. 

Forty  grains  of  phosphorus,  fifty  of  caustic  potassa,  and  sixty 
drops  of  water,  give  this  gas  very  readily  when  gently  heated  in  a 
small  retort,  (capable  of  holding  an  ounce  and  a half  or  two  ounces 
when  quite  full,)  and  with  very  little  trouble. 

The  readiest  mode  of  procuring  this  gas  is  by  means  of  phosphu- 
ret  of  calcium  ;t  lumps  of  which  may  be  dropped  into  water  acid- 
ulated with  hydrochloric  acid.  The  retort  or  gas  bottle  may  be 
placed  wholly  beneath  the  water  in  the  pneumatic  trough,  and  the 
combustion  of  the  bubbles  of  gas  will  take  place  at  the  surface. 

778.  This  gas  is  colourless,  has  a nauseous  odour  like  onions,  a 
very  bitter  taste,  and  inflames  when  mixed  with  air,  a property 


* This  may  be  done  from  a gas  bottle  having  a long  and  slender  leaden  pipe  at- 
tached to  it,  or  by  a pipe  and  flexible  tube  proceeding  from  the  apparatus  (Fig.  120.) 
It  will  be  found  necessary  after  all  the  solution  has  been  expelled  from  the  neck  to 
incline  the  body  of  the  retort  so  as  to  allow  a part  of  what  remains  in  the  body  to 
flow  into  it,  which  is  to  be  expelled  as  at  first. 

A very  simple  method  of  avoiding  all  danger,  is  to  moisten  the  interior  of  the  re- 
tort with  ether. 

t.The  following  method  of  obtaining  this  compound  has  been  described  by  Mitchell.* 
I employ  two  Hessian  crucibles,  some  of  the  inner  members  of  a nest.  The  larger  of 
the  two  has  a hole  bored  through  its  bottom,  and  a test  tube  of  a suitable  size  luted 
in  with  clay.  The  phosphorus  is  put  into  the  test  tube  ; the  top  of  which  is  loosely 
covered  with  a piece  of  broken  crucible  to  prevent  the  pieces  of  quicklime  from  running 
down  into  it.  The  lime  is  then  put  in  so  as  to  fill  this  crucible  and  partly  fill  the  upper 
one,  which  serves  as  a cover  to  it,  and  is  luted  on  with  some  fine  clay  a little  moisten- 
ed. The  cover  has  also  a small  hole  in  its  top  to  afford  an  outlet  for  the  air,  &c.  The 
whole  is  placed  upon  the  grate  of  a furnace,  with  the  test  tube  projecting  through  it 
below,  and  a charcoal  fire  is  kindled  around  it.  The  phosphorus  may  be  kept  cool,  if 
necessary,  by  making  the  tube  dip  into  water  contained  in  a tin  cup  attached  to 
the  end  of  a stick.  When  the  crucibles  and  contents  are  thoroughly  red-hot,  a chafing 
dish  is  substituted  for  the  tin  cup,  and  the  phosphorus  rising  in  vapour  produces  the 
desired  change.  The  phosphuret  should  be  preserved  in  a sealed  phial. 

* Mitchell  in  Jimer.  Jour.  xvii.  349, 


Fig.  176. 


219 


Cyanogen  Gas , 

which  it  loses  by  being  kept  over  water ; water  takes  up  two  per 
cent,  of  the  gas,  and  acquires  a bitter  taste  and  the  smell  of  onions. 

779.  If  the  beak  of  the  retort  (776)  is  plunged  under  water,  the 
successive  bubbles  of  gas  as  they  escape,  burst  into  flame  and  form 
rings  of  dense  white  smoke  which  enlarge  as  they  ascend,  retaining 
their  shape  if  the  air  is  tranquil.  The  wreaths  are  formed  of  meta- 
phosphoric  acid  and  water. 

780.  When  bubbles  of  phosphuretted  hydrogen  are  let  up  into  a 
jar  of  oxygen,  they  burn  with  greatly  increased  splendour. 

They  should  be  received  in  a large  jar,  but  half  filled  with  oxygen,  and  care 
must  be  taken  not  to  allow  them  to  accumulate  in  the  jar.  The  safest  me- 
thod is  to  collect  a few  bubbles  in  a small  phial  and  pass  them  up  from  that  into 
the  large  jar,  a bubble  at  a time.  Similar  experiments  may  be  made  with  chlo- 
rine. 

781.  One  hundred  measures  of  phosphuretted  hydrogen  gas  con- 
tain 150  of  hydrogen  and  2 5 of  vapour  of  phosphorus,  hence  as 

150  eub.  inches  of  hydrogen  gas  weigh  ....  3.2050  grs. 

25  “ “ phosphorus  vapour  ....  33.5461  “ 

]00  “ “ phosphuretted  hydrogen  gas  should  weigh  36.7511 

and  its  calculated  density  should  be  1.1850,  which  is  nearly  a mean 
of  the  observations  of  Dumas  and  Rose. 

782.  According  to  Leverrier,  it  is  probable  that  the  compound  of 
phosphorus  and  hydrogen  composed  of  two  equiv.  of  each  of  its  ele- 
ments, which  is  spontaneously  inflammable,  communicates  that  pro- 
perty to  phosphuretted  hydrogen  gas.  This  opinion  is  grounded  on 
the  fact  that  when  spontaneously  inflammable  phosphuretted  hydro- 
gen is  kept  for  any  length  of  time  in  the  dark  it  suffers  no  change, 
but  in  a strong  light,  solid  phosphuretted  hydrogen  is  deposited,  and 
the  residual  gas  is  no  longer  spontaneously  inflammable.  Thus  it 
appears  that  by  the  action  of  light  P2H2  is  decomposed,  and  P2H 
and  P2H3  are  formed.  T.  258. 

Section  XIX.  Compounds  of  Nitrogen  and  Carbon. 

Bicarburet  of  Nitrogen-— Cyanogen  Gas . 

Composition. 

Form,.  Sp.  Gr.  Nit.  Car.  Equiv. 

N+2C,  or  NC2,  or  Cy.  1,8157  Air  = 1 14.15  1 eq.  12.24  2 eq.  26.39  by  Wght. 

25.39  Hyd.  =1  100  “ Vol. 

783.  This  gaseous  compound  was  discovered  by  Gay-Lussac,  in 
1815, ^ and  was  called  cyanogen  from  yvavos,  blue , and  yew&oj,  I ge- 
nerate, because  it  is  an  essential  ingredient  of  Prussian  blue. 

784.  It  is  obtained  by  heating  dried  bicyanuret  of  mercury  in  a 
small  glass  retort!  This  cyanpret,  formerly  called  prussiate  of 
mercury , is  composed  of  metallic  mercury  and  cyanogen.  On  expo- 
sure to  a low  red  heat,  it  is. resolved  into  its  elements;  the  cyanogen 
passes  over  in  the  form  of  gas,  and  the  metallic  mercury  is  sublimed. 
The  heat  applied  should  be  sufficient  to  expel  the  cyanogen  slowly 
and  steadily,  as  it  is  liable  ;to  be  decomposed  by  a high  temperature. 
Towards  the  end  of  the  process,  a black  substance  is  procured,  aris- 


Sect.  XIX. 


Rings. 


Combus- 
tion in  ox- 
ygen. 

Exp. 


Composi- 
tion and 
density. 


Effect  of 
light. 


Cyanogen. 


Process. 


* Ann.  de  Ckim.  xcv. 

t For  the  method  of  preparing  :tjiis  cyanu.ret,  see  Mercury. 


220 


Nitrogen  and  Carbon. 

Chap  hi.  ing  from  the  decomposition  of  part  of  the  cyanogen,  consisting  of  the 
same  ingredients  as  the  gas  itself.  T. 

Properties.  785.  Cyanogen  has  a strong,  penetrating,  and  disagreeable  smell, 
resembling  that  of  bitter  almonds.  It  burns  with  a bluish  flame 
mixed  with  purple,  which  can  be  shown  by  igniting  it  at  the  beak  of 
the  retort,  which  may  be  drawn  out  to  a fine  point  before  the  blow-pipe. 

786.  It  must  be  collected  over  mercury,  as  water  absorbs  4.5  times 
° ected.  vo|ume  0f  t|ie  gas.  ^he  aqueous  solution  reddens  litmus  paper, 

an  effect,  however,  not  to  be  ascribed  to  the  gas,  but  to  acids  ge- 
nerated by  the  mutual  decomposition  of  cyanogen  and  water. 

787.  Cyanogen  contains  its  own  bulk  of  nitrogen  and  twice  its 
volume  of  the  vapour  of  carbon  ; and  since 

100  cubic  inches  of  nitrogen  gas  weigh  . . . 30.1650  grs. 

200  “ “ vapour  of  carbon  “ ...  26.1428  “ 

100  “ “ cyanogen  gas  must  weigh  . . 56.3078  “ 

The  ratio  ofits  elements  by  weight  is, 

Nitrogen  30.1650  . . . 0.9727  14.15  1 eq. 

Carbon  26.1428  . . . 0 8430(2+0.4215)  . . . 12.24  2 eq. 

Sp.  gr.  The  sp.  gr.  of  a gas  so  constituted  is  0.9727-f-0.843= 1.8157,  which 
is  near  1.8064  the  number  found  experimentally  by  Gay-Lussac. 

Cyanogen  is  a bicarburet  of  nitrogen  ; but  its  most  convenient 
name,  cyanogen , may  be  expressed  by  Cy.*  t.  259. 


Section  XX.  Compounds  of  Sulphur  with  Carbon , fyc. 


Bisulphuret  of  Carbon. 

Composition. 


Carbon  and 
sulphur,  bi- 
sulphuret, 
or  alcohol 
of  sulphur. 
How  ob- 
tained. 


Properties, 


Form.  Carb.  Sul.  Equiv.  Eq.  Vol. 

C+2SorCS2  6.12  + 32.2  = 38.32  100 

788.  This  substance  was  discovered  in  1796  by  Larnpadius  who 
regarded  it  as  a compound  of  sulphur  and  hydrogen,  and  termed  it 
alcohol  of  sulphur. 

789.  It  may  be  obtained  by  heating  in  close  vessels  the  native  bi- 
sulphuret of  iron  (iron  pyrites)  with  one  fifth  of  its  weight  of  well 
dried  charcoal,  or  by  passing  the  vapour  of  sulphur  over  fragments 
of  charcoal  heated  to  redness  in  a tube  of  porcelain.! 

790.  The  bi-sulphuret  of  carbon  is  eminently  transparent,  and 
perfectly  colourless.  Sometimes,  immediately  after  distillation,  the 


* Paracyanogen.  Symb.  N4C8.  Eq.  105.56?  The  brown  matter  left  in  the  retort 
in  the  foregoing  process  (784)  is  a solid  bicarburet  of  nitrogen,  isomeric  with  cyanogen, 
but  differing  from  it  in  its  physical  and  chemical  relations.  Heated  in  the  open  air, 
several  definite  compounds  of  carbon  and  nitrogen  may  be  obtained.*  It  is  soluble  in 
nitric  and  sulphuric  acids  and  forms  a compound  with  oxygen  in  which  one  eq.  of  ox- 
ygen is  combined  with  four  eq.  of  nitrogen  and  eight  eq.  of  carbon. 

Mellon.  Symb.  N4C6.  Eq.  93.32.  It  is  a lemon  yellow  coloured  Dowder,  insolur 
ble  in  water  and  alcohol,  but  soluble  and  decomposable  by  acids  ana  alkalies.  By 
heat  it  affords  one  vol.  of  nitrogen  and  three  of  cyanogen.  It  is  one  of  the  compound 
radicals.  T. 

Compound  of  Phosphorus  and  Nitrogen. 

Phosphuret  of  Nitrogen.  Symb.  N+2P,  or  NP2.  Eq.  45.55.  When  either  of  the 
chlorides  of  phosphorus  is  saturated  with  dry  amrnoniacal  gas,  a white  solid  mass  is 
obtained,  which  on  exposure  to  a strong  heat,  gives  rise  to  the  formation  of  phosphuret 
of  nitrogen,  and  hydrochloric  acid  gas.  It  is  a light  snow  white  powder,  insoluble  in 
water.  It  is  composed  of  31.4  parts  or  2 eq.  of  phosphorus,  and  14.15  or  one  eq.  of 
nitrogen. 

t A porcelain  tube  an  inch  or  more  in  diameter  is  coated  with  clay  and  wrapped  round 
• Brewster1*  Jour.  N.  S.  1.  75. 


221 


Sulphuret  of  Phosphorus. 

oily  liquid  appears  a little  opaque  and  milky  ; but  the  next  day  it  is  Sect,  xx. 
found  to  have  become  completely  limpid.  It  has  an  acrid,  pungent, 
and  somewhat  aromatic  taste ; its  smell  is  nauseous  and  fetid.  It  is 
soluble  in  alcohol  and  ether  ; its  refractive  power  in  regard  to  light 
is  very  considerable.  Its  sp.  gr.  is  1.272 ; of  its  vapour  2.668.  It 
boils  at  110°,  and  does  not  freeze  at — 60°.  It  is  very  volatile,  and 
the  cold  which  it  produces  during  evaporation  is  so  intense,  that  by 
exposing  a thermometer  bulb,  covered  with  fine  lint,  moistened  with 
it,  in  the  receiver  of  an  air-pump,  the  temperature  sunk,  after  ex- 
haustion to  —80°.  When  a mercurial  thermometer  is  used,  the 
metal  freezes.  When  a few  drops  of  this  liquid  are  poured  on  the 
surface  of  a glass  of  water,  the  temperature  of  which  is  32°  F. 
plumose  branches  of  ice  dart  to  the  bottom  of  the  vessel,  and  the 
whole  water  is  suddenly  frozen.  At  the  same  time,  the  sulphuret 
becomes  volatilized ; and  the  spiculae  of  ice  beautifully  exhibit  the 
colours  of  the  solar  spectrum. 

791.  Bisulphuret  of  carbon  is  a sulphur-acid,  that  is,  it  unites  with  A su]phur. 
sulphur  bases  to  constitute  compounds  analogous  to  ordinary  salts,  acid, 
and  hence  called  sulphur-salts.  Thus  bisulphuret  of  carbon  unites 

with  sulphuret  of  potassium,  forming  a sulphur  salt,  in  which  the 
former  acts  as  an  acid  and  the  latter  as  a base.  T. 

Sulphuret  of  Phosphorus . 

792.  Sulphur  and  fused  phosphorus  unite  frequently  with  vio-process 
lence.  The  experiment  should  not  be  made  with  more  than  30  or 

40  grs.  of  phosphorus.  The  phosphorus  is  placed  in  a glass  tube  5 
or  6 inches  long,  and  about  half  an  inch  wide,  when  by  a gentle 
heat  it  is  liquefied,  the  sulphur  is  added  in  successive  small  portions. 

The  compound  is  highly  combustible.* * 

with  iron  wire.  It  is  then  filled  with  frag-  Fig.  177. 

ments  of  charcoal,  taking  care  to  leave 
room  for  the  passage  of  vapour,  and  made 
to  traverse  a furnace  as  represented  in  Fig. 

177.  A retort  filled  about  a third  full  of 
sulphur  is  then  fitted  to  one  end  of  the  tube, 
supporting  it  by  a retort  stand,  and  using  a 
mixture  of  clay  and  sand  to  make  the  join- 
ing air-tight.  A bent  glass  tube  about  half 
an  inch  or  rather  less  in  diameter  is  attach- 
ed in  the  same  manner  to  the  ether  extre- 
mity of  the  porcelain  tube,  anci  connected 
with  a glass  globe  terminating  in  a small 
tube  placed  in  a receiver  half  full  of  water, 
which  must  be  kept  cold. 

When  everything  has  been  properly  ad- 
justed, fire  is  put  into  the  furnace,  and  the  tube  with  the  charcoal  brought  gradually 
to  a strong  red  heat.  The  sulphur  in  the  retort  is  then  made  to  pass  over  it  in  vapour, 
and  as  they  combine,  the  bisulphuret  which  is  formed  condenses  in  drops  that  fall  to 
the  bottom  of  the  water  in  the  receiver.  The  use  of  the  globe  is  to  prevent  any  water 
passing  back  to  the  porcelain  tube.  The  charcoal  should  be  well  prepared,  and 
not  mixed  with  any  unchanged  woody  fibre.  Reid. 

* Bisulphuret  of  Selenium  is  of  an  orange  colour,  and  fuses  at  a heat  a little  above 
212°.  Selenium  also  combines  with  phosphorus  and  forms  a seleniuret  which  is  very 
fusible. 

Sulphuret  of  Nitrogen  is  formed  by  the  reaction  of  chloride  of  sulphur  on  a solu- 
tion of  ammonia,  aud  contains  from  92  to  93  percent,  of  sulphur,  and  7 to  8 of  ni- 
trogen. 

Seleniuret  of  Phosphorus  may  be  made  in  the  same  manner  as  sulphuret  of  phos- 
phorus. It  is  very  fusible  and  decomposes  water  when  digested  in  it. 

Sulphuret  of  Nitrogen  is  formed  by  the  reaction  of  chloride  of  sulphur  on  a solu- 


222 


Metals. 


Chap.  IV. 


Number. 


CHAPTER  IV. 

METALS. 

Section  I.  General  Properties , and  Combinations. 

793.  Many  of  the  metals  have  been  long  known,  while  some  have 
been  recently  discovered.  There  are  fortytwo  bodies  of  this  class; 
they  are  incapable  of  being  resolved  into  more  simple  parts,  and  are 
therefore  regarded  as  elementary.  Most  of  them  are  remarkable  for 
their  specific  gravity;  they  are  conductors  of  electricity  and  heat, 
they  are  positive  electrics,  opaque,  possess  a peculiar  lustre,  and  are 
in  general  good  reflectors  of  light. 

794.  The  following  table  contains  their  names,  date  of  discovery, 
specific  gravity  at  60°  F.,  and  symbols. 


Names  of  Metals. 

Dates  of  the  Discovery. 

Specific  Gravity. 

S/mb. 

Gold,  m. 

Silver,  m. 

. 19.267  . . . 

Au. 

• • • • 

. 10.474  . . . 

Ag. 

Iron,  m. 

Copper,  m. 

. 7.788  . . . 

Fe. 

. 8.895  . . . 

Cu. 

Mercury, 

. 13.568  . . . 

Hg- 

Lead,  m. 

. 11.352  . . . 

Pb. 

Tin,  m.  J 

. 7.291  . . . 

Sn. 

Antimony, 

1490  . . 

. 6.702  . . . 

Sb. 

Bismuth, 

1530  . . 

. 9.822  . . . 

Bi. 

Zinc,  m. 

16th  century.  . 

. 6.861  to  7.1 

Zn. 

Arsenic,  i 

► 

1733  ' ■ 

. 5.8843  . . . 

As. 

Cobalt.  j 

. 7.834  . . . 

Co. 

Platinum,  m. 

1741  . . 

. 20.98  . . . 

Pt. 

Nickel,  m. 

1751  . . 

. 8.279  . . , 

Ni; 

Manganese, 

1774  . . 

. 8.013  . . . 

Mn. 

Tungsten, 

1781  . . 

. 17.6  . . . 

W. 

Tellurium, 

Molybdenum, 

1782  . . 

6.115  . . . 

Te. 

1782  . . 

. 8.615  to  8.636  . 

Mo. 

Uranium, 

1789  . . 

. 9.000  . . . 

U. 

Titanium, 

1791  . . 

.5.3  ... 

Ti. 

Chromium, 

1797  . . 

.5+  ... 

Cr. 

Columbium, 

1802  . . 

Ta. 

Palladium,  m.  ) 
Rhodium,  S 

1803  • * 

. 11.3  to  11.8  . . 

Pd. 



R. 

Iridium, 

1803  *.  *. 

. 18.68  .... 

Ir. 

Osmium, 

1803  . . 

Os. 

Cerium, 

1804  . . 

Ce. 

Potassium,  m.  } 

. 0.865  . '.  . 

K. 

Sodium,  m. 

. 0.972  . . . 

Na. 

Barium, 

Strontium, 

1307  ! ! 

Ba. 

Sr. 

Calcium, 

Ca. 

Cadmium,  m. 

1818  . . 

. 8.604  , . . 

Cd. 

Lithium, 

1818  . . 

L. 

Zirconium, 

1824  . . 

Zr. 

Aluminium,  J 

) 

Al. 

Glucinium,  > 

1823  . . 

G. 

Yttrium,  ‘ 

) 

. 

Y. 

Thorium, 

Magnesium 

is29  ! ! 

Th. 

1829  . . 

Mg. 

Vanadium 

Latanium, 

1830  . . 

1839  . . 

V. 

tion  of  ammonia.  It  is  a colourless  powder.  Its  alcoholic  solution  gives  with  potassa 
a fine  purple  colour  which  is  fugitive.  It  contains  from  92  to  93  per  cent,  of  sulphur, 
and  7 or  8 of  nitrogen.  T. 


223 


Fusibility  of  Metals . 


795.  Malleability  and  ductility  are  important  properties  of  metals.* 
Those  metals  which  are  remarkable  for  ductility  are  gold,  silver, 
platinum,  iron,  and  copper. 

796.  The  metals  also  differ  in  tenacity,  in  which  property  iron 
surpasses  all  others.  Their  hardness  also  varies,  some  as  titanium, 
iron,  &c.,  are  very  hard ; others,  as  lead,  are  soft,  and  a few,  as  po- 
tassium, yield  to  the  pressure  of  the  fingers. 

797.  Some  of  the  malleable  and  ductile  metals  have,  also,  a high 
degree  of  elasticity.  This  property  fits  them  for  being  applied  to 
the  mechanical  purpose  of  springs.  Steel  and  iron  are  in  this  re- 
spect, superior  to  all  other  metals.  Upon  the  properties  of  elasticity 
and  hardness,  appears  also  to  depend  that  of  fitness  for  exciting 
sound. 

798.  Many  of  the  metals  have  a distinct  crystalline  structure,  and 
not  only  occur  in  nature  in  distinct  crystals,  but  can  be  obtained  in 
that  state  by  careful  fusion  and  cooling. 

Thus  bismuth,  melted  in  a crucible,  and  suffered  to  cool,  becomes 
covered  with  a crUst,  and  when  this  is  pierced,  and  the  fluid  be- 
neath allowed  to  flow  out,  the  cavity  is  found  studded  with  beautiful- 
ly regular  cubic  crystals. 

799.  Metals,  with  the  exception  of  mercury,  are  solid  at  common 
temperatures ; but  they  may  all  be  liquefied  by  heat.  The  degree 
at  which  they  fuse,  or  their  point  of  fusion , is  very  different  for  dif- 
ferent metals,  as  appears  from  the  following  table. 


Fusible  below  a 
red  heat 


Infusible  below  a 
red  heat. 


Table  of  the  Fusibility  of  different  Metals. 

Fahr. 


Mercury 
Potassium 
Sodium 
Cadmium 
Tin,  . 

Bismuth 
Lead  . 

Tellurium  — rather 
fusible  than  lead. 
Arsenic — undetermined . 
Zinc  .... 
Antimony  a little  below 
a red  heat. 

Silver 


about 


less 


773 


Different  chemists. 
Gay-Lussac  and  Thenard. 
Stromeyer. 

Crichton. 

Klaproth. 

Daniel!. 


Copper 
Gold  . 

Iron,  cast 
Iron,  malleable 
Manganese 

Cbbalt — rather  less  fu- 
sible than  iron. 

Nickel — nearly  the  same  as  cobalt. 
Palladium 


DanielL 


1873 
1996 
2016 
2786  [ _ 

Requiring  the  highest  heat  of  a 
smith’s  forge. 


Molybdenum 
Uranium 
Tungsten 
Chromium 
Titanium 
Cerium 
Osmium 
Iridium  )> 
Rhodium  I 
Platinum  j 
Columbium  j 


> 


Almost  infusible,  and  not 
to  be  procured  in  but- 
tons by  the  heat  of  a 
smith’s  forge. 


Fusible  be- 
fore the  oxy- 
hydrogen 
blow-pipe. 


Infusible  in  the  heat  of  a smith’s  forge,  but 
fusible  before  the  oxy-hydrogen  blow-pipe- 


Sect.  I. 


Tenacity. 


Elasticity. 


Structure. 


Crystalli- 

zation. 


Fusibility 
of  Metals. 


* The  malleable  metals  are  designated  in  the  table  by  the  letter  m.,  to  which  may 
be  added  frozen  mercury. 


224 


Metals . 


Chap.  IV. 
Volatile. 

Action  of 
metals  up- 
on each 
other. 
Alloys. 


Amalgams. 


Characters 
of  alloys. 


Union  with 
other  bo- 
dies. 


Combusti- 

ble. 


Product. 


800.  Some  metals  are  volatilized  by  heat,  others  may  be  exposed 
to  the  intense  heat  of  a wind  furnace  without  being  raised  in  va- 
pour. 

The  metals  may  for  the  most  part  be  combined  with  each  other, 
forming  a very  important  class  of  compounds,  the  metallic  alloys. 

The  word  alloy  is  a general  term  for  all  combinations  of  metals 
with  each  other ; and  the  specific  name  is  derived  from  that  of  the 
metal,  which  prevails  in  the  compound.  Thus  in  the  alloy  of  gold 
with  silver , the  gold  is  to  be  understood  as  being  in  greatest  propor- 
tion ; in  the  alloy  of  silver  with  gold , the  silver  is  the  principal  in- 
gredient.* 

The  compounds  of  mercury  with  other  metals,  at  a very  early  pe- 
riod of  chemistry,  were  called  amalgams,  and  the  term  is  still  retained. 

801.  When  metals  are  alloyed  their  properties  are  more  or  less 
affected. 

1.  We  observe  a change  in  the  ductility,  malleability,  hardness, 
and  colour.  Malleability  and  ductility,  are  usually  impaired,  and 
often  in  a remarkable  degree. 

*2.  The  specific  gravity  of  an  alloy  is  rarely  the  mean  of  its  com- 
ponent parts  ; in  some  cases  an  increase,  in  others  a diminution  of 
density  having  taken  place. 

3.  The  fusibility  of  an  alloy  is  generally  greater  than  that  of  its 
components. 

4.  Alloys  are  generally  more  oxidizable  than  their  constituents, 
taken  singly. 

802.  The  metals,  although  they  readily  unite  with  the  elementary 
substances,  are  little  disposed  to  combine  in  the  metallic  state,  with 
compound  bodies,  such  as  an  oxide  or  an  acid.  Their  union  with 
the  simple  non-raetallic  substances,  such  as  oxygen,  chlorine,  and 
sulphur,  gives  rise  to  new  bodies  in  which  the  metallic  character  is 
wholly  wanting.  In  all  these  combinations  the  tendency  to  unite  in 
definite  proportions  is  conspicuous ; the  chemical  changes  are  regu- 
lated by  the  same  general  laws  already  described,  and  the  same 
nomenclature  is  applicable. 

803.  Metals  are  of  a combustible  nature;  that  is,  they  are  not 
only  susceptible  of  slow  oxidation,  but,  under  favorable  circumstan- 
ces, they  unite  rapidly  with  oxygen,  giving  rise  to  all  the  phenomena 
of  real  combustion.  Zinc  burns  with  a brilliant  flame  when  heated 
to  full  redness  in  the  open  air;  iron  emits  vivid  scintillations  on  be- 
ing inflamed  in  an  atmosphere  of  oxygen  gas;  and  the  least  oxida- 
ble  metals,  such  as  gold  and  platinum,  scintillate  in  a similar  man- 
ner when  heated  by  the  oxy-hydrogen  blow-pipe. 

S04.  The  product  either  of  the  slow  or  rapid  oxidation  of  a met- 
al, when  heated  in  the  air,  has  an  earthy  aspect,  and  was  called  a 


* Various  processes  are  adopted  in  the  formation  of  alloys  depending  upon  the  na- 
ture of  the  metals.  Many  are  prepared  by  simply  fusing  the  two  metals  in  a cov- 
ered crucible  ; but  if  there  be  a considerable  difference  in  the  specific  gravity  of  the 
metals,  the  heavier  will  often  subside,  and  the  lower  part  of  the  bar  or  ingot,  will 
differ  in  composition  from  the  uppeT  ; this  may  be  prevented  by  agitating  the  alloy 
till  it  solidifies. 

When  one  of  the  metals  is  very  volatile,  it  should  generally  be  added  to  the  other 
after  its  fusion  j and  if  both  metals  be  volatile,  they  may  be  sometimes  united  by  dis- 
tilling them  together. 


Action  of  Chlorine. 


225 


calx  by  the  older  chemists,  the  process  of  forming  it  being  expressed  Sect.  1 
by  the  term  calcination.  Another  method  of  oxidizing  metals  is  by 
deflagration  ; that  is,  by  mixing  them  with  nitrate  or  chlorate  of  po- 
tassa,  and  projecting  the  mixture  into  a red-hot  crucible.  Most  met- 
als may  be  oxidized  by  digestion  in  nitric  acid;  and  nitro-hydro- 
chloric  acid  is  an  oxidizing  agent  of  still  greater  power. 

805.  Some  metals  unite  with  oxygen  in  one  proportion  only,  but  Union  with 
most  of  them  have  two  or  three  degrees  of  oxidation.  Metals  differ  ox^e 
remarkably  in  their  relative  forces  of  attraction  for  oxygen.  Potas- 
sium and  sodium,  for  example,  are  oxidized  by  mere  exposure  to  the 

air  ; and  they  decompose  water  at  all  temperatures,  the  instant  they 
come  in  contact  with  it.  Iron  and  copper  may  be  preserved  in  dry 
air  without  change,  nor  can  they  decompose  water  at  common  tem- 
peratures ; but  they  are  both  slowly  oxidized  by  exposure  to  a moist 
atmosphere,  and  combine  rapidly  with  oxygen  when  heated  to  red- 
ness in  the  open  air.  Iron  has  a stronger  affinity  for  oxygen  than 
copper ; for  the  former  decomposes  water  at  a red  heat,  whereas  the 
latter  cannot  produce  that  effect.  Mercury  is  less  inclined  than  cop- 
per to  unite  with  oxygen.  Thus  it  may  be  exposed  without  change 
to  the  influence  of  a moist  atmosphere.  At  a temperature  of  650° 
or  700°  it  is  oxidized  ; but  at  a red  heat  it  is  reduced  to  the  metallic 
state,  while  oxide  of  copper  can  sustain  the  strongest  heat  of  a blast 
furnace  without  losing  its  oxygen.  The  affinity  of  gold  for  oxygen 
is  still  weaker  than  that  of  mercury  ; for  it  will  bear  the  most  in- 
tense heat  of  our  furnaces  without  oxidation. 

806.  Metallic  oxides  may  be  reduced  to  the  metallic  state  by  heat  Reduction 
alone,  by  the  united  agency  of  heat  and  combustible  matter,  as  in  0 0X1  es‘ 
metallurgy  when  metals  are  extracted  from  their  ores  with  the  aid  of 
charcoal,  &c.,  by  galvanism,  and  by  the  action  of  deoxidizing  agents 

on  metallic  solutions,  as  when  one  metal  is  precipitated  by  another. 

To  a solution  of  the  nitrate  of  oxide  of  silver,  add  a small  quantity  of  Exp. 
mercury,  the  silver  will  be  thrown  down  in  a metallic  form,  and  oxide  of  mer- 
cury be  dissolved  in  the  nitric  acid  and  water. 

From  this  solution  the  mercury  may  be  separated  by  placing  in  it  a polished 
rod  of  copper,  and  a solution  of  nitrate  of  oxide  of  copper  will  be  obtained,  from 
which  the  copper  may  be  precipitated  by  a rod  of  iron. 

S07.  Metals,  like  the  simple  non-metallic  bodies,  may  give  rise  to  Acids  from 
oxides  or  acids  by  combining  with  oxygen.  The  former  are  the  metals, 
most  frequent  products.  The  acids  contain  a larger  quantity  of  oxy- 
gen than  the  oxides  of  the  same  metal. 

808.  Many  of  the  metallic  oxides  have  the  property  of  combining  Oxides  and 
with  acids.  In  some  instances  all  the  oxides  of  a metal  are  capable  acids- 

of  forming  salts  with  acids,  as  is  exemplified  by  the  oxides  of  iron  : 
but,  generally,  the  protoxide  is  the  sole  alkaline  or  salifiable  base. 

Most  of  the  metallic  oxides  are  insoluble  in  water-  Oxides  some- 
times unite  with  each  other  and  form  definite  compounds. 

809.  The  metals  combine  with  chlorine,  and  the  compounds  are  Action  of 
termed  chlorides.  In  some  instances  the  application  of  heat  is  re-  chlorine, 
quir'ed  : the  combination  is  in  some  cases  slow  and  in  others  rapid, 
attended  with  the  evolution  of  light.  The  attraction  of  chlo- 
rine for  the  metals  is  superior  to  that  of  oxygen  ; hence  when 
chlorine  is  brought  into  contact  with  their  oxides,  the  oxygen  is  libe- 
rated and  a chloride  of  the  metal  is  obtained,  the  elements  of  which 

29 


226 


Metals. 


Chap.  IV. 


C haracters 
of  chlo- 
rides, 


Decompo- 
sition of, 


Procured. 


Action  of 
iodine, 


Of  bromine, 


Of  fluorine, 


Of  sulphur. 


Action  of 
heat  on  sul- 
phurets. 


are  so  strongly  united,  that  in  some  cases  they  are  not  separated  by 
intense  heat. 

810.  The  metallic  chlorides  are  mostly  solid  at  common  tempera- 
tures, fusible,  and  susceptible  of  crystallization ; several  of  them  are 
volatile  ; most  of  them  are  soluble.  They  are  of  nearly  all  colours. 

811.  The  chlorides  of  the  common  metals  are  decomposed  at  a red 
heat  by  hydrogen  gas,  hydrochloric  acid  being  disengaged  and  the 
metal  set  free.  When  in  solution  they  may  be  recognised  by  yield- 
ing with  nitrate  of  oxide  of  silver  a white  precipitate,  which  is  chlo- 
ride of  silver.  Several  of  them  decompose  water,  giving  rise  to  the 
formation  of  hydrochloric  acid  and  an  oxide  (617),  or  in  some  cases 
to  a hydrochlorate.* 

812.  Metallic  chlorides  are  frequently  procured  by  dissolving  me- 
tallic oxides  in  hydrochloric  acid,  evaporating  to  dryness,  and  apply- 
ing heat  so  long  as  any  water  is  expelled. 

S13.  The  same  metal  often  forms  more  than  one  compound  with 
chlorine,  and  these  compounds  are  designated  as  the  oxides. 

814.  Iodine  has  a strong  attraction  for  metals  ; and  most  of  the 
compounds  which  it  forms  with  them  sustain  a red  heat  in  close  ves- 
sels without  decomposition.  But  in  the  degree  of  its  affinity  for  me- 
tallic substances  it  is  inferior  to  chlorine  and  oxygen.  The  metallic 
iodides  are  generated  under  circumstances  analogous  to  those  men- 
tioned  for  procuring  the  chlorides. 

The  action  of  iodine  on  metallic  oxides,  when  dissolved  or  sus- 
pended in  water,  is  precisely  analogous  to  that  of  chlorine.  On 
adding  iodine  to  a solution  of  the  pure  alkalies  or  alkaline  earths, 
an  iodide  and  iodate  are  generated. 

815.  Bromine,  in  its  affinity  for  metallic  substances,  is  intermedi- 
ate between  chlorine  and  iodine  ; for  while  chlorine  disengages 
bromine  from  its  combination  with  metals,  metallic  iodides  are  de- 
composed by  bromine.  The  same  phenomena  attend  the  union  of 
bromine  with  metals,  as  accompany  the  formation  of  metallic  chlo- 
rides. 

The  nature  of  the  action  of  fluorine  upon  the  metals  is  im- 
perfectly known  ; it  exerts  an  extremely  powerful  affinity  for  them, 
which  is  the  great  obstacle  to  obtaining  it  in  an  insulated  form. 

816.  Sulphur  has  a strong  tendency  to  unite  with  metals.  The 
metallic  sulpkurets  are  in  some  cases  formed  by  heating  the  metal 
with  sulphur  ; in  others,  by  decomposing  the  sulphates  ; and  in  oth- 
ers, by  the  action  of  hydrosulphuric  acid.  The  sulphurets  are  in 
general  brittle;  some  have  a metallic,  lustre;  others  are  without  lus- 
tre. Some  are  soluble,  others  insoluble  in  water. 

817.  Most  of  the  protosulphurets  support  an  intense  heat  without 
decomposition ; but,  in  general,  those  which  contain  more  than  one 
equivalent  of  sulphur,  lose  part  of  it  when  strongly  heated.  They 
are  all  decomposed  without  exception  by  exposure  to  the  combined 
agency  of  air  or  oxygen  gas  and  heat;  and  the  products  depend  en- 
tirely on  the  degree  of  heat  and  the  nature  of  the  metal.  The  action 


* A difference  of  opinion  exists  among  chemists  as  to  the  action  of  the  chlorides  upon 
water,  some  supposing  them  to  become  hydrochlorates  when  dissolved,  others  main- 
tain that  some  metallic  chlorides  dissolve  as  such.  The  latter  opinion  has  been  adopt- 
ed by  Turner  from  considerations  for  which  see  his  Elements , 272.  See  also  Brande, 
1 . 370. 


Union  of  Metals. 


227 


of  heat  and  air  in  decomposing  metallic  sulphurets  is  the  basis  of  Sect- *• 
several  metallurgic  processes.  The  metallic  bases  of  the  alkalies 
and  alkaline  earths  agree  with  the  common  metals  in  their  disposi- 
tion to  unite  with  sulphur. 

818.  If  a sulphate  be  decomposed  by  hydrogen  or  charcoal,  or  Decompose 
sulphur  ignited  with  an  alkali  or  alkaline  earth,  a metallic  sulphuret 

is  always  the  product.  Direct  combination  between  sulphur  and  a 
metallic  oxide  is  a very  rare  occurrence,  nor  has  the  existence  of 
such  a compound  been  clearly  established.^ 

819.  The  metallic  seleniurets  have  a resemblance  in  their  chemi-  Seieniurets, 
cal  relations  to  the  sulphurets.  They  may  be  prepared  either  by 
bringing  selenium  in  contact  with  the  metals  at  a high  temperature, 

or  by  the  action  of  hydroselenic  acid  on  metallic  solutions.! 

820.  Phosphorus  combines  with  the  greater  number  of  the  metals,  Action  of 
forming  a series  of  metallic  phosphurets.  There  are  three  methods  *;lls  p 
of  forming  them  ; either  by  heating  a mixture  of  phosphorus  and  the 
metal,  or  projecting  phosphorus  upon  the  metal  previously  heated  to 
redness;  or  by  heating  a mixture  of  the  metal  or  its  oxide,  with 
phosphoric  acid  and  charcoal,  or  by  passing  phosphuretted  hydrogen 

over  the  heated  metallic  oxide.  These  phosphurets  have  a metallic 
lustre  ; if  they  contain  a difficultly  fusible  metal  they  are  more  fusi- 
ble than  the  metal  they  contain  ; if  an  easily  fusible  metal,  less  so.t 

821.  When  phosphorus  is  introduced  into  the  solutions  of  those  ^metajlic 

metals  which  have  but  a feeble  attraction  for  oxygen,  it  reduces  0 u 1 * 

them  to  the  metallic  state.  Thus  gold,  silver,  and  platinum  are 
thrown  down  by  immersing  a stick  of  phosphorus  into  their  respec- 
tive solutions. 

822.  Carbon  unites  to  very  few  of  the  metals,  and  of  the  metallic  Action  of 
carburets,  one  only  is  of  importance,  namely,  carburet  of  iron,  or  carbon, 
steel. 

823.  Hydrogen  forms  compounds  with  but  a few  of  the  metals,  Ofhydro- 

which  are  termed  hydrogurets  or  hydrurets,  gen' 

824.  The  metals  may,  for  the  most  part,  be  combined  with  each  Action  of 
other,  forming  a very  important  class  of  compounds,  the  metallic  al-  metals  on 
loys.  Various  processes  are  adopted  in  the  formation  of  alloys  de-  ^a<j  0 er’ 
pending  upon  the  nature  of  the  metals.  Many  are  prepared  by  oys’ 
simply  fusing  the  two  metals  in  a covered  crucible ; but  if  there  be  a 
considerable  difference  in  their  specific  gravity,  the  heavier  will  sub- 
side, and  the  lower  part  of  the  bar  or  ingot  will  differ  in  composition 

from  the  upper  ; this  may  be  to  a great  extent  prevented  by  agitating 
the  alloy  till  it  solidifies. 

825.  Where  one  of  the  metals  is  very  volatile,  it  should  be  added  Of  volatile 
to  the  other  after  its  fusion  ; and  if  both  metals  be  volatile,  they  may  metals, 
be  sometimes  united  by  distilling  them  together. 

826.  Metals  appear  to  unite  with  one  another  in  every  proportion,  Union  in 
thus  there  is  no  limit  to  the  number  of  alloys  of  gold  and  copper.  It  definite 
is  certain,  however,  that  metals  have  a tendency  to  combine  in  defi-  ^ons^ 

* See  Turner,  p.  270. 

t For  the  different  opinions  in  regard  to  these  compounds  see  Ibid,  p.  272. 

t Phosphorus  is  said  to  unite  with  metallic  oxides,  as  when  phosphuret  of  lime  is 
said  to  be  formed  by  passing  the  vapour  of  phosphorus  over  lime  at  a low  red  heat ; 
hut  it  is  probable  that  part  of  the  metallic  oxide  is  decomposed,  and  that  phosphuret 
of  calcium  and  phosphate  of  lime  are  formed.  T. 


228 


Metals. 


Chap.  IV. 

Characters 
of  allays. 


Oxidation 
of  alloys, 


Action  of 
acids. 


Classifica- 
tion of  met- 
als. 


1st  order, 


2d, 


3d. 


nite  proportions ; for  several  atomic  compounds  of  this  kind  occur 
native.* 

827.  When  metals  are  alloyed  they  undergo  great  change  of  pro- 
perties, their  malleability  and  ductility  are  usually  impaired,  and 
the  colours  changed.  The  hardness  is  in  general  increased,  and  the 
elasticity  and  sonorousness  frequently  improved.  The  specific  gra- 
vity of  an  alloy  is  rarely  the  mean  of  its  component  parts,  sometimes 
greater  and  sometimes  less.T  The  fusibility  of  an  alloy  is  generally 
greater  than  that  of  its  components.  Thus  platinum,  when  alloyed  with 
arsenic  is  very  fusible,  and  an  alloy  of  8 parts  of  bismuth,  5 of  lead, 
and  3 of  tin  liquefies  at  212°, 

828.  Alloys  are  generally  more  oxidizable  than  their  constituents, 
taken  singly ; a property  which  is,  perhaps,  partly  referable  to  the 
formation  of  an  electrical  combination.  Thus  the  oxidability  of  zinc 
is  increased  by  the  presence  of  small  quantities  of  iron. 

829.  The  action  of  acids  upon  alloys  may  generally  be  anticipated 
by  a knowledge  of  their  effects  upon  the  constituent  metals;  but  if  a 
soluble  metal  be  alloyed  with  an  insoluble  one,  the  former  is  often 
protected  by  the  latter  from  the  action  of  the  acid.  Thus,  silver,  al- 
loyed with  a large  quantity  of  gold,  resists  the  action  of  nitric  acid 
in  consequence  of  the  insolubility  of  the  latter  metal  in  that  acid ; 
and  in  order  to  render  it  soluble,  it  should  form  about  one  fourth 
part  of  the  alloy,  B.  l.  382. 

830.  To  those  alloys  of  which  mercury  is  a constituent  the  term 
amalgam  is  applied. 

831.  The  metals  may  be  divided  into  two  classes,  viz  : 1,  those 
which  by  oxidation  yield  alkalies  or  earths,  and,  2,  those  the  oxides 
of  which  are  "neither  alkalies  nor  earths.  These  classes  maybe 
subdivided  as  follows  : 

1st.  Metals  that  decompose  cold  water  at  the  moment  of  contact, 
combining  with  its  oxygen  and  liberating  hydrogen.  The  resulting 
oxides  are  caustic,  soluble  in  water,  and  possess  alkaline  properties. 
They  are  called  alkalies , and  their  metallic  bases  alkaline  or  alkali - 
genous  metals.  They  are,  Potassium,  Sodium,  Lithium. 

2d.  Metallic  bases  of  the  alkaline  earths.  These,  with  the  excep- 
tion of  magnesium,  decompose  water  at  common  temperatures.  They 
are,  Barium,  Strontium,  Calcium,  Magnesium. 

3d.  Metallic  bases  of  the  pure  earths.  Aluminium,  Yttrium,  Zir- 
conium, Glucinium,  Thorium. 

The  second  class  includes  the  greater  number  of  the  metals. 
They  unite  with  oxygen,  generally  in  more  than  one  proportion. 
Their  protoxides  have  an  earthy  appearance,  but  with  few  excep- 
tions are  coloured,  and  are  insoluble  in  water.  Most  of  them  act  as 
salifiable  bases  in  uniting  with  acids,  and  forming  salts  ; but  in  this 
respect  they  are  much  inferior  to  the  alkalies  and  alkaline  earths,  by 
which  they  may  be  separated  from  their  combinations.  Several  of 
these  metals  are  capable  of  forming  with  oxygen,  compounds,  which 
possess  the  characters  of  acids.  They  may  be  arranged  as  follows  : 


* This  view  is  supported  by  late  experiments  of  Rudberg,  Ann.  de  Cfi.  et  de  Phys. 
xlviii.  363.  T.  398. 

t For  a table  exhibiting  this  see  Thenard  TraiU  de  Chim.  1 . 394. 


Potassium . 


229 


1.  Metals  which  decompose  water  at  a red  heat.  They  are  seven  Sect-  n 

in  number;  namely,  Subdivi- 

Manganese,  Cadmium,  Cobalt, 

Iron,  Tin,  Nickel, 

Zinc. 

2.  Metals  which  do  not  decompose  water  at  any  temperature,  and 
the  oxides  of  which  are  not  reduced  to  the  metallic  state  by  the  sole 
action  of  heat.  Of  these  there  are  fourteen  in  number;  namely, 


Arsenic, 

Chromium, 

Vanadium, 

Molybdenum, 

Tungsten, 

3,  Metals,  the  oxides  of 
a red  heat.  These  are 


Columbium, 

Antimony, 

Uranium, 

Cerium, 

Bismuth, 


Titanium, 

Tellurium, 

Copper, 

Lead. 


which  are  reduced  to  the  metallic  state  by 


Mercury, 

Silver, 

Gold, 


Platinum,  Osmium, 

Palladium,  Iridium. 

Rhodium,  T. 


Section  II.  Metallic  Bases  of  the  Alkalies. 

832.  Potassium , K.  eq.  39.15,  was  discovered  in  1807  by  Davy.^  Potassium. 
He  obtained  it  by  submitting  caustic  potassa,  or  potash,  to  the  action 

of  Voltaic  electricity  : the  metal  was  slowly  evolved  at  the  negative 
pole. 

From  the  facts  which  have  become’known  respecting  the  powers  Its  exist. 
of  electrical  decomposition,  it  appeared  to  be  a natural  inference,  ence  how 
that  the  same  powers  applied  in  a state  of  the  highest  intensity,  inferred, 
might  disunite  the  elements  of  some  bodies,  which  had  resisted  all 
other  instruments  of  analysis. 

833.  In  his  first  experiments,  Davy  failed  to  effect  the  decomposi-  pavy,s  ex_ 
tion  of  potassa,  owing  to  his  employing  the  alkali  in  a state  of  aque-  petiments. 
ous  solution,  and  to  the  consequent  expenditure  of  the  electrical 
energy  in  the  mere  decomposition  of  water. 

834.  The  chief  difficulty  in  subjecting  potassa  to  electrical  action  Metjlof]of 
is,  that,  in  a perfectly  dry  state,  it  is  a complete  non-conductor  of  obtaining 
electricity.  When  rendered,  however,  in  the  least  degree  moist  by  potassium 
breathing  on  it,  it  readily  undergoes  fusion  and  decomposition,  by  byelectnci 
the  application  of  strong  electrical  powers. 

For  this  purpose,  a piece  of  potassa,  weighing  from  60  to  70  grains,  may  be 
placed  on  a small  insulated  plate  of  platinum,  and  may  be  connected,  in  the  way 
already  described,  with  the  opposite  end  of  a battery,  containing  not  less  than 
100  pairs  of  six  inch  plates.  On  establishing  the  connexion,  the  potassa  will  fuse 
at  both  places,  where  it  is  in  contact  with  the  platinum.  A violent  effervescence 
will  be  seen  at  the  upper  surface,  arising  from  the  escape  of  oxygen  gas.  At 
the  lower  or  negative  surface,  no  gas  will  be  liberated  ; but  small  bubbles  will 
appear,  having  a high  metallic  lustre,  and  being  precisely  similar  in  visible  cha- 
racters to  quicksilver. 

Some  of  these  globules  burn  with  art  explosion  and  bright  flame  ; 
while  others  are  merely  tarnished,  and  are  protected  from  further 
change  by  a white  film,  which  forms  on  their  surface. 

This  production  of  metallic  globules  is  entirely  independent  of  the 


* Phil . Trans.  1808. 


230 


Mttals — Potassium. 


Chap.  IV. 

How  pre- 
served. 


Reasons  for 
considering 
it  a metal,  . 


Other  pro- 
cesses for 
obtaining 
potassium. 


Curaudau’s. 


Wohler’s. 


Properties. 


action  of  the  atmosphere  ; for  Davy  found,  that  they  may  be  pro- 
duced in  vacuo. 

835.  To  preserve  this  new  substance,  it  is  necessary  to  immerse 
it  immediately  in  a fluid  which  does  not  afford  oxygen.  If  exposed 
to  the  atmosphere  it  is  rapidly  converted  back  again  into  the  state  of 
pure  potassa. 

836.  Nothing  could  be  more  satisfactory  than  the  evidence  fur- 
nished by  Davy’s  experiments,  of  the  nature  of  one  of  the  fixed  alka- 
lies. We  have  the  evidence,  both  of  analysis  and  synthesis,  that 
potassa  is  a compound  of  oxygen  with  a peculiar  inflammable  basis. 

837.  In  assigning  to  this  newly  discovered  substance  a fit  place 
among  the  objects  of  chemistry,  Davy  was  induced  to  class  it  among 
the  metals,  because  it  agrees  with  them  in  opacity,  lustre,  malleabi- 
lity, conducting  powers  as  to  heat  and  electricity,  and  in  its  qualities 
of  chemical  combination. 

838.  In  giving  names  to  the  alkaline  bases,  that  termination  was 
adopted  which,  by  common  consent,  has  been  applied  to  other  newly 
discovered  metals.  The  base  of  potassa  was  called  potassium,  and 
the  base  of  soda  sodium  ; and  these  names  have  met  with  universal 
acceptation. 

839.  It  is  not,  however,  by  electrical  means  only  that  the  decom- 
position of  potassa  has  been  accomplished.  Soon  after  Davy’s  dis- 
coveries were  known  at  Paris,  Gay-Lussac  and  Thenard  succeeded  in 
their  attempts  to  decompose  both  the  fixed  alkalies,  without  the  aid 
of  a Voltaic  apparatus,  merely  by  the  intervention  of  chemical  affini- 
ties. Their  process,  though  it  affords  the  alkaline  bases  of  less  pu- 
rity, yields  them  in  much  larger  quantity,  than  the  electrical  analysis. 
It  consists  in  bringing  the  alkalies  into  contact  with  intensely  heated 
iron,  which,  at  this  temperature,  attracts  oxygen  more  strongly  than 
the  alkaline  base  retains  it. 

Potassium  may  also  be  prepared,  as  first  noticed  by  Curaudau,  by 
mixing  dry  carbonate  of  potassa  with  half  its  weight  of  powdered 
charcoal,  and  exposing  the  mixture,  contained  in  a gun-barrel  or 
spheroidal  iron  bottle,  to  a strong  heat.  An  improvement  on  both 
processes  has  been  made  by  Brunner,  who  decomposes  potassa  by 
means  of  iron  and  charcoal.  From  eight  ounces  of  fused  carbonate 
of  potassa,  six  ounces  of  iron  filings,  and  two  ounces  of  charcoal 
mixed  intimately  and  heated  in  an  iron  bottle,  he  obtained  140  grains 
of  potassium.* 

A modification  of  this  process  has  been  described  by  Wohler,  who 
effects  the  decomposition  of  the  potassa  solely  by  means  of  charcoal. 
The  material  employed  for  the  purpose  is  carbonate  of  potassa,  pre- 
pared by  heating  cream  of  tartar  to  redness  in  a covered  crucible. f 

840.  Potassium  is  a white  metal  of  great  lustre.  It  exists  in 
small  globules,  which  possess  the  opacity,  and  general  appearance  of 
mercury  ; so  that  when  a globule  of  mercury  is  placed  near  one  of 
potassium  the  eye  can  discover  no  difference  between  them.  It  in- 


* Quart.  Jour.  xv.  379.  See  also  Henry’s  Chcm.  vol.  i.  Hare  in  Avxer.  Jour.  xxiv. 
312,  and  Gale’s  method  ibid,  xxi.  60.  Very  full  practical  directions  are  given  in  Reid’s 
Ele.  of  Prac.  Chern.  p.  221. 

t PoggendorfTs  Annalen , iv.  23,  and  Brande’s  Jour.  xxii. 


231 


Protoxide  of  Potassium — Potassa. 

stantly  tarnishes  by  exposure  to  air.  It  is  ductile,  and  of  the  con-  ^ct.  u. 
sistency  of  soft  wax. 

Its  specific  gravity  is  0.865.  At  150°  it  enters  into  perfect  fusion ; 
and  at  a bright  red  heat  rises  in  vapour.  At  32°  it  is  a hard  and 
brittle  solid.  If  heated  in  air  it  burns  with  a brilliant  white  flame. 

It  is  an  excellent  conductor  of  electricity  and  of  heat. 

S41.  Its  most  prominent  chemical  property  is  its  great  affinity  for  Prominent 
oxygen.  It  oxidizes  rapidly  in  the  air,  or  by  contact  with  fluids  cbaracter* 
which  contain  oxygen.  On  this  account  it  must  be  preserved  either 
in  glass  tubes  hermetically  sealed,  or  under  the  surface  of  liquids, 
of  which  oxygen. is  notan  element,  such  as  naptha,  or  what  is  better 
the  essential  oil  of  copaiva. 

842.  If  heated  in  the  open  air,  it  takes  fire  and  burns  with  a pur-  Decompo- 
ple  flame  and  great  evolution  of  heat.  It  decomposes  water  on  the  ses  water* 
instant  of  touching  it,  and  so  much  heat  is  disengaged,  that  the  po- 
tassium is  inflamed,  and  burns  vividly  while  swimming  upon  its 
surface.  The  hydrogen  unites  with  a little  potassium  at  the  moment 

of  separation  ; and  this  compound  takes  fire  as  it  escapes,  and  thus 
augments  the  brilliancy  of  the  combustion.  When  potassium  is 
plunged  under  water,  violent  reaction  ensues,  but  without  light,  and 
pure  hydrogen  gas  is  evolved. 

Take  a small  piece  of  potassium,  remove  the  naptha  adhering  to  it  by  blotting  Exp. 
paper,  and  drop  it  into  water ; after  the  combustion,  add  to  the  water  infusion  of 
purple  cabbage,  which  will  become  green. 

Place  another  piece  upon  a lump  of  ice,  the  same  action  takes  place.  Exp. 

Gunpowder  may  be  ignited  by  placing  upon  it  a piece  of  potassium  and  touch-  Exp. 
ing  the  metal  with  a drop  of  water  on  a rod,  or  with  ice. 

Introduce  a piece  of  the  metal,  wrapped  up  in  paper,  quickly  into  a test  tube  Exp. 
inverted  in  and  full  of  water.  It  will  rise  to  the  top,  and  when  the  water  reaches 
it  through  the  paper,  it  will  be  decomposed  and  hydrogen  be  found  in  the  upper 
part  of  the  tube,  which  may  be  inflamed  in  the  usual  way. 

A small  piece  may  be  dropped  into  a little  sulphuric  acid,  contained  in  ajar  3 Exp. 
or  4 inches  in  diameter  and  about  10  or  12  inches  deep  : potassa  is  formed  and 
heat  and  light  are  at  the  same  time  evolved.  Care  must  be  taken  that  none  of 
the  acid  is  thrown  into  the  eyes. 

Put  4 grains  of  iodine  into  a test  tube  about  4 or  5 inches  long,  throw  a grain  Exp. 
of  potassium  upon  it,  and  hold  the  sealed  end  of  the  tube  for  a second  or  two  in 
the  flame  of  a spirit  lamp.  The  iodine  and  potassium  will  rapidly  combine  with 
a brilliant  light.  The  hand  should  be  protected  with  a glove  as  the  tube  is  usu- 
ally broken. 

A similar  experiment  may  be  made  with  half  a grain  of  sulphur  and  a grain  of  Exp. 
potassium. 

843.  The  combining  weight  or  equivalent  of  potassium  is  easily  Equivalent, 
deduced  from  the  composition  of  potassa  and  chloride  of  potassium, 

which  are  admitted  to  consist  of  single  equivalents  of  their  elements. 

Berzelius  analyzed  chloride  of  potassium  by  means  of  nitrate  of  oxide 
of  silver,  and  inferred  that  39.15  is  the  equivalent  of  potassium. 

Compounds  of  Potassium. 

844.  Protoxide  of  Potassium — Potash,  or  Potassa , K-f-O,  K or  Protoxide 
KO,  39.15  1 eq.  potas.  -f*  8 1 eq.  oxy.  = 47.15  equiv.,  is  formed  or  potassa. 
when  potassium  is  put  into  water,  or  exposed  to  dry  air  or  oxygen 

gas  ; formed  in  the  latter  way  it  is  anhydrous.  It  is  a white  caus- 
tic solid,  fusing  at  a temperature  above  redness,  and  not  decomposed 
by  the  heat  of  a wind  furnace.  It  has  a great  affinity  for  water. 


232 


Metals — Potassium. 


Chap.  IV. 

Protohy- 
drate, <vc. 


Use. 


Purified. 


Pure  pot- 
assa. 


Characters. 


Potassa 
how  dis- 
tinguished. 


IVeparation  of 
pure  potassa. 


845.  There  are  three  compounds,  containing  each  1 eq.  of  po- 
tassa with  1.3  and  5 eq.  of  water  respectively.  The  Protohydrate 
is  caustic  potash , potassa  fusa  of  the  London  pharmacopoeia.  It  was 
formerly  called  lapis  causticus.  It  is  solid  at  common  temperatures, 
is  highly  deliquescent,  and  requires  about  half  its  weight  of  water  for 
solution.  It  is  soluble  in  alcohol.  Its  sp.  gr.  is  1.706.  In  surgery 
it  is  used  as  a caustic,  and  is  prepared  by  evaporating  the  aqueous 
solution  and  casting  it  in  moulds.  In  this  state  it  is  impure.  It  is 
purified  by  solution  in  alcohol,  and  evaporation  to  the  consistence  of 
oil  in  a vessel  of  pure  silver,  which  should  be  done  expeditiously  to 
avoid  the  absorption  of  carbonic  acid.* 

846.  Potassa  thus  purified  is  white,  very  acrid  and  corrosive,  and 
at  a bright  red  heat  evaporates  in  the  form  of  white  acrid  smoke.  It 
quickly  absorbs  moisture  and  carbonic  acid  from  the  air.  It  is  highly 
alkaline,  and  being  exclusively  procured  from  vegetables  was  for- 
merly called  vegetable  alkali.  When  touched  with  moist  fingers  it 
has  a soapy  feel,  in  consequence  of  its  action  upon  the  cuticle.  In 
the  fused  state  it  produces  heat  when  dissolved  in  water  ; but  in  its 
crystallized  state  it  excites  considerable  cold,  especially  when  mixed 
with  snow.  At  a natural  temperature  of  30°,  Lowitz  found  that 
equal  weights  of  crystallized  potassa  and  snow  depressed  the  ther- 
mometer to  45°. 

847.  Potassa  may  be  distinguished  from  all  other  substances  by 
the  following  characters.  If  tartaric  acid  be  added  in  excess  to  a 
salt  of  potassa  dissolved  in  water,  and  the  solution  be  stirred  with  a 
glass  rod,  a white  precipitate,  the  bitartrate  of  potassa,  soon  appears, 
which  forms  peculiar  white  streaks  upon  the  glass  by  the  pressure  of 
the  rod  in  stirring.  A solution  of  chloride  of  platinum  causes  a yel- 
low precipitate,  the  double  chloride  of  platinum  and  potassium.  Al- 
coholic solution  of  carbazotic  acid  throws  down  potassa  in  yellowish 
crystals  of  carbazotate  of  potassa,  which  is  very  sparingly  soluble. 


* To  prepare  pure  potash,  carbonate  of  potash  may  be  dissolved  by  rubbing  it  with 
four  limes  its  weight  of  water  in  an  earthen  mortar;  the  solution  is  then  decanted,  and 
mixed  with  a quantity  of  newly  slaked  lime  equal  in  weight  to  the  carbonate  employed, 
boiling  it  for  a few  minutes,  and  then  filtering.  To  avoid  absorption  of  carbonic  acid 
from  the  air,  the  best  method  is  to  use  a funnel,  with  a narrow  mouth,  which  may  ea- 
sily be  closed  by  a cork  or  stopper,  and  putting  a small  tube  through  the  throat  of  the 
funnel,  placing  pieces  of  quartz  or  broken  glass  round  it,  and  covering  it  with  linen,  so 
that  while  the  solution  of  potassa  is  dropping  into  the  bottle  below,  air  passes  through 
the  tube  at  the  same  time  from  the  lower  to  the  upper  vessel  and  supplies  its  place. 
This  method,  proposed  by  Duncan  is  an  excellent  substitute  for  a more  complicated 
apparatus.  When  a common  funnel  is  employed,  it  should  be  covered  with  a plate  or 
tin  tray,  and  a towel  thrown  over  the  whole.  (Reid.)  For  an  apparatus  devised  by  Do- 
novan for  this  purpose,  see  Turner’s  Elements, p.  279.  As  part  of  the  solution  of  po- 
tassa adheres  to  the  lime,  a small  quantity  of  water  is  to  be  poured  on  the  top  of  what 
remains  in  the  funnel  after  it  has  ceased  to  drop;  the  water  presses  upon  the  liquid  it 
still  contains,  and  causes  it  to  pass  slowly  into  the  receiver  below.  This  is  continued  till 
a quantity  of  liquid  is  obtained  equal  to  5 or  6 times  the  weight  of  the  salt  employed. 
It  must  be  kept  in  glass  bottles  with  good  stoppers. 

If  the  liquid  contains  little  carbonic  acid,  it  will  give  a very  slight  precipitate  with 
lime  water,  and  scarcely  any  effervescence  will  be  seen  with  sulphuric  acid.  The 
potash  may  be  separated  from  the  water  by  adding  to  the  solution  an  equal  quantity  of 
alcohol,  in  a large  well  stopped  bottle,  and  shaking  them  together.  After  repose  the 
alcohol  floats  above,  holding  the  potash  in  solution  and  is  to  be  poured  off.  From 
the  alcoholic  solution  the  potash  is  obtained  by  rapid  evaporation  in  a retort  when  it  is 
desirable  to  save  the  alcohol,  or  in  an  evaporating  dish  when  not  so.  Or  the  fused 
potash  may  he  dissolved  at  once  in  alcohol  and  the  solution,  after  standing,  be  decant- 
ed, evaporated,  and  fused  as  before. 


233 


Sulphurets  of  Potassium. 

This  is  the  most  delicate  test  in  a solution  of  pure  potassa ; but  Sect.  11. 
when  the  alkali  is  combined  with  a strong  acid,  the  chloride  of  plat-  Test  of. 
inum  is  preferable.^ 

848.  Chloride  of  Potassium , K-j-Cl  or  KC1,  39.15  1 eq.  potas.  -f- 
35.42  1 eq.  chlor.  = 74.57  equiv.,  is  formed  when  potassium  burns 
in  chlorine  gas,  and  when  it  is  heated  in  hydrochloric  acid  gas.  It 
is  also  the  residuum  after  the  decomposition  of  chlorate  of  potassa 
by  heat.  It  is  formed  when  potassa  is  dissolved  in  a solution  of 
hydrochloric  acid.  It  was  formerly  called  salt  of  Sylvius  and  regen- 
erated sea  salt.  It  crystallizes  in  cubes,  and  has  a saline  and  bitter 
taste. 

849.  Iodide  of  Potassium , K— |— I or  KI,  39.15  1 eq.  potas.  -f-  126.3 
1 eq.  iod.  = 165.45  equiv.,  is  formed  when  potassium  is  heated  in 
contact  with  iodine. 

It  may  be  prepared  by  adding  iodine  to  a hot  solution  of  pure  potassa  until  the  Process, 
alkali  is  neutralized,  evaporating  to  drynesS  and  exposing  the  dry  mass  in  a plat- 
inum crucible  to  a gentle  red  heat.  The  fused  mass  is  dissolved  out  by  water 
and  crystallized. 

850.  It  fuses  and  rises  in  vapour  at  a heat  below  redness,  is  solu-  ProPerties* 
ble  in  two  thirds  its  weight  of  water  at  60°.  Its  solution  in  alcohol 

yields  colourless  cubic  crystals. 

It  should  be  purchased  in  crystals,  which  ought  not  to  deliquesce 
in  a moderately  dry  air,  and  in  powder  should  be  completely  soluble 
in  the  strongest  alcohol. t 

851.  Hydrogen  and  Potassium  unite  in  two  proportions,  forming  ^dro0gt|n 
in  one  case  a solid  and  in  the  other  a gaseous  compound.  The  lat-  sium?°taS" 
ter  is  produced  when  hydrate  of  potassa  is  decomposed  by  iron  at  a 

white  heat.  It  inflames  spontaneously  in  air  or  oxygen  gas. 

The  solid  hydruret  of  potassium  was  made  by  Gay-Lussac  and 
Thenard,  by  heating  potassium  in  hydrogen  gas.  It  does  not  in- 
flame spontaneously  in  oxygen  gas.  $ 

852.  Sulphurets  of  Potassium. — Potassium  unites  readily  with  Sulphurets, 
sulphur  by  the  aid  of  gentle  heat,  emitting  so  much  heat  that  the 

mass  becomes  incandescent.  The  nature  of  the  product  depends 

* Turner. 

+ Teroxide  of  Potassium , K+30,  K or  KO3  39.15  I eq.  potas.  -f-  24  3 eq.  oxy.  = Teroxide. 
63.15  equiv.,  is  formed  when  potassium  is  burnt  in  the  open  air  or  in  oxygen  gas. 

It  is  the  residue  of  the  decomposition  of  nitre  by  heat  in  metallic  vessels  ; provided 
the  temperature  be  kept  up  sufficiently  long.  When  water  is  added  to  it  oxygen 
escapes  with  effervescence,  and  it  passes  to  the  state  of  potassa  which  is  dissolved.* 

Bromide  of  Potassium,  K+Br  or  KBr.,  39.15  1 eq.  potas.  + 78.4  1 eq.  oxy.  = Bromide. 
117.55  equiv.  This  compound  is  formed  by  processes  similar  to  that  for  preparing 
the  iodide,  and  is  analogous  to  it  in  most  of  its  properties-  It  is  but  slightly 
soluble  in  alcohol. 

Fluoride  of  Potassium,  K+F,  or  KF.  39.15  1 eq.  potas.  + 18.68  l eq.  fluor.  Fluoride. 

= 57.83  equiv.,  is  best  formed  by  nearly  saturating  hydrofluoric  acid  with  carbonate 
of  potassa,  evaporating  to  dryness  in  platinum,  and  igniting  to  expel  any  excess  of 
acid.  It  may  be  obtained  in  cubes  or  rectangular  four-sided  prisms,  which  deliquesce 
rapidly.  The  solution  acts  on  glass  in  which  it  is  kept  or  evaporated. 

t Carburet  of  Potassium  has  not  been  obtained  in  a pure  state  ; but  it  is  thought 
to  form  part  of  the  residue  in  the  preparation  of  potassium  from  charcoal,  (page  230). 

* Bridges  of  Philadelphia,  has  suggested  this  as  a convenient  method  of  obtaining  oxygen 
gas.  See  Turner’s  Elem.  280,  and  J\T.  A.  Med.  and  Surg.  Jour.  v.  241. 

30 


234 


Metals — Sodium . 


Chap.  IV. 


Proto, 


Ter. 


Discovery 
of  sodium. 


Properties. 


Pho«phur*ti. 


SeleniOMti. 


on  the  proportions  which  are  employed.  The  protosulphuret  is 
readily  prepared  by  decomposing  sulphate  of  potassa  by  charcoal  or 
hydrogen  gas  at  a red  heat. 

Protosulphuret  of  Potassium , K-f-S  or  KS,  39.15  1 eq.  potas. 
-(-  16.1  1 eq.  sulp.  = 55.25  equiv.,  fuses  below  a red  heat,  and 
acquires  on  cooling  a crystalline  texture.  It  has  a red  colour,  de- 
liquesces on  exposure  to  the  air,  and  is  soluble  in  water  and  alcohol. 
It  takes  fire  when  heated  before  the  blow-pipe,  and  quickly  acquires 
a coating  of  sulphate  of  potassa,  which  stops  the  combustion;  but 
when  mixed  in  fine  division  with  charcoal,  it  kindles  spontaneously, 
forming  a good  pyrophorus.* 

Tersulphuret  of  Potassium , K+3S  or  KS*,  39.15  1 eq.  potas. 
-)-  48.3  3 eq.  sulp.  = 87.45  equiv.,  is  prepared  pure  by  transmit- 
ting the  vapour  of  bisulphuret  of  carbon  over  carbonate  of  potassa 
at  a red  heat,  as  long  as  carbonic  acid  or  carbonic  oxide  gases  are 
disengaged.  It  is  also  formed  when  carbonate  of  potassa  is  heated 
to  low  redness  with  half  its  weight  of  sulphur,  until  the  mass  ap- 
pears in  tranquil  fusion.!  This  is  known  as  liver  of  sulphur. 

Sodium. 

Symb.  Na  Equiv.  23-3 

853.  Sodium  discovered  by  Davy  in  1S08,  is  obtained  from 
soda  by  an  operation  analogous  to  that  for  procuring  potassium 
from  potassa.  (832.)  It  is  soft,  easily  sectile,  white  and  opaque,  and 
when  examined  under  a thin  film  of  naptha  has  the  lustre  and  gen- 
eral appearance  of  silver. 

854.  It  is  exceedingly  malleable,  and  much  softer  than  any  of  the 
common  metallic  substances.  When  pressed  upon  by  a platinum 
blade  with  a small  force  it  spreads  into  thin  leaves  ; and  a globule 
of  -j^th  ;or  xVth  of  an  inch  in  diameter  is  easily  spread  over  a sur- 
face of  a quarter  of  an  inch.  This  property  is  not  diminished  by 
cooling  it  to  32°  F.  Several  globules,  also,  may,  by  strong  pres- 
sure, be  forced  into  one  ; so  that  the  property  of  welding , which  be- 


* Bisulphuret  of  Potassium , K+2S  or  KS2.  39.15  1 eq.  potas-  -f  32.2  2 eq.  sulp. 
= 71.35  equiv.,  is  formed  by  exposing  a saturated  solution  in  alcohol  of  hydro- 
sulphate  of  sulphuret  of  potassium  (KS+HS),  until  a pellicle  begins  to  form  upon 
its  surface,  and  then  evaporating  to  dryness  without  further  exposure. 

t Quadrosulphuret  of  Potassium,  K-MS  or  KS4,  39.15  1 eq.  potas.  -f  64.4  4 eq. 
= 103.55  equiv.,  is  prepared  by  transmitting  the  vapour  of  bisulphuret  of  carbon  over 
sulphate  of  potassa  at  a red  heat,  until  carbonic  acid  gas  ceases  to  be  disengaged. 

Quintosulphuret  of  Potassium,  K+5S  or  KS5,  39.15  1 eq.  potas.  + 80-5  5 eq. 
sulp.  = 119.65  equiv.,  is  formed  by  fusing  carbonate  of  potassa  with  its  own  weight 
of  sulphur,  the  residue  containing  sulphate  of  potassa  as  in  preparing  the  tersulphuret. 

These  four  last  sulphurets  are  deliquescent  in  the  air,  have  a sulphurous  odour, 
and  are  soluble  in  water  5 and  those  who  consider  them  to  decompose  water  in  dis- 
solving, suppose  the  formation  of  corresponding  compounds  of  hydrogen  and  sul- 
phur. 

Phosphurets  of  Potassium. — When  potassium  is  heated  in  phosphuretted  hydro- 
gen gas,  it  takes  fire,  phosphuret  of  potassium  is  formed,  and  hydrogen  set  free;  and 
combination  is  also  effected  by  gently  heating  phosphorus  with  potassium.  The 
number  and  proportion  of  these  compounds  have  not  yet  been  determined. 

Seleniurets  of  Potassium. — These  elements  unite  when  fused  together,  sometimes 
with  explosive  violence,  forming  a crystalline  fusible  compound  of  an  iron-gray  col- 
our and  metallic  lustre. 


Oxides  of  Sodium . 


235 


longs  to  platinum  and  iron  at  a high  degree  of  heat  only,  is  pos- — — L 

sessed  by  this  substance  at  common  temperatures. 

It  is  lighter  than  water;  as  near  as  can  be  determined,  its  specific 
gravity  is  as  0.972  to  1. 

855.  It  is  much  less  fusible  than  the  base  of  potassa.  At  120°  Fusibility. 
F.,  it  begins  to  lose  its  cohesion,  and  is  a perfect  fluid  at  200°. 

856.  When  sodium  is  exposed  to  the  atmosphere,  it  immediately  Effect  of 
tarnishes,  and  by  degrees  becomes  covered  with  a white  crust  of  air> 
soda,  which  deliquiates  more  slowly  than  that  formed  on  potassium. 

It  is  not  changed,  however,  by  air  that  has  been  artificially  dried. 

857.  It  combines  with  oxygen,  slowly  and  without  luminous  ap- Of  oxygen, 
pearance,  at  all  common  temperatures.  When  heated  to  its  fusing 

point,  the  combination  becomes  more  rapid  ; but  no  light  is  emitted 
till  it  becomes  nearly  red  hot.  The  flame  which  it  then  produces, 
is  white,  and  it  sends  forth  bright  sparks,  exhibiting  a very  beautiful 
effect.  In  common  air,  it  burns  with  a similar  colour  to  charcoal, 
but  with  much  greater  splendour. 

858.  When  thrown  on  cold  water,  it  swims,  and  is  rapidly  oxi-  Action  on 
dized,  though  in  general,  without  inflaming,  but  with  hot  water  it  water> 
scintillates,  or  even  takes  fire.  If  the  sodium  is  confined  to  one 

spot  and  the  water  rests  on  a non-conducting  substance,  as  charcoal, 
the  heat  rises  high  enough  for  inflammation.^  In  each  case  soda  is 
formed,  and  the  water  acquires  an  alkaline  reaction. 

859.  Its  action  on  alcohol,  ether,  volatile  oil,  and  acids,  is  similar  alcohol 

to  that  of  potassium  ; but  with  nitric  acid  a vivid  inflammation  is  &c.  * 

produced. 

860.  Protoxide  of  Sodium , Na-f-O,  Na  or  Nao,  23.3  1 eq.  sod.  Protoxide, 
+ 8 1 eq.  oxy.  ==  31.3  equiv.,  commonly  called  soda,  and  by  the°rsotla> 
Germans  natron,  is  formed  by  the  oxidation  of  sodium  in  air  and  wa- 
ter, as  potassa  is  from  potassium.  In  its  anhydrous  state  it  is  a gray 

solid,  difficult  of  fusion,  and  very  similar  in  its  characters  to  potassa. 

With  water  it  forms  a solid  hydrate,  easily  fusible  by  heat,  very 
caustic,  soluble  in  water  and  alcohol,  has  powerful  alkaline  proper- 
ties, and  in  all  its  chemical  relations  is  exceedingly  analogous  to  po- 
tassa. It  is  prepared  from  the  solution  of  pure  soda,  in  the  same 
manner  as  the  corresponding  preparation  of  potassa.  The  solid  hy- 
drate is  composed  of  31-3  parts  or  one  equivalent  of  soda,  and  9 
parts  or  1 equivalent  of  water. 

861.  Soda  is  readily  distinguished  from  other  alkaline  bases  by  Distin- 
the  following  characters.  1.  It  yields  with  sulphuric  acid  a salt,  §>uished- 
which  by  its  taste  and  form  is  easily  recognised  as  Glauber’s  salt, 

or  sulphate  of  soda.  2.  All  its  salts  are  soluble  in  water,  and  are 
not  precipitated  by  any  reagent.  3.  On  exposing  its  salts  by  means 
of  platinum  wire  to  the  blow-pipe  flame,  they  communicate  to  it  a 
rich  yellow  colour. 

862.  Sesquioxide  of  Sodium,  2Na-|-30  Na,  or  Na203,  46.6  2 Sesquiox- 

eq.  sod.  — |—  24  3 eq.  oxy.  = 70.6  equiv.,  is  formed  when  sodium  is 
heated  to  redness  in  an  excess  of  oxygen  gas.  It  has  an  orange 
colour,  has  neither  acid  nor  alkaline  properties,  and  is  resolved  by 
water  into  soda  and  oxygen. 


* Ducatel  jq  Ajner.  Jour,  xxy , 90. 


236 


Metals — Sodium . 


Chap.  IV. 
Chloride, 


How  ob» 
tained. 


Common 

salt. 


Solution. 


lodlda. 


Bromide. 


Fluoride, 


863.  Chloride  of  Sodium , Na-j-Cl  or  NaCl,  23.3  1 eq.  sod.  -f- 
35.42  1 eq.  chlor.  = 58.72  equiv.  Sodium,  when  heated  in  chlorine, 
burns  and  produces  a white  compound,  of  a pure  saline  flavour. 
It  may  also  be  formed  by  heating  sodium  strongly  in  hydrochloric 
acid  gas  ; the  hydrogen  of  which  is  liberated,  while  the  chlorine 
combines  with  the  metal. 

864.  Or  it  may  be  formed  by  saturating  carbonate  or  hydrate  of 
soda  with  hydrochloric  acid,  and  evaporating  the  liquid,  which  yields 
chloride  of  sodium  in  a solid  form.  This  chloride,  also,  is  an  abun- 
dant product  of  nature,  being  that  well  known  substance,  common 
salt.  For  purposes  of  experiment,  the  common  salt  maybe  em- 
ployed which  is  to  be  found  in  the  shops.  This  maybe  purified,  by 
adding  to  a solution  of  it  in  water  a solution  of  carbonate  of  soda,  as 
long  as  any  milkiness  ensues  ; filtering  the  solution,  and  evaporating 
it  till  it  crystallizes. 

865.  It  crystallizes  in  solid  regular  cubes,  or,  by  hasty  evapora- 
tion, in  hollow  quadrangular  pyramids,  which,  when  the  salt  is  pure, 
are  but  little  changed  by  exposure  to  the  air.  The  common  salt  of 
the  shops,  however,  being  impure,  acquires  an  increase  of  weight,  in 
consequence  of  the  absorption  of  moisture.  The  various  forms  un- 
der which  it  appears,  of  stoved  salt,  fishery  salt,  bay  salt,  &c.  arise 
from  modifications  in  the  size  and  compactness  of  the  grain,  rather 
than  from  any  essential  difference  of  chemical  composition.  Com- 
mon salt  always  contains  small  quantities  of  sulphate  of  magnesia 
and  lime,  and  chloride  of  magnesium.  These  may  be  precipitated 
as  carbonates  by  boiling  a solution  of  salt  for  a few  minutes  with  a 
slight  excess  of  carbonate  of  soda,  filtering  the  liquid  and  neutraliz- 
ing with  hydrochloric  acid. 

866.  It  requires  for  solution,  twice  and  a half  its  weight  of  water, 
at  60°  F.,  and  hot  water  takes  up  very  little  more.  Hence  its  solu- 
tion crystallizes,  not  like  that  of  nitre,  by  cooling,  but  by  evaporation. 
When  heated  gradually  it  fuses,  and  forms,  when  cold,  a solid  com- 
pact mass.  If  suddenly  heated  as  by  throwing  it  on  red-hot  coals,  it 
decrepitates.  Its  uses  are  well  known. ^ 

867.  Protosulphuret  of  Sodium . Na-f-S,  or  NaS,  23.3  1 eq.  sod. 
-f-16.1  1 eq.  sulph  = 39.4  equiv.  The  protosulphuret  is  obtained 
by  processes  similar  to  those  for  protosulphuret  of  potassium,  to 
which  in  its  taste  and  chemical  relations  it  is  very  similar.! 


* Iodide  of  Sodium.  Na+I,  or  Nal,  23.3  1 eq.  sod.+ 126.3  1 eq.  iod.=149.6  equiv. 
Obtained  pure  by  processes  similar  to  those  for  preparing  iodide  of  potassium ; but 
it  is  contained  in  sea-water,  in  many  salt  springs,  and  in  the  residual  liquor  from  kelp 
(673). 

Bromide  of  Sodium.  Na+Br,  or  NaBr,  23.3  1 eq.  sod. + 78.4  1 eq.  brom.  = 101.7 
equiv.  This  compound  is  very  analogous  to  sea-salt,  and  is  associated  with  it  in  sea- 
water and  most  salt  springs. 

Fluoride  of  Sodium.  Na+F,  or  NaF,  23.3  1 eq.  sod. + 18.68  1 eq.  flu.  =41*98 
equiv.  This  compound  is  formed  by  neutralizing  hydrofluoric  acid  by  soda,  and  by 
igniting  the  double  fluoride  of  sodium  and  silicon,  when  the  fluoride  of  silicon  is  ex- 
pelled. 

* According  to  Gmelin  of  Tubingen,  sulphuret  of  sodium  is  the  colouring  principle 
of  lapis  lazuli !,  to  which  the  colour  of  ultra-marine  is  owing;  and  he  has  succeeded  in 
preparing  artificial  ultra-marine  by  heating  sulphuret  of  sodium  with  a mixture  of  sili- 
cic acid  and  alumina.  Ann.  de  Ch.  et  de  Ph.  xxxvii.  409* 


Barium, 


237 


Lithium . _bect1m1 

Symb.  L.  Equiv.  6.44. 

868.  In  the  year  1818,  in  the  analysis  of  a mineral  called  petalite,  Discovery. 
Arfwedson  discovered  about  three  per  cent,  of  an  alkaline  substance, 

which  was  at  first  supposed  to  be  soda;  but,  the  further  prosecution 
of  his  inquiries  fully  demonstrated  that  it  possessed  peculiar  proper- 
ties. The  minerals  called  spodumene , and  lepidolite , also  afford  the 
same  substance,  to  which  the  term  lithia,  deduced  from  its  lapideous 
original  has  been  applied. 

869.  For  preparing  lithia, 

One  part  of  petalite  or  spodumene,  in  fine  powder,  is  intimately  mixed  with  Method  of 
two  parts  of  fluor  spar,  and  the  mixture  is  heated  with  three  or  four  times  its  obtaining 
weight  of  sulphuric  acid,  as  long  as  any  acid  vapours  are  disengaged.  The  silicic  lithia. 
acid  of  the  mineral  is  attacked  by  hydrofluoric  acid,  and  is  dissipated  in  the  form 
of  fluosilicic  acid  gas,  while  the  alumina  and  lithia  unite  with  sulphuric  acid. 

After  dissolving  these  salts  in  water,  the  solution  is  boiled  with  pure  ammonia  to 
precipitate  the  alumina,  filtered,  evaporated  to  dryness  and  then  heated  to  red- 
ness to  expel  the  sulphate  of  ammonia.  The  residue  is  sulphate  of  lithia.* 

T.  28(5. 

870.  When  lithia  is  submitted  to  the  action  of  the  Voltaic  pile,  it  Action  of 
is  decomposed  with  the  same  phenomena  as  potassa  and  soda ; a galvanism» 
brilliant  white  and  highly  combustible  metallic  substance  is  separat- 
ed, which  is  lithium. 

871.  Lithia.  L-j-O,  L,  or  LO,  6.44  1 eq.  lith.  -|-  8 1 eq.  oxy.  — Distin- 
14.44  equiv.  Lithia  is  allied  to  potassa  and  soda,  but  distinguished  f^^potas- 
by  its  greater  neutralizing  power,  by  its  salts  tinging  the  flame  of  thesa,&c. 
blow-pipe  of  a red  colour.  It  attacks  platinum  when  fused  upon  it, 
leaving  a dull  yellow  trace.  It  is  distinguished  from  baryta,  strontia 

and  lime  by  forming  soluble  salts  with  sulphuric  and  oxalic  acids. t 


Section  III.  Metallic  Bases  of  the  Alkaline  Earths. 

872.  Barium,  Ba.  eq.  68.7,  was  discovered  by  Davy,  in  1808,  by  Barium  5 
means  of  galvanism.  He  placed  a globule  of  mercury  in  a hollow  discovery° 
made  in  a paste  of  carbonate  of  baryta,  on  a platinum  tray  commu- 
nicating with  the  positive  pole  of  a battery  of  100  double  plates, 

while  the  negative  wire  was  in  contact  with  the  mercury.  The 
baryta  was  decomposed,  and  its  barium  combined  with  mercury. 

An  amalgam  was  obtained,  from  which  the  mercury  was  separated 
by  heat  in  a vessel  free  from  air,  and  barium  was  left  in  a pure  form. 

873.  It  is  a dark  gray  colored  metal,  with  a lustre  inferior  to  that  Properties. 


* For  other  methods  see  Henry’s  Chemistry , 1.  572. 

+ For  an  analysis  of  lithion  micas  and  the  distinguishing  properties  of  lithia,  see 
Turner’s  papers,  Edin . Jour.  iii.  137,  261,  &c. ; and  lor  Berzelius’  method  ol  disco- 
vering lithia  in  any  solution,  see  Edin.  Philos.  Jour.  iv.  128. 

Chloride  of  Lithium.  L+CL,  or  LC1,  6.44  1 eq.  lith.  + 35.42  1 eq.  chlo.  = 41.86 
equiv. 

Fluoride  of  Lithium.  L+F,  or  LF,  6.44  1 eq.  lith. + 18-68  1 eq.  flu.  =25.12  equiv. 


1 


238 


Metals — Barium. 


Chap.  IV. 
Protoxide. 

How  ob- 
tained. 


Properties. 


Solution. 


Affinity  for 

carbonic 

acid, 


Exp. 


Takes  it 
from  other 
bodies. 
Exp. 


Alkaline 

properties. 


of  cast-iron.  It  is  far  denser  than  water  and  sinks  in  sulphuric  acid. 
It  greedily  absorbs  oxygen  and  is  converted  into  baryta. 

874.  Protoxide  of  Barium , Ba-f-O,  Ba,  or  BaO,  68.7  1 eq.  bar. 
+ 8 1 eq.  oxy.  = 76.7  equiv.,  Barytes , or  Baryta , so  called  from 
the  great  density  of  its  compounds,  (from  ficiQvs,  heavy,)  was  disco- 
vered in  the  year  1744  by  Scheele.  It  is  the  sole  production  of  the 
oxidation  of  barium  in  air  and  water.  It  is  obtained  by  exposing  the 
crystals  of  nitrate  of  baryta  for  some  time  to  a bright  red  heat.  It 
may  also  be  obtained  by  decomposing  the  native  carbonate  of  baryta. 

Let  this  be  powdered,  and  passed  through  a fine  sieve.  Work  it  up  with  about 
an  equal  bulk  of  wheaten  flour  or  tar  into  a ball,  adding  a sufficient  quantity  of 
water.  Fill  a crucible  of  proper  size,  about  one  third  its  height,  with  powdered 
charcoal ; place  the  ball  on  this  ; and  surround  and  cover  it  with  the  same  pow- 
der, so  as  to  prevent  its  coming  into  contact  with  the  sides  of  the  crucible.  Lute 
on  a cover ; and  expose  it,  for  two  hours,  to  the  most  violent  heat  that  can  be 
raised  in  a wind  furnace.  Let  the  ball  be  removed  when  cold.  On  the  addition 
of  water,  it  will  evolve  great  heat,  and  the  baryta  will  be  dissolved.  The  fil- 
tered solution,  on  cooling,  will  shoot  into  beautiful  crystals.* 

875.  Baryta  is  of  a gray  colour,  and  very  difficult  of  fusion.  Its 
sp.  gr.  is  about  4,  being  the  heaviest  of  the  substances  usually  called 
earths.  It  eagerly  absorbs  water,  and  slakes  like  lime.  A white 
hydrate  is  formed,  composed  of  76.7  parts,  1 eq.  of  baryta,  and  9 
parts  or  1 eq.  of  water. 

876.  Hydrate  of  baryta  dissolves  in  three  times  its  weight  of  boil- 
ing water,  and  in  twenty  parts  of  water  at  the  temperature  of  60°  F.f 
A saturated  solution  of  baryta  in  boiling  water  deposits,  in  cooling, 
transparent,  flattened  prismatic  crystals,  which  are  composed  of  76.7 
parts  or  one  equivalent  of  baryta,  and  90  parts  or  10  equivalents  of 
water. 

The  aqueous  solution  of  baryta  is  an  excellent  test  of  the  presence 
of  carbonic  acid  in  the  atmosphere  or  in  other  gaseous  mixtures. 
The  carbonic  acid  unites  with  the  baryta,  and  a white  insoluble  pre- 
cipitate, carbonate  of  baryta,  subsides. 

Let  a solution  of  pure  baryta  be  exposed  to  the  atmosphere.  It  will  soon  be 
covered  with  a thin  white  pellicle  ; which,  when  broken,  will  fall  to  the  bottom 
of  the  vessel,  and  be  succeeded  by  another.  This  may  be  continued,  till  the 
whole  of  the  baryta  is  separated.  The  effect  arises  from  the  absorption  of  Car- 
bonic acid,  which  is  always  diffused  through  the  atmosphere,  and  which  forms, 
with  baryta,  a substance,  viz.  carbonate  of  baryta,  much  less  soluble  than  the 
pure  earth. 

Or  if  the  air  from  the  lungs  be  blown,  by  means  of  a quill,  or  tube^  through  a 
solution  of  baryta,  the  solution  will  immediately  become  milky,  in  consequence 
of  the  production  of  an  insoluble  carbonate.  The  same  effect  will  be  produced 
by  mingling  with  a solution  of  pure  baryta,  a little  water,  impregnated  with  car- 
bonic acid. 

877.  Baryta  has  so  strong  an  affinity  for  carbonic  acid  as  even  to 
take  it  from  other  bodies. 

If  to  a solution  of  a small  portion  of  carbonate  of  potassa,  of  soda,  or  of  ammo- 
nia we  add  the  solution  of  baryta,  the  earth  will  detach  the  carbonic  acid  from 
the  alkali,  and  will  fall  down  in  the  state  of  a carbonate.  By  adding  a sufficient 
quantity  of  a solution  of  baryta  in  hot  water,  the  whole  of  the  carbonic  acid  may 
thus  be  removed  from  a carbonated  alkali.  H.  1.  578. 

878.  As  baryta,  like  the  alkalies,  converts  vegetable  blues  to 
green,  and  serves  as  an  intermedium  between  oil  and  water,  it  has 


* For  other  processes  see  Sulphate  and  Nitrate  of  Baryta.  + Davy. 


Strontium. 


239 


been  called  an  alkaline  earth.  It  has  a very  acrid,  caustic  taste,  and  Sect,  m. 
is  highly  poisonous.  It  exists  in  two  natural  combinations  only,  viz. 
as  sulphate  and  carbonate. 

879.  Peroxide  of  Barium.  Ba-f-20,  or  BaOa-f-6Aq,  68.7  1 eq.  peroxide. 
bar.  -f-  16  2 eq.  oxy.  = 84.7  equiv.  When  dry  oxygen  gas  is  con- 
ducted over  pure  baryta  at  a low  red  heat  this  oxide  is  formed.  It 

is  employed  in  preparing  peroxide  of  hydrogen,  page  134.  An  easier  Process 
process  is  to  heat  pure  baryta  to  low  redness  in  a platinum  cruci-  v 
ble,  and  then  gradually  to  add  chlorate  of  potassa  in  the  ratio  of 
about  one  part  of  the  latter  to  four  of  the  former. 

880.  The  oxygen  of  the  chlorate  goes  over  to  the  baryta,  and  Theory 
chloride  of  potassium  is  generated.  Cold  water  removes  the  chlo- 
ride and  the  peroxide  of  barium  is  left  as  a hydrate  with  6 eq.  of 
water. 

881.  Chloride  of  Barium . Ba-j-Cl,  or  BaCl,  68.7  1 eq.  bar.  -f- 
35.42  1 eq.  chlor.  = 104.12.  Chloride  of  Barium  may  be  obtained  Chloride, 
by  heating  baryta  in  chlorine,  in  which  case  oxygen  is  evolved  : or, 

more  easily,  by  dissolving  carbonate  of  baryta  in  diluted  hydrochlo- 
ric acid.  When  filtered  and  evaporated,  the  solution  yields  regular 
crystals,  which  have  most  commonly  the  shape  of  flat  four  sided  ta- 
bles, very  like  those  of  heavy  spar.  They  contain  104.12  or  1 eq. 
of  chloride  of  barium  and  18  parts  or  2 eq.  of  water  ; formula  BaCl 
-|-2Aq.  100  parts  of  water  dissolve  43.5  at  60°,  and  78  at  222° 
which  is  the  boiling  point  of  the  solution.^ 

882.  Protosulphuret  of  Barium}  Ba-f-S  or  Bas,  68.7  1 eq.  bar.  sulphuret. 
-f-  16.1  1 eq.  sulp.  = 84.8  equiv.,  is  formed  when  dry  hydrosul- 
phuric  acid  gas  is  passed  over  pure  baryta  at  a red  heat,  and  by 

the  action  of  hydrogen  gas  or  charcoal  on  sulphate  of  baryta  (818.) 

It  is  very  soluble  in  hot  water,  and  the  solution  supplies  a ready 
mode  of  obtaining  pure  baryta  and  its  salts,  when  the  carbonate  can-  So^utlon- 
not  be  obtained.  Thus  its  solution,  boiled  with  black  oxide  of  cop- 
per until  it  ceases  to  precipitate  a salt  of  lead  black,  yields  pure  bary- 
ta, which  should  be  filtered  while  hot  to  separate  the  sulphuret  of 
copper  : it  is  apt  to  retain  traces  of  oxide  of  copper.  With  a solu- 
tion of  carbonate  of  potassa,  carbonate  of  baryta  falls,  and  sulphuret 
of  potassium  remains  in  solution  ; and  with  hydrochloric  acid  it  in- 
terchanges elements,  by  which  hydrosulphuric  acid  and  chloride  of 
barium  are  formed.  T. 


Strontium. 

Symb.  Sr  Equiv.  43.8 

883.  This  metal  was  discovered  by  Davy  in  strontia , by  the  same  Discovery, 
process  as  barium,  which  it  resembles. 

884.  Protoxide  of  Strontium , Sr-f-0,  Sr,  or  SrO,  43.8  1 eq.  Strontia. 
stron.  -f-  8 1 eq.  oxy.  = 51.8  equiv.,  or  the  earth  Strontia , is  so 


* Iodide  of  Barium.  Ba+I,  or  Bal,  68.7  1 eq.  bar.  + 126.3  1 eq.  iod.  = 195  equiv.  iodide. 

Bromide  of  Barium.  Ba+Br,  or  BaBr,  68.7  1 eq.  bar.  + 78.4  1 eq.  brom.  = 

147.1  equiv. 

Fluoride  of  Barium.  Ba+F,  or  BaF,  68.7  1 eq.  bar.  + 18.68  1 eq.  flu.  =87.38 


240 


Metals — Calcium . 


ChaP- IV-  called  from  Strontian  in  Scotland,  where  it  was  first  discovered  in 
combination  with  carbonic  acid. 


How  ob- 
tained. 


Composi- 

tion. 

Properties. 


Salts. 


Chloride. 


It  may  be  prepared  either  by  subjecting  the  carbonate  to  a strong  heat  in  a 
crucible,  or  by  igniting  the  nitrate  in  a porcelain  retort  or  other  close  vessel.  A 
gray  substance  remains  which  becomes  very  hot  on  the  affusion  of  water  ; and 
when  more  water  is  added  and  heat  applied,  a considerable  proportion  of  the 
earth  is  dissolved.  On  cooling,  the  solution  deposits  regular  crystals;  but  the 
shape  of  these  differs  considerably  from  that  of  barytic  crystals. 

The  crystals  of  strontia  are  thin  quadrangular  plates. 

885.  The  hydrate  consists  of  51.8  parts  or  1 eq.  of  strontia,  and 
9 parts  or  1 eq.  water.  The  crystals  contain  10  eq.  water  and  1 
strontia.  It  requires  50  times  its  weight  of  water  for  solution. 

886.  Pure  strontia  has  a pungent,  acrid  taste,  and  when  powder- 
ed in  a mortar,  the  dust  that  rises  irritates  the  lungs,  and  nostrils. 
Its  specific  gravity  approaches  that  of  baryta. 

887.  The  salts  of  strontia  are  best  prepared  from  the  native  car- 
bonate. Like  those  of  baryta,  they  are  precipitated  by  alkaline  car- 
bonates, and  by  sulphuric  acid  or  soluble  sulphates.  But  sulphate 
of  strontia  is  less  insoluble  than  sulphate  of  baryta : on  adding  sul- 
phate of  soda  in  excess  to  a barytic  solution,  baryta  cannot  after- 
wards be  found  in  the  liquid  by  any  precipitant;  but  when  strontia 
is  thus  treated,  so  much  sulphate  of  strontia  remains  in  solution, 
that  the  filtered  liquid  yields  a white  precipitate  with  carbonate  of 
soda.  The  salts  of  strontia  are  not  poisonous  ; and  most  of  them, 
when  heated  on  platinum  wire  before  the  blow-pipe,  communicate 
to  the  flame  a red  tint.* 

888.  Chloride  of  Strontium,  Sr— (—Cl,  or  SrCl,  43.8  1 eq.  stron. 
-f-  35.42  1 eq.  chlor.  — 79.22  equiv.  This  compound  is  formed  by 
processes  similar  to  those  for  preparing  chloride  of  barium,  and  crys- 
tallizes in  colourless  prismatic  crystals,  which  deliquesce  in  a moist 
atmosphere,  require  only  twice  their  weight  of  water  at  60°  for  so- 
lution, and  still  less  of  boiling  water,  and  are  soluble  in  alcohol. 
The  alcoholic  solution,  when  set  on  fire,  burns  with  a red  flame. 
These  characters  afford  a certain  mode  of  distinguishing  strontia 
from  baryta.  The  crystals  consist  of  79.22  parts  or  1 eq.  of  chloride 
of  strontium,  and  81  parts  or  9 eq.  of  water,  which  are  expelled  by 
heat.  The  anhydrous  chloride  fuses  at  a red  heat,  and  yields  a 
white  crystalline  brittle  mass  on  cooling.! 


Calcium. 


Symb.  Ca  Eq.  20.5 

How  ob-  8S9.  When  lime  is  electrized  negatively  in  contact  with  mercury, 
tained.  an  amalgam  is  obtained,  which,  by  distillation,  affords  a white  met- 


* Peroxide  of  Strontium,  Sr+20  or  SrO2.  43  S 1 eq.  stron.  + 16  2 eq.  oxy  = 59.8 
eroxide.  equiv.,  is  prepared  in  the  same  way  as  peroxide  of  barium,  and  like  it,  is  resolved 
by  dilute  acids  into  strontia  and  oxygen,  the  latter  of  which  forms  peroxide  of  hydro- 
gen with  the  water. 

iodide.  t Iodide  of  Strontium,  Sr+I,  or  Sri,  43.8  1 eq.  stron.  + 126.3  1 eq.  iod.  = 170.1 

equiv.,  may  be  prepared  in  the  same  manner  as  that  of  barium.  It  is  very  soluble  in 
water. 

Fluoride  of  Strontium  and  Protosulphur et  of  Strontium , Sr+F  or  SrF,  43.8  1 eq. 
stron.  -|-  18.68  1 eq.  fluor.  = 62.48  equiv.  and  Sr-fS  or  SrS,  43.8  1 eq.  stron.  16.1 
l eq.  sulp.  = 59.9  equiv.  are  obtained  like  those  of  barium. 


Lime  Watfir. 


241 


al.  It  has  been  called  calcium , and  when  exposed  to  air,  and  gently  Sect,  m. 
heated,  it  burns  and  produces  the  oxide  of  calcium  or  lime. 

890.  Protoxide  of  Calcium , Ca-j-O,  Ca,  or  CaO,  20.5  1 eq.  calc.  Protoxide 

8 1 eq.  oxy.  = 28.5  equiv.  This  compound,  commonly  known  by  " 

the  name  of  lime  and  quicklime , is  obtained  by  exposing  carbonate 

of  lime  to  a strong  red  heat,  so  as  to  expel  its  carbonic  acid.  If  lime 
of  great  purity  is  required,  it  should  be  prepared  from  pure  carbonate 
of  lime,  such  as  Iceland  spar  or  Carrara  marble.  Its  colour  is  gray, 
it  is  acrid  and  caustic  ; its  sp.  gr.  is  about  2.3. 

891.  It  is  very  difficult  of  fusion,  but  remarkably  promotes  the  Fusibility, 
fusion  of  most  other  earthy  bodies,  and  is  therefore  used  in  several 
metallurgic  processes  as  a cheap  and  powerful  flux.  When  quite 

pure  it  can  only  be  fused  in  very  minute  particles  by  the  oxy-hydro- 
gen  blow-pipe,  or  by  the  Voltaic  flame.  It  is  an  essential  ingredient  in  Uses 
mortar,  and  other  cements  used  in  building.  Exposed  to  air  it 
becomes  white  by  the  absorption  of  water  and  a little  carbonic  acid. 

892.  It  has  a powerful  affinity  for  water.  When  a small  quantity 
of  water  is  poured  upon  lime,  there  is  a great  rise  of  temperature 
resulting  from  the  solidification  of  a portion  of  the  water,  and 
white  powder  is  obtained,  called  slaked  limey  which  is  a hydrate , and 
appears  to  consist  of  one  eq.  water  = 9-f-one  eq.  lime  = 28.5. 

Some  care  is  necessary  in  its  preparation,  lest  more  water  should 
be  added,  than  is  essential  to  its  constitution.  It  affords  a very  con- 
venient form  of  keeping  lime,  for  occasional  use  in  a laboratory  ; 
for  the  hydrate  may  safely  be  preserved  in  glass  bottles,  which  are 
almost  constantly  broken  by  the  earth,  if  enclosed  in  its  perfectly 
dry  state. 

893.  The  degree  of  heat  produced  by  the  combination  of  lime  Heat, 
with  water,  is  supposed  by  Dalton  to  be  not  less  than  800°,  and  is 
sufficient  to  set  fire  to  some  inflammable  bodies. 

Place  a large  lump  of  well  burned  quicklime  on  an  iron  dish  and  add  Exp. 
a small  quantity  of  water,  a piece  of  phosphorus  resting  on  it  will  be  ignited. 


Hydrate. 


When  a large  quantity  of  lime  is  suddenly  slaked  in  a dark  place, 
even  light,  according  to  Pelletier,  is  sometimes  evolved. 

894.  When  a sufficient  quantity  of  water  has  been  added  to  re-  Milk  of 
duce  lime  into  a thin  liquid,  this  is  called  milk  or  cream  of  lime. 

By  the  addition  of  more  water  the  solution  known  as  lime  water  Water  of, 
is  obtained.  When  sufficiently  cool  it  should  be  poured  into  a well 
stopped  bottle  until  the  undissolved  parts  have  subsided,  and  be  then 
decanted  and  kept  from  the  air. 

Lime  is  very  sparingly  soluble  in  water,  viz.  in  the  proportion  of 
about  1 to  778.* 

895.  Lime-water  is  limpid  and  colourless  ; its  taste  is  nauseous,  ^Fr^ies 
acrid,  and  alkaline,  and  it  converts  vegetable  blues  to  green.  When  water. 
exposed  to  the  air,  a pellicle  of  carbonate  of  lime  forms  upon  its  sur- 
face, which,  if  broken,  is  succeeded  by  others,  until  the  whole  of  the 


* According  to  Thomson  1 to  75S.  The  experiments  of  Dalton  tend  to  establish  a 
curious  fact  respecting  the  solubility  of  lime,  viz.  that  it  dissolves  more  plentifully 
in  cold  than  in  hot  water  5 he  found  that  at  60°  F.  778  grains  of  water  dissolve  l grain 
of  lime,  and  at  212°,  1270  grains  were  required.  He  further  infers  that  at  the  freezing 
point  water  would  probably  take  up  nearly  twice  as  much  lime  as  is  dissolved  by 
boiling  water — this  has  been  confirmed  by  Phillips. — Ann.  Philos.  N.  S.  1.  107. 

31 


242 


Metals — Calcium. 


Uses. 


Exp. 


Test  of. 


Chap.  iv.  lime  is  thus  separated  in  the  form  of  an  insoluble  carbonate.  It  is 
used  in  medicine  as  an  antacid,  and  is  a good  test  of  the  presence 
of  carbonic  acid  gas. 

Into  transparent  lime  water  pass  carbonic  acid,  or  breathe  into  it  by  means  of 
a glass  tube,  it  will  become  milky  and  opaque  from  the  formation  of  carbonate 
of  lime.  If  an  excess  of  carbonic  acid  is  added  the  carbonate  is  dissolved  and 
transparency  restored. 

896.  The  most  delicate  test  of  the  presence  of  lime  is  oxalate  of 
ammonia  or  potassa  ; for  of  all  the  salts  of  lime,  the  oxalate  is  the 
most  insoluble  in  water.  This  serves  to  distinguish  lime  from  most 
substances,  though  not  from  baryta  and  strontia  ; because  the  oxa- 
lates of  baryta  and  strontia,  especially  the  latter,  are  likewise  spar- 
ingly soluble.* 

Chloride  of  897.  Chloride  of  Calcium , Ca-f-Cl,  or  CaCl,  20.5  1 eq.  calc. 
calcium.  35.42  1 eq.  chlor.  = 55.92  equiv.,  is  produced  by  heating  lime  in 
chlorine,  in  which  case  oxygen  is  evolved ; or  by  evaporating  hydro- 
chlorate of  lime  to  dryness,  and  exposing  the  dry  mass  to  a red  heat 
in  close  vessels.  In  this  case  the  hydrochloric  acid  is  decomposed  ; 
its  hydrogen  uniting  with  the  oxygen  of  the  lime,  escapes  in  the 
state  of  water  ; and  the  chlorine  unites  with  the  calcium. 

S98.  This  compound  has  a strong  attraction  for  water ; it  deli- 
quesces when  exposed  to  the  air,  and  becomes  what  used  to  be  cal- 
led oil  of  lime.  It  is  difficultly  crystallizable  from  its  aqueous  solu- 
tion ; with  care,  however,  it  may  be  obtained  in  irregular  prisms, 
consisting  of  55.92  parts  or  1 eq.  of  chloride  of  calcium,  and  54 
parts  or  6 eq.  water.  Its  taste  is  bitter  and  acrid  ; one  part  of  water 
at  60°  dissolves  four  parts  of  the  chloride.  Its  solubility,  however, 
is  greatly  influenced  by  temperature.  It  is  copiously  soluble  in  al- 
cohol, and  much  heat  is  evolved  during  the  solution.  When  fused 
it  acquires  a phosphorescent  property  as  was  first  observed  by  Hom- 
Homberg’s  berg,  and  is  hence  termed  Homberg's  phosphorus.  It  is  abundantly 
phospho-  produced  in  the  manufacture  of  carbonate  of  ammonia,  from  the 
decomposition  of  hydrochlorate  of  ammonia  by  lime. 

899.  It  is  used  for  frigorific  mixtures  with  snow,  and  for  this  pur- 
pose the  hydrous  chloride  is  preferable,  prepared  by  evaporating  its 
solution  so  far  that  the  whole  becomes  a solid  mass  on  removal  from 
the  fire.  It  should  be  kept  in  bottles  well  secured  from  the  air. 

In  its  fused  state  this  compound  is  very  useful  for  drying  certain 
gaseous  bodies,  but  where  the  quantity  of  the  gas  is  to  be  ascertain- 
ed, its  powers  of  absorption  in  certain  cases  must  not  be  overlooked. 

Pelletier  has  stated,  that  if  carbonic  acid  be  passed  through  a solu- 
tion of  hydrochlorate  of  lime,  the  whole  becomes  a hard  solid  mass. 
If  sulphuric  acid  be  poured  into  a strong  solution  of  hydrochlorate  of 
lime,  the  whole  congeals  into  a solid  mass  of  sulphate  of  lime  (61). 


Composi- 
tion and 
properties. 


Uses. 


* All  these  oxalates  dissolve  readily  in  water  acidulated  with  nitric  or  hydrochloric 
acid.  It  is  distinguished  from  baryta  and  strontia  by  the  fact,  that  nitrate  of  lime 
yields  prismatic  crystals  by  evaporation,  is  deliquescent  in  a high  degree,  and  very 
so’uble  in  alcohol  j while  the  nitrates  of  baryta  and  strontia  crystallize  in  regular 
octohedrons  or  segments  of  the  octohedron,  undergo  no  change  on  exposure  to  the  air, 
except  when  it  is  very  moist,  and  do  not  dissolve  in  pure  alcohol.  T. 

Peroxide  of  Calcium.  Ca+20,  or  CaO2,  20.5  1 eq.  calc.  + 16  2 eq.  oxy.  = 36.6 
equiv.  It  is  prepared  in  the  same  way  as  peroxide  of  barium,  and  is  similar  in  its 
properties. 


Bleaching  Powder. 


243 


900  It  absorbs  large  quantities  of  ammoniacal  gas,  during  which  Sect,  m. 
it  swells,  cracks,  and  at  last  crumbles  down  into  a white  powder.  Absorbs 
With  water  it  forms  a strong  alkaline  solution.  Heated  it  gives  ofTamrnon*a- 
ammonia  and  the  chloride  remains.  Immersed  in  chlorine,  the  am- 
monia burns  off  with  a pale  yellow  flame.  Twenty  grains  of  the 
compound  furnish,  when  heated,  about  20  cubic  inches  of  ammonia ; 

Faraday  availed  himself  of  it  for  the  liquefaction  of  ammonia.* 

901.  The  chloride  of  lime  is  abundantly  employed  as  a bleaching  Bleachi 
material,  and  known  by  the  name  of  bleaching  powder  ; it  is  manu-  powder.  g 
factured  by  passing  chlorine  into  leaden  chambers  containing  hy- 
drate of  lime  in  fine  powder,  by  which  the  gas  is  copiously  absorbed 
with  evolution  of  heat.  When  heated  it  gives  off  a large  quantity  of 
oxygen,  and  a chloride  of  calcium  results,  showing  the  superior  at- 
traction of  calcium  for  chlorine  compared  to  oxygen,  the  latter  being 
expelled  from  the  lime. 

The  composition  of  bleaching  powder  has  been  variously  stated.  Composi- 
Dalton  considers  it  as  a hydrated  subchloride  of  lime,  containing  two  tion° 
proportions  of  lime  and  one  of  chlorine  ;t  and  the  same  opinion  is 
adopted  by  Thomson,!  and  by  Welter.^  According  to  Urell  the 
quantity  of  chlorine  absorbed  is  variable.  That  manufactured  at 
Glasgow  is  stated  by  Thomson  to  be  a compound  of  one  atom  of  chlo- 
rine and  one  of  lime. If 


* Faraday  in  Jour.  Roy • Inst.  v.  74.  IfAnn.  of  Philos,  i.  15  and  ii.  6.  £ lb.  xv.  401. 


§Ann.  de  Chim.  et  Phys.  vii.  383.  ||  Quart.  Jour.  xiii.  21. 

IT  As  the  value  of  chloride  of  lime  depends  on  the  quantity  of  chlorine  which  it  con- 
tains, and  as  this  varies  considerably,  several  methods  for  ascertaining  its  strength 
have  been  proposed.  One  consists  in  adding  a given  quantity  of  the  diluted  solution 
to  a solution  of  indigo  in  sulphuric  acid  of  a known  strength  ;■*.  the  strength  of  the 
chlorine  being  indicated  by  the  quantity  of  the  solution  which  it  can  decolorize.  Mo- 
rin has  proposed  a solution  of  the  hydrochlorate  of  manganese  as  a substitute  for  this, 
as  giving  more  accurate  indications,  the  lime  combining  with  the  hydrochloric  acid, 
and  precipitating  the  brown  oxide  of  manganese,  while  the  chlorine  is  disengaged  5 
the  quantity  of  the  hydrochlorate  decomposed  corresponding  with  the  chlorine  set  at 
liberty. f It  has  also  been  proposed  to  ascertain  the  quantity  of  chlorine  by  observing 
the  quantity  of  nitrogen  gas  which  is  disengaged  when  it  is  made  into  a paste  or 
cream  with  water  and  mixed  with  fragments  of  hydrochlorate  of  ammonia ; the  lime 
combining  with  the  hydrochloric  acid  and  forming  hydrochlorate  of  lime,  while  the 
chlorine  takes  hydrogen  from  the  ammonia  and  disengages  nitrogen  (420). 

An  instrument  for  the  speedy  analysis  of  this  substance  has  been  described  by  Ure.t 
It  consists  of  a glass  tube,  (Fig.  178,)  of  about  five  cubic  inches  capa-  Fig  178. 
city,  graduated  into  cubic  inches  and  tenths.  It  is  closed  at  top  with  a 
brass  screw  cap,  and  at.  its  recurved  end  below,  with  a good  cork.  Pour 
mercury  into  the  upper  orifice,  till  the  tube  be  nearly  full,  leaving 
merely  space  to  insert  ten  grains  of  the  bleaching  powder,  made  into  a 
pellet  form  with  a drop  of  water.  Screw  in  the  cap-plug  rendered  air- 
tight by  leather.  Remove  now  the  cork  from  the  lower  end,  (also  full 
of  mercury,)  and  replace  a little  of  the  liquid  metal  by  dilute  hydro- 
chloric acid  (sp.  gr.  l.l).  By  dexterous  inclination  of  the  instrument, 
the  acid  is  made  to  flow  up  through  the  mercury.  Instantly  on  its  co- 
ming in  contact  with  the  pellet,  the  chlorine  is  disengaged,  the  mercury 
flows  out  into  a basin  ready  to  receive  it,  while  the  resulting  film  of 
hydrochlorate  of  lime  protects  the  surface  of  the  metal  almost  com- 
pletely from  the  gas. 

The  same  instrument  may  be  employed  for  ascertaining  the  quantity 
of  carbonic  acid  in  limestone,  &c.§ 

Estimating  a cubic  inch  of  chlorine  in  round  numbers  at  I of  a grain,  we  may  expect 
10  grains  of  bleaching  powder  to  yield  from  3 to  4 cubic  inches  of  that  gas,  or  by 
weight,  from  20  to  30  per  cent.  Ure. 


Ure’s  method 
of  analysis. 


* As  the  quantity  of  indigo  varies,  this  test  cannot  be  relied  upon.  See  Amer-  Jour.  xvii.  170. 


f Jour.  Roy.  Inst.  vi.  J Jour.  Roy.  Inst.  xiii.  21.  $See  Ure’s  Chem  Diet,  article  Carbonate. 


244 


Metals — Calcium. 


Chap,  iv.  902.  Fluoride  of  Calcium — Fluor  Spar.  Ca-f-F,  or  CaF,  20.5 
1 eq.  cal.  -f-  18.68  1 eq.  flu.  = 39.18  equiv.  Fluor  spar  is  a 
mineral  found  in  many  parts  of  the  world,  but  in  great  beauty 
and  abundance  in  England,  and  especially  in  Derbyshire.  Here 
it  is  commonly  called  Derbyshire  spar , or  by  the  miners  of  that 
Fluor  spar,  county  blue  John*  It  is  usually  found  in  cubic  crystals,  which 
may  easily  be  cleaved  into  octohedra,  sometimes  considered  as  its 
primitive  form.  Its  colours  are  extremely  various.  Its  specific 
gravity  is  3.15.  It  is  perfectly  tasteless  and  insoluble  in  water. 
When  thrown  in  powder  upon  a plate  of  iron  heated  below  redness 
in  a dark  place,  it  emits  a phosphorescent  light.! 

Properties.  903.  piuorjde  0f  calcium  fuses  at  a red  heat  without  farther 
change.  It  is  insoluble  in  water,  slightly  soluble  in  hot  diluted  hy- 
drochloric acid,  and  is  decomposed  by  sulphuric  acid  aided  by  gentle 
heat,  affording  hydrofluoric  acid  (715).! 

Protosul’  904  Protosulphur et  of  Calcium.  Ca-(-S,  or  CaS,  20.5  1 eq.  cal. 
phuret.  16.1  1 eq.  sulph.  = 36.6  equiv.  This  compound  may  be 

prepared  by  reduction  from  the  sulphate  by  hydrogen  or  charcoal, 
and  when  pure  is  white  with  a reddish  tint,  and  is  very  sparingly 
soluble  in  water.  It  has  the  property,  in  common  with  sulphuret 
of  barium,  of  being  phosphorescent  after  exposure  to  light,  and 
appears  to  be  the  essential  ingredient  of  Canton’s  phosphorus. 

When  3 parts  of  slaked  lime,  I of  sulphur,  and  20  of  water,  are 
retU  PhU  boiled  together  for  an  hour,  and  the  solution,  without  separation  from 
the  sediment,  is  set  aside  in  a corked  flask  for  a few  days,  a copious 
deposite  of  orange-coloured  crystals  takes  place,  which,  when  slowly 
formed,  are  flat  quadrilateral  prisms.  These,  from  the  analysis  of 
Herschel,§  appear  to  be  bisulphuret  of  calcium  with  3 eq.  of  water. 
They  are  decomposed  by  exposure  to  the  air,  and  are  of  sparing  so- 
lubility in  water. 

When  either  of  the  foregoing  sulphurets  is  boiled  in  water  along 
with  sulphur,  a yellow  solution  is  formed  containing  calcium  com- 
bined with  five  equivalents  of  sulphur.|| 

905.  Phosphuret  of  Calcium.  Ca-j-P,  or  CaP,  20.5  1 eq.  cal.  -f- 
Phosphu-  15.7  1 eq.  phos.  = 36.2  equiv.  It  is  formed  by  passing  the 
Tet*  vapour  of  phosphorus  over  fragments  of  quicklime  at  a low  red 

heat  ;1T  when  a brown  matter  is  formed,  consisting  of  phosphate  of 


* It  occurs  in  various  parts  of  the  United  States— that  from  Shawneetown,  Illinois,  is 
particularly  beautiful.  For  other  localities  see  Cleaveland’s  and  Dana’s  Mineralogy. 

t It  may  be  prepared  artificially  by  digesting  moist,  recently  precipitated,  carbonate 
Proceu.  jjme  jn  au  excess  0f  hydrofluoric  acid  ; or  by  mixing  a solution  of  chloride  of  calci- 

um with  fluoride  of  potassium  or  sodium.  As  prepared  in  the  latter  mode,  it  is  a 
bulky  gelatinous  mass,  which  it  is  very  difficult  to  wash  ; whereas  the  former  method 
gives  it  in  the  state  of  a granular  white  powder,  which  may  be  washed  with  ease. 

t Iodide  of  Calcium.  Ca+I,  or  Cal,  20.5  l eq.  cal.+126.3  1 eq.  iod.  = 146.8  equiv. 

Bromide'  of  Calcium.  Ca+Br.  or  CaBr,  20.5  1 eq.  cal.  + 78.4  1 eq.  brom.  = 
93.9  equiv.  § Edin.  Philos.  Jour.  1.  p.  11,  &c. 

||  Bisulphuret  of  Calcium.  Ca+2S,  or  CaS*,  20.5  1 eq.  cal.  + 32.2  2 eq.  sulph.  = 
52.7  equiv. 

Quintosulphurel  of  Calcium.  Ca+5S,  or  CaS5,  20.5  1 eq.  cal.  + 80.5  5 eq.  sulph. 
= 101  equiv. 

„ if  Select  a green  glass,  or  porcelain  tube, closed  at  one  end,  and  about  18  inches  long, 

How  prepared.  ^ ^ diameter)  and  carefully  cover  it  with  a clay  lute  containing  a very  little 


Magnesium . 

lime  and  phosphuret  of  calcium.  When  put  into  water,  mutual  Sect- I1L 
decomposition  ensues,  and  phosphuretted  hydrogen,  hypophospho- 
rous  acid,  and  phosphoric  acid  are  generated  (777). 

Drop  a small  piece  of  it  into  a wine-glass  of  water,  and  in  a short  time  bubbles  Exp. 
of  phosphuretted  hydrogen  gas  will  be  produced ; which,  rising  to  the  sur- 
face will  take  fire,  and  explode.  If  the  phosphuret  of  lime  be  not  perfectly  fresh, 
it  may  be  proper  to  warm  the  water  to  which  it  is  added. 

Into  an  ale-glass  put  one  part  of  the  phosphuret  in  pieces  of  about  the  size  of  Exp. 
a pea  (not  in  powder),  and  add  to  it  half  a part  of  chlorate  of  potassa.  Fill  the 
glass  with  water,  and  put  into  it  a funnel,  with  a long  pipe,  or  narrow  glass  tube, 
reaching  to  the  bottom.  Through  this  pour  three  or  four  parts  of  strong  sulphu- 
ric acid,  which  will  decompose  the  chlorate ; and,  the  phosphuret  also  decom- 
posing the  water  at  the  same  time,  flashes  of  fire  dart  from  the  surface  of  the  fluid, 
and  the  bottom  of  the  vessel  is  illuminated  by  a beautiful  green  light. 

Magnesium. 

Symb.  Mg  Equiv.  12.7* 

906.  The  existence  of  this  metal  was  demonstrated  by  Davy,  but  DiSC0Very. 
it  was  first  obtained  in  any  quantity  by  Bussy,  in  1830  by  means  of 
potassium. 

907.  For  this  purpose  five  or  six  pieces  of  potassium,  of  the  size  of  peas,  were  process  for. 
introduced  into  a glass  tube,  the  sealed  extremity  of  which  was  bent  into  the 

form  of  a retort,  and  upon  the  potassium  were  laid  fragments  of  chloride  of  mag- 
nesium. The  latter  being  then  heated  to  near  its  point  of  fusion,  a lamp  was 
applied  to  the  potassium,  and  its  vapour  transmitted  through  the  mass  of  heated 
chloride.  Vivid  incandescence  immediately  took  place,  and  on  putting  the  mass, 
after  cooling,  into  water,  the  chloride  of  potassium  with  undecomposed  chloride 
of  magnesium  was  dissolved,  and  metallic  magnesium  subsided.  These  results 
have  been  since  confirmed  by  Liebig.t 

908.  Magnesium  has  a brilliant  metallic  lustre,  and  a white  colour  properties. 
like  silver  ; is  very  malleable,  and  fuses  at  a red  heat.  Moist  air  ox- 
idizes it  superficially ; but  it  undergoes  no  change  in  dry  air,  and 

may  be  boiled  in  water  without  oxidation.  Heated  to  redness  in  air 
or  oxygen  gas,  it  burns  with  brilliancy,  yielding  magnesia ; and  it 
inflames  spontaneously  in  chlorine  gas.  It  is  readily  dissolved  by 
dilute  acids  with  disengagement  of  hydrogen,  and  the  solution  is 
found  to  contain  a pure  salt  of  magnesia. 

909.  Protoxide  of  Magnesium . MG-j-O,  Mg,  or  MgO,  12.7  1 


borax.  Put  an  ounce  of  phosphorus  broken  into  small  pieces  into  the  lower  end,  and 
fill  it  up  with  pieces  of  clean  quicklime,  about  the  size  or  large  peas  ; place  it  in  an  in- 
clined position  in  a furnace,  so  that  the  end  containing  the  phosphorus  may  protrude, 
while  the  upper  part  of  the  tube  is  heating  to  redness  5 then  slowly  draw  the  cool  part 
into  the  fire,  by  which  the  phosphorus  will  be  volatilized,  and  passing  into  the  red-hot 
lime,  convert  a portion  of  it  into  phosphuret.  Care  should  be  taken  that  no  conside- 
rable portion  of  phosphorus  escapes  and  burns  away  at  the  open  end  of  the  tube,  Properties, 
which  after  the  process,  should  be  corked  and  suffered  to  cool.  Its  contents  may  then 
be  shaken  upon  a sheet  of  paper,  and  the  brown  pieces  picked  out  and  carefully  pre- 
served in  a well  stopped  phial  3 the  white  pieces,  or  those  which  are  only  pale  brown, 
must  be  rejected. 

An  easier  method  is,  by  throwing  a piece  of  dry  phosphorus  into  a crucible  with 
a few  fragments  of  lime  (each  about  the  size  of  a pea),  at  the  bottom,  and  at  a bright 
red  heat,  an  assistant  putting  on  a cover,  or  inverting  it  immediately  on  a flat  plate  of 
iron,  at  the  same  time  throwing  a quantity  of  sand  round  it  to  close  any  aperture.  The 
experiment  may  be  made  with  20  or  30  grains  of  phosphorus,  and  about  60  or  70 
of  lime  in  a small  crucible.  R.  See  Mitchell’s  process,  page  218,  Note. 

* Inferred  by  Berzelius  from  the  quantity  of  sulphate  obtained  from  a known 
weight  of  pure  magnesia. 

t Ann.  de  Ckim.  et  de  Pkys.  xlvi.  435. 


246 


Chap.  IV. 

Protoxide 
or  magne- 
sia. 


Action  of 
water. 


Solution. 


Properties. 


Process. 


Calcined  mag- 
nesia. 


Metals — Magnesium. 

eq.  mag.  + 8 1 eq.  oxy.  = 20.7  equiv.  This,  the  only  known 
oxide  of  magnesium,  commonly  known  by  the  name  of  magnesia,  is 
best  obtained  by  exposing  carbonate  of  magnesia  to  a very  strong  red 
heat,  by  which  its  carbonic  acid  is  expelled.  It  is  a white,  friable 
powder,  of  an  earthy  appearance  ; and,  when  pure,  it  has  neither 
taste  nor  odour.  Its  specific  gravity  is  about  2.3,  and  it  is  exceed- 
ingly infusible.  Brande  once  succeeded  in  agglutinating  a small 
portion  of  this  earth  in  the  Voltaic  flame,  and  whilst  exposed  to  this 
high  temperature,  it  was  perfectly  fused  by  directing  upon  it  the 
flame  of  oxygen  and  hydrogen. 

910.  It  has  a weaker  affinity  than  lime  for  water;  for  though  it 
forms  a hydrate  when  moistened,  the  combination  is  effected  with 
hardly  any  disengagement  of  caloric,  and  the  product  is  readily  de- 
composed by  a red  heat.* 

Magnesia  dissolves  very  sparingly  in  water.  According  to  Fyfe, 
it  requires  5142  times  its  weight  of  water  at  60°,  and  36.000  of 
boiling  water  for  solution.  The  resulting  liquid  does  not  change 
the  colour  of  violets ; but  when  pure  magnesia  is  put  upon  moistened 
turmeric  paper,  it  causes  a brown  stain.  From  this  there  is 
no  doubt  that  the  inaction  of  magnesia  with  respect  to  vegetable  co- 
lours, when  tried  in  the  ordinary  mode,  is  owing  to  its  insolubility. 
It  possesses  the  still  more  essential  character  of  alkalinity,  that, 
namely,  of  forming  neutral  salts  with  acids,  in  an  eminent  degree.  It 
absorbs  both  water  and  carbonic  acid  when  exposed  to  the  atmos- 
phere, and,  therefore,  should  be  kept  in  well  closed  phials. 

911.  Magnesia  is  characterized  by  the  following  properties.  With 
nitric  and  hydrochloric  acid  it  forms  salts  which  are  soluble  in  alco- 
hol, and  exceedingly  deliquescent.  The  sulphate  of  magnesia  is  very 
soluble  in  water,  a circumstance  by  which  it  is  distinguished  from 
the  other  alkaline  earths.  Magnesia  is  precipitated  from  its  salts  as 
a bulky  hydrate  by  the  pure  alkalies.  It  is  precipitated  as  carbonate 
of  magnesia  by  the  carbonates  of  potassa  and  soda  ;t  but  the  bicar- 
bonates and  the  common  carbonate  of  ammonia  do  not  precipitate 
it  in  the  cold.  If  moderately  diluted,  the  salts  of  magnesia  are  not 
precipitated  by  oxalate  of  ammonia.  By  means  of  this  reagent 
magnesia  may  be  both  distinguished  and  separated  from  lime. 

912.  Chloride  of  Magnesium.  Mg-{-Cl,  or  MgCl,  12.7  1 eq.  mag. 

35.42  1 eq.  = 43.12  equiv.  This  may  be  prepared  by  trans- 
mitting dry  chlorine  gas  over  a mixture  of  magnesia  and  charcoal  at 
a red  heat ; but  Liebig  has  given  an  easier  process,  which  consists 
in  dissolving  magnesia  in  hydrochloric  acid,  evaporating  to  dryness, 
mixing  the  residue  with  its  own  weight  of  hydrochlorate  of  ammo- 
nia, and  projecting  the  mixture  in  successive  portions  into  a platinum 
crucible  at  a red  heat.  As  soon  as  the  ammoniacal  salt  is  wholly 
expelled,  the  fused  chloride  of  magnesium  is  left  in  a state  of  tranquil 

* The  native  hydrate  is  found  at  Hoboken,  N.  J.,  it  consists  of  70  magnesia  and  30 
water. 

+ The  carbonate  of  magnesia,  used  in  medicine,  and  for  experimental  purposes,  is 
prepared  by  mixing  hot  solutions  of  carbonate  of  potassa  and  sulphate  of  magnesia  (Ep- 
som salts).  The  carbonic  acid  is  expelled  by  moderate  heat,  and  the  residue  is  pure 
magnesia  ; being  prepared  by  calcination,  it  is  known  as  calcined  magnesia.  When 
incautiously  used  for  a long  time  it  may  produce  very  serious  evils,  a remarkable  case 
has  been  reported  by  Brande  in  Jour.  Roy.  Instil,  i. 


Aluminium . 


247 


fusion,  and  on  cooling  becomes  a transparent  colourless  mass,  which  Sect-  tv. 
is  highly  deliquescent,  and  is  very  soluble  in  alcohol  and  water. ^ 


Section  IV.  Metallic  Bases  of  the  Earths. 

913.  Aluminium . Al.  eq.  13.7.  Alumina  constitutes  some  of  the  Aluminous 
hardest  gems,  such  as  the  sapphire  and  ruby  ; and  combined  with  minerals- 
water,  it  gives  a peculiar  softness  and  plasticity  to  some  earthy  com- 
pounds, such  as  the  different  kinds  of  clay. — The  experiments  of 

Davy  afforded  a strong  presumption  that  alumina  is  a metallic  oxide ; Alumi- 
but  its  base,  aluminium , he  did  not  obtain  in  such  a state  as  to  nlum* * * § 
make  its  properties  an  object  of  investigation.  Yet  alloys  were 
formed  which  gave  sufficient  evidence  of  its  existence,  and  the 
presence  of  oxygen  in  alumina  was  proved,  by  its  changing  potas- 
sium into  potassa,  when  ignited  with  that  metal. 

914.  Aluminium  has  since  been  procured  by  Wohlert  by  decom- 
posing the  chloride  by  means  of  potassium.  The  action  is  very  vio- 
lent, and  accompanied  with  such  intense  heat  that  a crucible  of  pla-  Processfor” 
tinum  is  required. 

915.  The  aluminium  is  generally  in  small  scales  of  a metallic  properties, 
lustre,  or  in  slightly  coherent  spongy  masses  with  the  lustre  of  tin. 

It  conducts  electricity  in  its  fused  state,  but  in  the  form  of  powder 
it  does  not.  Its  fusing  point  is  higher  than  that  of  cast  iron.  At  a pusj|,j]jty 
red  heat  it  takes  fire  in  the  air,  and  alumina  is  formed;  in  oxygen 
gas  it  burns  with  intense  light  and  heat. 

It  is  not  oxidized  by  water  at  common  temperatures;  oxidation  Action  of 
commences  when  the  water  is  near  its  boiling  point,  but  even  after  water, 
continued  boiling  it  is  very  slight 

916.  Sesquioxide  of  Aluminium.  2Al-|-30,  Al,  or  A1203,  27.4  Alumina. 

2 eq.  alum.  — |—  24  3 eq.  oxy.  = 51.4equiv.  This  is  one  of  the  most 
abundant  earths  in  nature,  being  a constituent  of  many  rocks,  the 
different  kinds  of  clay,  and  of  some  of  the  hardest  gems,  as  the  ruby 

and  sapphire. 

917.  Alumina  may  be  obtained  by  dissolving  purified  alumt  in  four  or  five  Obtained, 
times  its  weight  of  boiling  water,  adding  a slight  excess  of  carbonate  of  potassa, 

and  after  digesting  for  a few  minutes,  the  bulky  hydrate  of  alumina  may  be  col- 
lected on  a filter  and  well  washed  with  hot  water.  If  an  excess  of  alkali  is  not 
employed  the  precipitate  will  retain  some  sulphuric  acid.§ 

918.  Alumina  is  destitute  of  taste  and  smell;  moistened  with  properties, 
water,  it  forms  a cohesive  and  ductile  mass,  susceptible  of  being 
kneaded  into  a regular  form.  It  is  not  soluble  in  water  ; but  retains 

a considerable  quantity,  and  is,  indeed,  a hydrate,  containing  when 
dried  at  the  temperature  of  the  atmosphere,  almost  half  its  weight  of 


*For  other  compounds  see  Turner’s  Chem.  + Edin.  Jour,  of  Sci.  No.  xvii.  178. 

t This  salt,  as  purchased  in  the  shops,  is  frequently  contaminated  with  peroxide  of 
iron,  and  consequently  unfit  for  many  chemical  purposes  ; but  it  may  be  separated  from 
this  impurity  by  repeated  crystallization.  Its  absence  is  proved  by  the  alum  being 
soluble  without  residue  in  a solution  of  pure  potassa  ; whereas  when  peroxide  of  iron 
is  present,  it  is  either  left  undissolved  in  the  first  instance,  or  deposited  after  a few 

hours  in  yellowish-brown  flocks. 

§ But  the  alumina,  as  thus  prepared,  is  not  yet  quite  pure;  for  it  retains  some  of  the 
alkali  with  such  force,  that  it  cannot  be  separated  by  the  action  of  water.  For  this 


248 


Metals — Glucinium. 


Chap.  IV. 


Effect  of 
heat. 


Recognis- 

ed. 


Sesqui- 

chloride. 


Wohler’s 

process. 


Properties. 


Glucinium. 


water.  Even  after  ignition,  alumina  has  such  an  affinity  for  moist- 
ure, that  it  can  hardly  be  placed  on  the  scale  without  acquiring 
weight.*  It  is  dissolved  by  the  liquid  fixed  alkalies,  and  is  precipi- 
tated by  acids  unchanged.  In  ammonia  it  is  very  sparingly  soluble. 

919.  Alumina  has  the  property  of  shrinking  considerably  in  bulk, 
when  exposed  to  heat.  On  this  property  was  founded  the  pyrometer 
of  Wedgwood,  designed  to  measure  high  degrees  of  heat  by  the 
amount  of  the  contraction  of  regularly  shaped  pieces  of  China  clay. 

920.  Alumina  is  easily  recognised  by  the  following  characters. 
1.  It  is  separated  from  acids,  as  a hydrate,  by  all  the  alkaline  carbo- 
nates, and  by  pure  ammonia.  2.  It  is  precipitated  by  pure  potassa 
or  soda,  but  the  precipitate  is  completely  redissolved  by  an  excess  of 
the  alkali. 

921.  Sesquichloride  of  Aluminium , 2 Al— )— 3C1  or  AP  Cl3,  27.4  2 
eq.  alumin.  -{-  106.26  3 eq.  chlor.  = 133.66  equiv.,  was  obtained 
by  Oersted,  by  transmitting  dry  chlorine  gas  over  a mixture  of  alu- 
mina and  charcoal  heated  to  redness.  It  was  afterwards  prepared 
by  Wohler  as  follows. 

922.  He  precipitated  aluminous  earth  from  a hot  solution  of  alum  by  means 
of  potassa,  and  mixed  the  hydrate,  when  dry,  with  pulverized  charcoal,  sugar, 
and  oil,  so  as  to  form  a thick  paste,  which  was  heated  in  a covered  crucible  until 
all  the  oiganic  matter  was  destroyed.  By  this  means  the  alumina  was  brought 
into  a state  of  intimate  mixture  with  finely  divided  charcoal,  and  while  yet  hot, 
was  introduced  into  a tube  of  porcelain,  fixed  in  a convenient  furnace.  After 
expelling  atmospheric  air  from  the  interior  of  the  apparatus  by  a current  of  dry 
chlorine  gas,  the  tube  was  brought  to  a red  heat.  The  formation  of  sesquichlo- 
ride of  aluminium  then  commenced,  and  continued,  with  disengagement  of  car- 
bonic oxide  gas,  during  an  hour  and  a half,  when  the  tube  became  impervious 
from  sublimed  sesquichloride  collected  within  it.  The  process  was  then  ne- 
cessarily discontinued. 

923.  It  is  of  a pale  greenish  colour,  translucent,  lamellated,  and 
like  talc.  Exposed  to  air,  it  emits  fumes  having  an  odour  like  hy- 
drochloric acid,  and  deliquesces.  It  dissolves  in  water  with  a hiss- 
ing noise  and  much  heat.  It  is  volatile  a little  above  212°  and  fu- 
ses.t 

Glucinium. 

St/mb.  G.  Equiv.  26.5. 

924.  This  is  the  metallic  base  of  the  earth  glucina,  and  was  obtained 
in  1S2S  by  Wohler,  by  the  action  of  potassium  on  the  chloride, 
as  in  the  case  of  the  last  described  metal ; it  appeared  as  a gray 
powder  but  acquired  a metallic  lustre  by  burnishing,  and  was 
easily  oxidized. $ 


reason  the  precipitate  must  be  re-dissolved  in  dilute  hydrochloric  acid,  and  thrown 
down  by  means  of  pure  ammonia,  or  its  carbonate.  This  precipitate,  after  being  well 
washed  and  exposed  to  a white  heal,  yields  pure  anhydrous  alumina.  -Ammonia  can- 
not be  employed  for  precipitating  aluminous  earth  directly  from  alum,  because  sul- 
phate of  alumina  is  not  completely  decomposed  by  this  alkali.  (Berzelius.)  An  easier  • 
process,  proposed  by  Gay-Lussac,  is  to  expose  sulphate  of  alumina  and  ammonia  to  a 
strong  heat,  so  as  to  expel  the  ammonia  and  sulphuric  acid. 

For  other  processes  see  Ure’s  Diet.  3.  147. 

* Berzelius  found,  that  100  parts  of  alumina,  after  being  ignited  gained  15J  from  a 
dry  atmosphere,  and  33  from  a humid  one.  For  a full  saturation,  100  grains  of  alu- 
mina, he  ascertained,  require  54  of  water.*  It  does  not  affect  vegetable  colours. 

t Aluminium  combines  with  sulphur,  phosphorus  and  selenium,  for  which  see  Tur- 
ner, 299.  t Phil.  Mag.  and  Annals,  v.  392. 

* Jinn,  dt  CAtm,  et  Phys.  v.  101. 


Yttrium. 


249 


925.  Sesquioxide  of  Glucinium  or  Glucina , 2G4-30,  G,  or  G203,  

— Sesquiox- 

was  discovered  by  Vauquelin  in  the  beryl,  emerald  and  euclase.  ide  or  glu- 

The  process  proposed  by  Berthier  for  obtaining  it,  is  to  mix  the  beryl  in  fine  Clna’ 
powder  with  its  own  weight  of  marble  and  expose  the  mixture  in  a crucible  to  a Process  for, 
strong  heat.  A glass  is  obtained  which  when  in  fine  powder  is  attacked  by  hy- 
drochloric or  sulphuric  acid.  The  mass  is  then  dissolved  in  dilute  hydrochloric 
acid,  and  the  solution  evaporated  to  perfect  dryness  ; by  which  means  the  silicic 
acid  is  rendered  quite  insoluble.  The  alumina  and  glucina  are  then  redissolved 
in  water  acidulated  with  hydrochloric  acid,  and  thrown  down  together  by  pure 
ammonia.  The  precipitate,  after  being  well  washed,  is  macerated  with  a large 
excess  of  carbonate  of  ammonia,  by  which  glucina  is  dissolved ; and  on  boiling 
the  filtered  liquid,  carbonate  of  glucina  subsides.  By  means  of  a red  heat  its 
carbonic  acid  is  entirely  expelled. 

926.  Glucina  is  a white  powder,  which  has  neither  taste  nor  Properties, 
odour,  and  is  quite  insoluble  in  water.  Its  sp.  gr.  is  3.  Vegetable 
colours  are  not  affected  by  it.  The  salts  which  it  forms  with  acids 

have  a sweetish  taste,  a circumstance  which  distinguishes  glucina 
from  other  earths,  and  from  which  its  name  is  derived.  (From 
yXvxrjs,  sweet.) 

927.  Glucina  may  be  known  chemically  by  the  following  charac-  Distin- 
ters.  1.  Pure  potassa  or  soda  precipitates  glucina  from  its  salts,  but  guished, 
an  excess  of  the  alkali  redissolves  it.  2.  It  is  precipitated  perma- 
nently by  pure  ammonia  as  a hydrate,  and  by  fixed  alkaline  carbo- 
nates as  a carbonate  of  glucina.  3.  It  is  dissolved  completely  by  a 

cold  solution  of  carbonate  of  ammonia,  and  is  precipitated  from  it  by 
boiling.  By  means  of  this  property,  glucina  may  be  both  distin- 
guished and  separated  from  alumina.  T. 

Yttrium. 

Syrnb.  Y 

928.  Yttrium  is  the  metallic  base  of  an  earth  which  was  discov- 
ered in  the  year  1794  by  Gadolin,  in  a mineral  found  at  Ytterby  in 
Sweden,  from  which  it  received  the  name  of  yttria.  The  metal  it-  ^Urium, 
self  was  prepared  by  Wohler  in  1828,  by  a process  similar  to  that 
above  described. 

929.  Its  texture,  by  which  it  is  distinguished  from  glucinium  and  Properties, 
aluminium,  is  scaly,  its  colour  grayish  black,  and  its  lustre  perfectly 
metallic.  In  colour  and  lustre  it  is  inferior  to  aluminium,  bearing 

in  these  respects  nearly  the  same  relation  to  that  metal,  that  iron 
does  to  tin.  It  is  a brittle  metal,  while  aluminium  is  ductile.  It  is 
not  oxidized  either  in  air  or  water;  but  when  heated  to  redness,  it 
burns  with  splendour  even  in  atmospheric  air,  and  with  far  greater 
brilliancy  in  oxygen  gas.  The  product,  yttria,  is  white,  and  shows 
unequivocal  marks  of  fusion.  It  dissolves  in  sulphuric  acid,  and 
also,  though  less  readily,  in  solution  of  potassa ; but  it  is  not  attack- 
ed by  ammonia.  It  combines  with  sulphur,  selenium,  and  phospho- 
rus.^ 

930.  The  salts  of  yttria  have  in  general  a sweet  taste,  and  the  Characters 
sulphate,  as  well  as  many  of  its  salts,  has  an  amethyst  colour.  It  is  ofltssalts> 
precipitated  as  a hydrate  by  the  pure  alkalies,  and  it  is  not  redis- 
solved by  an  excess  of  the  precipitant ; but  alkaline  carbonates,  es- 


* Phil.  Mag.  and  Annals , v.  393. 

32 


250 


• Metals — Zirconium. 


Chap.  IV. 


Equivalent. 


Discovery, 


Process  for, 


Oxidation 

of, 


Thorina, 

Properties, 

Distin- 

guished- 


Zirconium, 


pecially  that  of  ammonia,  dissolve  it  in  the  cold,  though  less  freely 
than  glucina,  and  carbonate  of  yttria  is  precipitated  by  boiling.  Of 
all  the  earths  it  bears  the  closest  resemblance  to  glucina;  but  it  is 
readily  distinguished  from  it  by  the  colour  of  its  sulphate,  by  its  in- 
solubility in  pure  potassa,  and  by  yielding  a precipitate  with  ferro- 
cyanuret  of  potassium.* 

931.  The  equivalent  of  yttrium,  as  deduced  by  Berzelius,  is  32.2  ; 
and  that  of  yttria,  which  is  probably  a protoxide,  is  40.2.  T. 

Thorium. 

Symb.  Th  Equiv.  69. 6 

932.  The  earthy  substance  formerly  called  thorina , was  found  by 
Berzelius  to  be  phosphate  of  yttria;  but  in  1828  he  discovered  a 
new  earth,  so  similar  in  some  respects  to  what  was  formerly  called 
thorina,  that  he  applied  this  term  to  the  new  substance. 

933.  The  metallic  base  of  thorina  (thorium)  was  procured  by  the 
action  of  potassium  on  chloride  of  thorium,  decomposition  being  ac- 
companied with  a slight  detonation.  On  washing  the  mass,  thorium 
is  left  in  the  form  of  a heavy  metallic  powder,  of  a deep  leaden-gray 
colour ; and  when  pressed  in  an  agate  mortar,  it  acquires  metallic 
lustre  and  an  iron-gray  tint. 

934.  Thorium  is  not  oxidized  either  by  hot  or  cold  water;  but 
when  gently  heated  in  the  open  air,  it  burns  with  great  brilliancy, 
comparable  to  that  of  phosphorus  burning  in  oxygen.  The  resulting 
thorina  is  as  white  as  snow,  and  does  not  exhibit  the  least  trace  of 
fusion.  It  is  not  attacked  by  caustic  alkalies  at  a boiling  heat,  is 
scarcely  at  all  acted  on  by  nitric  acid,  and  very  slowly  by  the  sul- 
phuric; but  it  is  readily  dissolved  with  disengagement  of  hydrogen 
gas  by  hydrochloric  acid.  T. 

935.  Thorina  was  procured  from  a rare  mineral  from  Norway, 
called  thorite , of  which  it  constitutes  57.91  per  cent. 

936.  Thorina  is  a white  earthy  substance,  of  sp.  gr.  9.402  inso- 
luble in  all  the  acids  except  the  sulphuric it  dissolves  even  in  that 
with  difficulty.  It  is  precipitated  from  its  solutions  by  the  caustic 
alkalies  as  a hydrate,  and  in  this  state  absorbs  carbonic  acid  from 
the  atmosphere,  and  dissolves  readily  in  acids.  Its  exact  composi- 
tion is  not  known  ; but  its  equivalent  is  about  67.6. 

937.  Thorina  is  distinguished  from  alumina  and  glucina  by 
its  insolubility  in  pure  potassa ; from  yttria  by  forming  with  sulphate 
of  potassa  a double  salt  which  is  quite  insoluble  in  a cold  saturated 
solution  of  sulphate  of  potassa. 

Zirconium. 

Symb.  Zr  Eq.  about  33.7? 

938.  The  experiments  of  Davy  proved  zirconia  to  be  an  oxidized 
body,  and  afforded  a presumption  that  its  base,  Zirconium , is  of  a 
metallic  nature.  When  potassium  was  brought  into  contact  with 
zirconia  ignited  to  whiteness,  potassa  was  formed,  and  dark  particles 
of  a metallic  aspect  were  diffused  through  the  alkali.  The  decom- 
position of  this  earth,  however,  had  not  been  effected  in  a satisfactory 


* Berzelius. 


Manganese. 

manner  until  the  year  1824,  when  Berzelius  succeeded  in  obtaining  Sect. 
zirconium  in  an  insulated  state. 

939.  Zirconium  is  procured  by  heating  a mixture  of  potassium  with  the  dou-  How  pro- 
ble  fluoride  of  zirconia  and  potassa,  carefully  dried,  in  a tube  of  glass  or  iron,  by  cured, 
means  of  a spirit  lamp.  The  reduction  takes  place  at  a temperature  below  red- 
ness, and  without  emission  of  light.  The  mass  is  then  washed  with  boiling  wa- 
ter, and  afterwards  digested  for  some  time  in  dilute  hydrochloric  acid.  A small 
portion  of  hydrate  of  zirconia  however  still  adheres  to  the  zirconium. 

940.  Zirconium  thus  obtained,  is  in  the  form  of  a black  powder,  Properties, 
which  may  be  boiled  in  water  without  being  oxidized,  and  is  attacked 

with  difficulty  by  the  sulphuric  or  nitro-hydrochloric  acids  ; but  is 
dissolved  readily,  and  with  disengagement  of  hydrogen  by  hydro- 
fluoric acid. 

941.  Heated  in  the  open  air  it  takes  fire  at  a temperature  far  below  Combus- 

incandescence,  burns  brightly  and  is  converted  into  zirconia.  tion  °** 

942.  Zirconium  may  be  pressed  out  into  thin  shining  scales  of  a 
dark  gray  colour,  and  of  a lustre  which  may  be  called  metallic,  but 
its  particles  adhere  together  very  feebly.  It  is  a non-conductor  of 
electricity. 

943.  Sesquioxide  of  Zirconium , or  Zirconia , 2Zr-|-30,  Zr,  or  Sesquiox- 
Zr203,  was  discovered  in  1789  by  Klaproth.  It  is  obtained  from  the  j*®  zir' 
zircon  or  jargon  of  Ceylon.  The  zircon  in  fine  powder  may  be  fused 

with  litharge  in  the  ratio  of  17  to  21,  when  a glass  is  obtained  which 
is  soluble  in  acids. 

944.  Zirconia  is  in  the  form  of  a fine  white  powder,  which,  Properties, 
when  rubbed  between  the  fingers,  has  somewhat  of  the  harsh  leel  of 

silica.  It  is  entirely  destitute  of  taste  or  smell.  Its  specific  gravity 
exceeds  4.  It  is  insoluble  in  water,  yet  appears  to  have  some  affi- 
nity for  that  fluid,  retaining  when  slowly  dried  after  precipitation, 
one  third  its  weight,  and  appearing  like  gum  arabic. 

945.  Exposed  to  a strong  heat,  zirconia  fuses,  assumes  a light  Effect  of 
gray  colour;  and  such  hardness,  on  cooling,  as  to  strike  fire  with  heat, 
steel,  and  to  scratch  even  rock  crystal.* 


Section  V.  Metals , the  Oxides  of  which  are  neither  Alkalies  nor 

Earths. 

I.  METALS  WHICH  DECOMPOSE  WATER  AT  A RED  HEAT. 

Manganese. 

Symb.  Mn  Equiv.  27.7 

946.  The  common  ore  of  manganese  is  the  black  or  peroxide, 
which  is  found  native  in  great  abundance. 

The  metal  is  obtained  by  mixing  this  oxide,  finely  powdered,  with  pitch,  process  for 
making  it  into  a ball,  and  putting  this  into  a crucible,  with  powdered  charcoal,  obtaining 
one  tenth  of  an  inch  thick  on  the  sides,  and  one  fourth  of  an  inch  deep  at  the  metallic 
bottom.  The  empty  space  is  then  to  be  filled  with  powdered  charcoal,  a cover  manganese, 
is  to  be  luted  on,  and  the  crucible  exposed,  for  one  hour,  to  the  strongest  heat 
that  can  be  raised. 

Manganese  is  a hard  brittle  metal,  of  a grayish-white  colour,  and 
granular  texture.  When  exposed  to  air  it  becomes  an  oxide.  Its 
specific  gravity  is  8.013.  It  is  not  attracted  by  the  magnet,  except 
when  contaminated  with  iron. 


* For  other  characters  see  Turner’s  Elements , 303. 


252 


JWetals — Manganese . 


Chap,  iv.  947.  It  slowly  decomposes  water  at  common  temperatures,  and 
Equivalent-  rapidly  at  a red  heat. 


Oxides  of  Manganese * 

Protoxide,  948.  Protoxide  Mn+O,  Mn,  or  MnO,  27.7  1 eq.  mang.  -f- 
8 1 eq.  oxy.  = 35.7  equiv.,  is  that  oxide  of  manganese  which  is 
a strong  salifiable  base  present  in  all  the  ordinary  salts  of  this  me- 
tal, and  which  appears  to  be  its  lowest  degree  of  oxidation. 

Process  for  ma^  ^orme(^  by  exposing  the  peroxide,  sesquioxide,  or  red  oxide  of  man- 
’ ganese  to  the  combined  agency  of  charcoal  and  a white  heat ; or  by  exposing  ei- 
ther of  the  oxides  of  manganese,  contained  in  a glass  or  iron  tube,  to  a current  of 
hydrogen  gas  at  a high  temperature.  For  this  purpose  the  red  oxide,  prepared 
from  the  nitrate  of  oxide  of  manganese,  is  the  best. 


Another, 


Properties. 


Salts. 


It  is  also  obtained  by  fusing  the  chloride  in  a platinum  crucible 
with  about  twice  its  weight  of  carbonate  of  soda  and  dissolving  the 
chloride  of  sodium  in  water. 

949.  It  is  of  a green  colour,  and,  according  to  some,  attracts  ox- 
ygen rapidly  from  the  air,  but  in  Turner’s  experiments  was  very 
permanent,  undergoing  no  change  during  nineteen  days.t  It  oxi- 
dized at  600°.  It  unites  with  acids  producing  the  same  salts  as  the 
carbonate.  If  quite  pure  it  should  dissolve  in  cold  dilute  sulphuric 
acid.t 

950.  The  salts  of  manganese  are  in  general  colourless  if  pure, 
but  often  have  a shade  of  pink  from  the  presence  of  red  oxide  or 
permanganic  acid.  The  alkalies  precipitate  the  protoxide  as  a white 
hydrate,  the  carbonates  give  a white  carbonate,  and  ferrocyanuret 
of  potassium  gives  a white  ferrocyanuret  of  manganese,  a character 
by  which  the  absence  of  iron  may  be  demonstrated.  The  white 
precipitates  become  brown  from  absorption  of  oxygen. 


Sesquiox- 

ide, 


Properties. 


Peroxide, 


951.  Sesquioxide  2Mn-|-30,  Mn,  or  Mn203,  55.4  2 eq.  mang. 
+ 24  3 eq.  oxy.  = 79.4  equiv.,  occurs  nearly  pure  in  nature, 
and  is  found  as  a hydrate  at  Ilefeld  in  the  Hartz.  It  may  be 
formed  artificially  by  exposing  peroxide  of  manganese  for  a conside- 
rable time  to  a moderate  red  heat,  and,  therefore,  is  the  chief  residue 
of  the  usual  process  for  procuring  a supply  of  oxygen  gas. 

952.  The  colour  varies  with  the  source  from  which  it  is  derived. 
That  which  is  procured  by  means  of  heat  from  the  native  peroxide 
or  hydrated  sesquioxide  has  a brown  tint;  but  when  prepared  from 
nitrate  of  oxide  of  manganese,  it  is  nearly  as  black  as  the  peroxide, 
and  the  native  sesquioxide  is  of  the  same  colour.  With  sulphuric 
and  hydrochloric  acids,  it  yields  oxygen  and  chlorine  gases.  It  is 
more  easily  attacked  than  the  peroxide  by  cold  sulphuric  acid.  With 
strong  nitric  acid,  it  yields  a soluble  protonitrate  and  the  peroxide. 

953.  Peroxide  Mn-f-20,  27.7  1 eq.  mang.  — |—  16  2 eq.  oxy. 
= 43.7  equiv.  This  is  the  well  known  ore  commonly  called 


* In  studying  metallic  oxides,  it  is  necessary,  as  remarked  by  Turner,  to  distinguish 
oxides  formed  by  the  direct  union  of  oxygen  and  a metal,  from  those  that  consist  of 
two  other  oxides  united  with  each  other,  and  which  therefore)  in  composition,  partake 
of  the  nature  of  a salt  rather  than  of  an  oxide. 

+ Phil.  Trans.  Edin.  1828,  and  Phil.  Mag.  iv. 

t For  the  method  of  preparing  pure  salts  from  common  peroxide  of  manganese,  see 
Turner’s  Elements,  6th  ed.,  p 305. 


253 


Red  Oxide  of  Manganese . 


from  its  colour  the  black  oxide.  It  generally  occurs  massive,  of  an  Sect,  v. 
earthy  appearance,  and  mixed  with  other  substances,  such  as  sili- 
ceous and  aluminous  earths,  oxide  of  iron  and  carbonate  of  lime.  It 
also  occurs  crystallized,  with  an  imperfect  metallic  lustre.  It  may  be 
made  artificially  by  exposing  the  nitrate  of  manganese  to  a com- 
mencing red  heat,  until  the  whole  of  the  nitric  acid  is  expelled. 

954.  The  peroxide  of  manganese  undergoes  no  change  on  expo- Properties, 
sure  to  the  air.  It  is  insoluble  in  water,  and  does  not  unite  either 

with  acids  or  with  alkalies.  When  boiled  with  sulphuric  acid,  it 
yields  oxygen  gas,  and  a sulphate  of  the  protoxide  is  formed  (365). 

With  hydrochloric  acid,  a hydrochlorate  is  generated,  and  chlorine 
is  evolved  (608).  On  exposure  to  a red  heat,  it  is  converted  with 
evolution  of  oxygen  gas,  into  the  sesquioxide  of  manganese. 

955.  The  peroxide  of  manganese  is  employed  in  the  arts,  in  the  Uses, 
manufacture  of  glass,  and  in  preparing  chlorine  for  bleaching.  In 

the  laboratory  it  is  used  for  procuring  chlorine  and  oxygen  gases, 
and  in  the  preparation  of  the  salts  of  manganese. 

956.  The  hydrated  peroxide  of  manganese  which  is  sometimes  Black  wad, 
called  black  wad , and  which  occurs  in  froth-like  coatings  on  other 
minerals,  is  remarkable  for  its  spontaneous  inflammation  with  oil. 

If  half  a pound  of  this  be  dried  before  a fire,  and  afterwards  suffered  to  cool  Spontane- 
for  about  an  hour,  and  it  be  then  loosely  mixed  or  kneaded  with  two  ounces  ofous  infiam- 
linseed  oil ; the  whole,  in  something  more  than  half  an  hour,  becomes  gradually  niation  °f* 
hot,  and  at  length  bursts  into  flame.  U.  573. 

957.  Red  oxide  Manganese.  Mn0-)-Mn203,  or  2Mn0~{-Mn02,  Red  0X1£{e> 
83.1  3 eq.  mang.  + 32  4 eq.  oxy.  ==  115.1  equiv.  The  substance 

called  red  oxide  of  manganese,  oxidum  manganoso-manganicum  of 
Arfwedson,  occurs  as  a natural  production,  and  may  be  formed  artifi- 
cially by  exposing  the  peroxide  or  sesquioxide  to  a white  heat  either 
in  close  or  open  vessels.  It  is  also  produced  by  absorption  of  oxygen 
from  the  atmosphere  when  the  protoxide  is  precipitated  from  its  salts 
by  pure  alkalies,  or  when  the  anhydrous  protoxide  or  carbonate  is 
heated  to  redness. 

958.  Fused  with  borax  or  glass  it  communicates  a beautiful  Fused,  &c. 
violet  tint,  a character  by  which  manganese  may  be  easily  detected 

before  the  blow-pipe ; and  it  is  the  cause  of  the  rich  colour  of  the 
amethyst.  By  cold  concentrated  sulphuric  acid  it  is  dissolved  in 
small  quantity.  The  liquid  has  an  amethyst  tint,  which  disappears 
when  heat  is  applied,  or  by  the  action  of  deoxidizing  substances. 

959.  It  may  be  doubted  whether  the  red  oxide  is  not  rather  a Composi- 
kind  of  salt  composed  of  two  other  oxides,  than  a direct  compound  of tion- 
manganese  and  oxygen.  From  the  ratio  of  its  elements  it  may  con- 
sist either  of 


Sesquioxide  . . 79.4  or  one  eq.  ) C Peroxide 

Protoxide  . . 35.7  or  one  eq. ) °r  < Protoxide  . 


. 43  7 or  one  eq. 
. 71.4  or  two  eq. 


115.1 

It  contains  27.586  per  cent,  of  oxygen,  and  loses 
when  converted  into  the  green  or  protoxide.^  T. 


145.1 

6.896  per  cent. 


* Varvicite.  Mn^03-f2Mn02  (probably),  110-8  4 eq.  mang.  + 56  7 eq.oxy.  = 166.8  Varvicite. 
equiv.  This  compound  is  known  only  as  a natural  production,  having  been  first  no- 
ticed a few  years  ago  by  Phillips  among  some  ores  of  manganese  found  at  Hartshill, 
in  Warwickshire.  The  locality  of  the  mineral  suggested  its  name.  Varvicite  was  at 


254 


Metals — Manganese. 


Chap  IV. 

Manganic 

acid. 


Mineral 

chameleon. 


Exp. 


Theory. 


Manganate 
oi  potassa. 


Permanga- 
nic acid. 


Wohler’s 

process. 


960.  Manganic  Acid.  Mn+30,  M,  or  MnO3,  27.7  1 eq.  mang. 
-f-  24  3 eq.  oxy.  = 51.7  equiv.  Manganese  is  capable  of  forming 
an  acid  with  oxygen.  Manganate  of  potassa  is  generated  when  hy- 
drate or  carbonate  of  potassa  is  heated  to  redness  with  peroxide  of 
manganese ; and  nitre  may  be  used  successfully,  provided  the  heat 
be  high  enough  to  decompose  the  nitrate  of  potassa.* 

961.  The  materials  absorb  oxygen  from  the  air  when  fused  in 
open  vessels ; but  manganate  of  potassa  is  equally  well  formed  in 
close  vessels,  one  portion  of  oxide  of  manganese  then  supplying  oxy- 
gen to  another.  The  product  has  been  long  known  under  the  name 
of  mineral  chameleon , from  the  property  of  its  solution  to  pass  rapidly 
through  several  shades  of  colour  : on  the  first  addition  of  cold  water, 
a green  solution  is  formed  which  soon  becomes  blue,  purple,  and 
red  ; and  ultimately  a brown  flocculent  matter,  hydrated  peroxide  of 
manganese,  subsides,  and  the  liquid  becomes  colourless.! 

Put  equal  quantities  of  this  substance  into  two  separate  glass  vessels,  and  pour 
on  the  one  hot,  and  on  the  other  cold  water.  The  hot  solution  will  have  a beau- 
tiful green  colour,  and  the  cold  one  a deep  purple.  The  same  material,  with  wa- 
ter of  different  temperatures,  assumes  various  shades  of  colour. 

The  phenomena  are  owing  to  the  formation  of  manganate  of  po- 
tassa of  a green  colour,  and  to  its  ready  conversion  into  the  red  per- 
manganate of  potassa,  the  blue  and  purple  tints  being  due  to  a mix- 
ture of  these  compounds.  Manganic  acid  itself  cannot  be  obtained 
in  an  uncombined  state,  because  it  is  then  resolved  into  the  hydrated 
peroxide  and  oxygen. 

962.  Manganate  of  potassa  is  obtained  in  crystals  by  forming  a 
concentrated  solution  of  mineral  chameleon  in  cold  water,  very  pure 
and  free  from  carbonic  acid,  allowing  it  to  subside  in  a stoppered 
bottle,  and  evaporating  the  clear  green  solution  in  vacuo  with  the 
aid  of  sulphuric  acid.  All  contact  of  paper  and  other  organic  matter 
must  be  carefully  avoided,  since  they  deoxidize  the  acid,  and  the 
process  be  conducted  in  a cool  apartment.  The  crystals  are  anhy- 
drous, and  permanent  in  the  dry  state  ; but  in  solution  the  carbonic 
acid  of  the  air  suffices  to  decompose  the  acid,  or  even  simple  dilution 
with  cold  water.  Mixed  with  a solution  of  potassa,  the  manganate 
may  be  crystallized  a second  time  in  vacuo  without  change. 

963.  Permanganic  Acid or'btWOl , 55.4  2 eq.  mang. 
— |—  56  7 eq.  oxy.  = 111.4  equiv.,  is  obtained  by  heating  a solution 
of  mineral  chameleon. 

The  process  of  Wohler  consists  in  fusing  chlorate  of  potassa  in  a platinum  cru- 
cible, and  adding  peroxide  of  manganese  in  fine  powder.  Gregory  has  improved 
this  ; he  mixes  4 parts  of  the  peroxide  with  parts  of  the  chlorate,  adds  it  to  5 
parts  of  hydrate  of  potassa  dissolved  in  a small  quantity  of  water,  evaporates  to 


first  mistaken  for  peroxide  of  manganese,  but  is  readily  distinguished  by  its  stronger 
lustre,  greater  hardness,  more  lamellated  texture,  and  by  yielding  water  freely  when 
heated  to  redness.  Itssp.  gr.  is  4.531.  When  strongly  hehted  it  is  converted  into  red 
oxide,  losing  5.725  per  cent,  of  water,  and  7.335  of  oxygen. 

* One  part  of  manganese  well  mixed  with  three  or  four  of  nitre  may  be  exposed  to  a 
bright  red  heat  for  half  an  hour  in  a crucible.  The  crucible  should  be  but  one  third 
full. 

+ These  changes,  which  are  more  rapid  by  dilution  and  with  hot  water,  have  been  suc- 
cessively elucidated  byChevillot  and  Edwards,  Forchammer  and  Mitscherlich.  An. 
de  Ch.  et  de  Ph.  viii.  and  xlix.  113,  and  An.  of  Phil.  xvi. 


255 


Perfluoride  of  Manganese. 

dryness,  and  exposes  the  fine  powder  in  a platinum  crucible  to  a low  red  heat.  Sect.  V. 
The  mass  not  fused  is  again  powdered  and  added  to  a large  quantity  of  boiling 
water ; when  this  is  clear  it  is  to  be  decanted,  rapidly  concentrated,  and  crystal- 
lized. The  crystals  are  to  be  washed  in  a little  cold  water  and  redisso'ved  in  the 
smallest  possible  quantity  of  boiling  water. 

The  acid  may  be  obtained  by  adding  to  a solution  of  permanga-  Acid  ob- 
nate  of  baryta  dilute  sulphuric  acid  to  precipitate  the  baryta.  tained, 

964.  This  acid  has  a rich  red  colour  ; contact  with  paper  or  linen  Properties, 
as  in  filtering,  particles  of  cork,  organic  particles  floating  in  the  at- 
mosphere decompose  it  rapidly;  colouring  matters  are  bleached  by 

it ; and  in  pure  water  its  decomposition  begins  at  86°,  and  is  com- 
plete at  212°.  On  these  occasions  oxygen  gas  is  abstracted  or  given 
out,  and  hydrated  peroxide  of  manganese  subsides. 

965.  The  salts  of  permanganic  acid  are  more  permanent  than  the  Its  salts, 
free  acid ; so  that  most  of  them  may  be  boiled  in  solution,  especially 

if  concentrated.  When  heated  they  give  out  oxygen  gas ; they  de- 
flagrate like  nitre,  and  detonate  powerfully  with  phosphorus. 

966.  In  constitution  this  acid  bears  a remarkable  analogy  to  per-  Composi- 

chloric  acid.^  llon' 

967.  Perchloride  of  Manganese.  2Mn-f-7Cl,  or  Mn2Cl7,  55.4  2 Perchlo- 
eq.  mang.  -|-  247.94  7 eq.  chlor.  — 303.34  equiv.  This  compound  ride> 

is  formed  by  putting  a solution  of  permanganic  into  strong  sulphuric 
acid,  and  then  adding  fused  sea-salt. 

The  best  mode  of  preparation  is  to  form  the  green  mineral  chameleon,  and  aci- 
dulate with  sulphuric  acid  : the  solution,  when  evaporated,  leaves  a residue  of 
sulphate  and  permanganate  of  potassa.  This  mixture,  treated  by  strong  sulphuric 
acid,  yields  a solution  of  permanganic  acid,  to  which  are  added  small  fragments  of 
sea-salt,  as  long  as  coloured  vapour  continues  to  be  evolved. t 

96S.  The  perchloride,  when  first  formed,  appears  as  a vapour  of  Properties, 
a copper  or  greenish  colour ; but  on  traversing  a glass  tube  cooled 
to  — 4°,  it  is  condensed  into  a greenish-brown  coloured  liquid. 

When  generated  in  a capacious  tube,  its  vapour  gradually  displaces 
the  air,  and  soon  fills  the  tube.  If  it  is  then  poured  into  a large  flask, 
the  sides  of  which  are  moist,  the  colour  of  the  vapour  changes  in- 
stantly on  coming  into  contact  with  the  moisture,  a dense  smoke  of  a 
pretty  rose  tint  appears,  and  hydrochloric  and  permanganic  acids  are 
generated. 

It  is  hence  analogous  in  composition  to  permanganic  acid,  its  ele-  Composi- 
ments  being  in  such  a ratio  that  tlon‘ 

1 eq.  perchloride  and  7 eq.  water  2 1 eq.  permang.  acid  and  7 eq.  hydrochloric  acid. 

2Mn+7Cl  7(H+0)  -g,  2Mn-+70  7(H+C1). 

969.  Perfluoride  of  Manganese.  2Mn-|-7F,  or  Mn2F7,  55.4  p . . 

2 eq.  mang.  130.76  7 eq.  oxy.  = 186.16  equiv.  This  gase-  er  U°n  e 
ous  compound!  is  formed  by  mixing  common  mineral  chamele- 
on with  half  its  weight  of  fluor  spar,  and  decomposing  the  mixture 

in  a platinum  vessel  by  fuming  sulphuric  acid.  The  fluoride  is  then 


* Protochloride  of  Manganese,  Mn-f  Cl,  or  MnCl,  27.7  1 eq.  mang.  4-35.42  1 eq. 
chlor.  ==  63,12  equiv.,  is  best  prepared  by  evaporating  a solution  of  the  chloride  to  Protochloride, 
dryness  by  a gentle  heat,  and  heating  the  residue  to  redness  in  a glass  tube,  while  a 
current  of  hydrochloric  acid  gas  is  transmitted  through  it.  The  heat  of  a spirit-lamp 
is  sufficient  for  the  purpose.  It  fuses  readily  at  a red  heat,  and  forms  a pink-coloured 
lamehated  mass  on  cooling.  It  is  deliquescent,  and  of  course  very  soluble  in  water. 

+ Edin.  Jour,  of  Sci.  viii.  179. 

t Discovered  by  Dumas  and  Wohler,  Edin.  Jour . of  Sci.  ix. 


256 


« Metals — Iron. 


Chap.  IV. 


Iron. 


Native. 


Properties. 


Combines 
■with  oxy- 
gen. 


Effect  of 
water,  at 
common 
tempera- 
tures. 

Of  steam. 


Protosulphuret. 


disengaged  in  the  form  of  a greenish-yellow  gas  or  vapour,  of  a more 
intensely  yellow  tint  than  chlorine.  When  mixed  with  atmospheric 
air,  it  instantly  acquires  a beautiful  purple-red  colour;  and  it  is 
freely  absorbed  by  water,  yielding  a solution  of  the  same  red  tint. 
It  acts  instantly  on  glass,  with  formation  of  fluosilicic  acid  gas,  a 
brown  matter  being  at  the  same  time  deposited,  which  becomes  of  a 
deep  purple-red  tint  on  the  addition  of  water.* 

Iron. 

Symb.  Fe  Equiv.  28 1 

970.  The  most  important  native  combinations  of  iron,  whence  the 
immense  supplies  for  the  arts  of  life  are  drawn,  are  the  oxides.  Iron 
is  also  found  combined  with  sulphur,  and  with  several  acids  ; it  is  so 
abundant  that  there  are  few  fossils  free  from  it.  It  is  also  found  in 
some  animal  and  vegetable  bodies,  and  in  several  mineral  waters. 

Iron  is  sometimes  found  native,!  and  is  usually  regarded  as  of 
meteoric  origin,  for  it  is  invariably  alloyed  by  a portion  of  the  metal 
nickel,  and  a similar  alloy  is  found  in  meteoric  atones.  Native  Iron 
is  flexible,  cellular,  and  often  contains  a green  substance  of  a vitreous 
appearance.  It  has  been  found  in  Africa,  in  America,  and  in  Sibe- 
ria, where  a mass  of  it  weighing  1600  lbs.  was  discovered  by  Pallas. 
The  mass  found  in  Peru,  described  by  Don  Rubin  de  Celis,  weighed 
15  tons. 

971.  Iron  is  a metal  of  a blue  white  colour,  fusible  at  a white  heat. 
Its  specific  gravity  is  7.88.  It  has  not  been  so  long  known  as  many 
of  the  other  metals  ; it  was,  however,  employed  in  the  time  of  Mo- 
ses for  cutting  instruments.  It  is  extremely  ductile,  but  cannot  be 
hammered  out  into  very  thin  leaves. 

972.  Exposed  to  heat  and  air  iron  quickly  oxidizes,  or  in  common 
language,  rusts.  If  the  temperature  of  the  metal  be  raised,  this 
change  goes  on  more  rapidly,  and  when  made  intensely  hot,  takes 
place  with  the  appearance  of  actual  combustion.  Thus  the  small 
fragments,  which  fly  from  a bar  of  iron  during  forging,  undergo  a 
vivid  combustion  in  the  atmosphere  ; and  iron  filings,  projected 
upon  the  blaze  of  a torch,  burn  with  considerable  brilliancy.  The 
oxide,  obtained  in  these  ways  is  of  a black  colour,  and  is  still  attract- 
ed by  the  magnet. 

973.  By  contact  with  water  at  the  temperature  of  the  atmosphere, 
iron  becomes  slowly  oxidized,  and  hydrogen  gas  is  evolved.  When 
the  steam  of  water  is  brought  into  contact  with  red-hot  iron,  the  iron 
is  converted  into  black  oxide  ; and  an  immense  quantity  of  hydrogen 
gas  set  at  liberty  (405).  The  iron  is  afterward  found  to  have  lost 
all  its  tenacity,  and  may  be  crumbled  down  into  a black  powder,  to 
which  the  name  o { finery  cinder  was  given  by  Priestley. 


* Protosufphuret  of  Manganese,  Mn+S,  or  MnS.  27.7  1 eq.fmang  -f  16.1  1 eq.  sulph. 
= 43.8  equiv.,  may  lie  procured  by  igniting  the  sulphate  with  one  sixth  of  its  weight  of 
charcoal  in  powder.*  It  is  also  formed  by  the  action  of  hydrosulphuric  acjd  gas  on 
the  protosulphate  at  a red  beat.t  It  occurs  native  in  Cornwall,  and  at  Nagyag  in 
Transylvania.  It  dissolves  completely  in  dilute  sulphuric  or  hydrochloric  acid,  with 
disengagement  of  very  pure  hydrosulpnuric  acid  gas. 

t Native  iron  of  terrestrial  origin  has  been  observed  at  Canaan,  Conn.,  and  in  Guil- 
ford Co.  N.  C.  J.  D.  Dana’s  System  of  Mineralogy,  1837. 

* Berthier.  t Arfwedson  in  .9nn.  of  Phil.  voi.  vii.  N.  8. 


267 


Sesquioxide  of  Iron . 

974.  When  iron  is  dissolved  in  dilated  sulphuric  acid,  the  acid  is  Sect,  v. 

not  decomposed  ; but  the  metal  is  oxidized  at  the  expense  of  the  wa-  of  sulphu- 
ter  and  hydrogen  gas  is  obtained  (378).^  ric  acid. 

The  eq.  of  iron  has  not  been  determined  with  accuracy. 

975.  Protoxide  of  Iron , Fe-(-0,  Fe,  or  FeO,  28  L eq.  iron  -(-  Protoxide, 
8 1 eq.  oxy.  = 36  equiv.  This  oxide  is  the  base  of  the  native  car- 
bonate of  iron,  and  of  the  green  vitriol  of  commerce.  It  is  doubtful 

if  it  has  ever  been  obtained  in  an  insulated  form.  Its  salts,  particu- 
larly when  in  solution,  absorb  oxygen  from  the  atmosphere  with 
such  rapidity  that  they  may  even  be  employed  in  eudiometry. 

This  protoxide  is  always  formed  with  evolution  of  hydrogen  gas 
when  metallic  iron  is  put  into  dilute  sulphuric  acid ; and  its  compo- 
sition may  be  determined  by  collecting  and  measuring  the  gas  which 
is  disengaged. 

976.  Protoxide  of  iron  i£  precipitated  from  its  salts  as  a white  hy-  Precipita- 
drate  by  pure  alkalies,  as  a white  carbonate  by  alkaline  carbonates,  ted‘ 
and  as  a white  ferrocyanuret  by  ferrocyanuret  of  potassium.  The 

two  former  precipitates  become  first  green  and  then  red,  and  the  lat- 
ter, green  and  blue  by  exposure  to  the  air.  The  solution  of  gall- 
nuts  produces  no  change  of  colour.  Hydro-sulphuric  acid  does  not 
act  if  the  protoxide  is  united  with  any  of  the  stronger  acids;  but 
alkaline  hydrosulphates  cause  a black  precipitate,  protosulphuret  of 
iron. 

977.  Sesquioxide  of  Iron.  2Fe-[-30,  Fe,  or  Fe203,  56  2 eq.  iron  Sesquiox- 
—f-  24  3 eq.  oxy.  = 80  equiv.  The  red  or  sesquioxide  is  a natural ide' 
product,  known  as  red  hcematite.  It  occurs  massive  and  fibrous.  It 

may  be  made  by  dissolving  iron  in  nitro-hydrochloric  acid,  and  add- 
ing an  alkali.  The  hydrate  of  the  red  oxide,  consists  of  80  parts 
or  one  eq.  of  the  sesquioxide,  and  18  parts  or  two  eq.  of  water. 

97S.  It  is  not  attracted  by  the  magnet.  Fused  with  vitreous  sub-  properties. 
stances,  it  communicates  to  them  a red  or  yellow  colour.  It  com- 
bines with  most  of  the  acids,  forming  salts,  the  greater  number  of 
which  are  red.  Its  presence  may  be  detected  by  very  decisive  tests, 

The  pure  alkalies,  fixed  or  volatile,  precipitate  it  as  the  hydrate. 

Alkaline  carbonates  have  a similar  effect,  peroxide  of  iron  not  form- 
ing a permanent  salt  with  carbonic  acid.  With  ferrocyanuret  of 
potassium  it  forms  Prussian  blue.  Sulphocyanuret  of  potassium 
causes  a deep  blood-red  ; and  infusion  of  gall-nuts,  a black  colour. 
Hydrosulphuric  acid  converts  the  sesquioxide  into  protoxide  of  iron, 
with  deposition  of  sulphur.  These  reagents,  and  especially  ferrocy- 
anuret and  sulphocyanuret  of  potassium,  afford  an  unerring  test  of 
the  presence  of  minute  quantities  of  sesquioxide  of  iron.  On  this 
account  it  is  customary,  in  testing  for  iron,  to  convert  it  into  the 

* The  action  of  nitric  acid  on  iron  is  attended  by  a series  of  very  remarkable  phenome-  Action  of  nitrie 
na,  which  have  been  recently  observed  by  ScliOnbein.  He  observed  that  this  acid  of  sp.  acid> 
gr.  1.35  though  capable  of  acting  with  violence  on  ordinary  iron,  was  inert  on  an  iron 
wire,  one  extremity  of  which  had  been  previously  made  red-hot.  He  found,  too,  that 
this  indifference  to  nitric  acid,  may  be  communicated,  by  mere  contact,  from  one  iron 
wire  to  another,  by  submersion  for  a few  moments  into  strong  nitric  acid,  or  by  making 
it  the  positive  electrode  of  a galvanic  current,  the  negative  electrode  having  been  pre- 
viously introduced  into  the  acid.  Under  these  circumstances  the  wire  does  not  com- 
bine with  the  oxygen  liberated.  Faraday  has  found  that  the  same  property  is  given 
to  iron  by  contact  with  platinum,  and  that  the  effect  is  not  limited  to  nitric  acid.  See 
the  original  papers  in  Phil.  Mag.  and  Aim.  ix-  53,  x.  133,  &c. 


258 


Metals — Iron. 


Chap,  iv.  sesquioxide,  an  object  which  is  easily  accomplished  by  boiling  the 
solution  with  a small  quantity  of  nitric  acid. 

979.  Black , or  Magnetic  Oxide.  Fe0+Fe203,  36  1 eq*  protox. 
iron  + 80  1 eq.  sesquiox.  iron  = 1 16  equiv.  This  substance,  the 
oxidum  ferrosoferricum  of  Berzelius,  long  supposed  to  be  protoxide 
of  iron,  contains  more  oxygen  than  the  protoxide,  and  less  than  the 
red  oxide.  It  cannot  be  regarded  as  a definite  compound  of  iron  and 
oxygen  ; but  it  is  composed  of  the  two  real  oxides.  It  occurs  native, 
frequently  crystallized  in  the  form  of  a regular  octohedron  ; and  it  is 
not  only  attracted  by  the  magnet,  but  is  itself  sometimes  magnetic. 
It  is  always  formed  when  iron  is  heated  to  redness  in  the  open 
air  ; and  is  likewise  generated  by  the  contact  of  watery  vapour  with 
iron  at  elevated  temperatures. 

990.  The  composition  of  the  product,  however,  varies  with  the 
duration  of  the  process  and  the  temperature  which  is  employed. 
Thus,  according  to  Buchholz,  Berzelius,  and  Thomson,  100  parts  of 
iron,  when  oxidized  by  steam,  unite  with  nearly  30  of  oxygen  ; 
whereas  in  a similar  experiment  performed  by  Gay-Lussac,  37.8 
parts  of  oxygen  were  absorbed. 

991.  The  nature  of  the  black  oxide  is  farther  elucidated  by  the 
action  of  acids.  On  digesting  the  black  oxide  in  sulphuric  acid,  an 
olive-coloured  solution  is  formed,  containing  two  salts,  sulphate  of 
the  sesquioxide  and  protoxide,  which  may  be  separated  from  each 
other  by  means  of  alcohol.*  The  solution  of  these  mixed  salts  gives 
green  precipitates  with  alkalies,  and  a very  deep  blue  ink  with  infu- 
sion of  gall-nuts.  The  black  oxide  of  iron  is  the  cause  of  the  dull 
green  colour  of  bottle  glass. 

yiuwui.tu  982.  Protochloride  of  Iron.  Fe+Cl,  or  FeCl,  28  1 eq.  iron  -f- 
ride,  35.42  1 eq.  chlor.  = 63.42  equiv.  This  compound  is  formed  by 
transmitting  dry  hydrochloric  acid  gas  over  iron  at  a red  heat,  when 
hydrogen  gas  is  evolved  and  the  surface  of  the  iron  is  covered  with 
a white  crystalline  protochloride  which  at  a stronger  heat  is  sub- 
limed. Also,  on  acting  with  hydrochloric  acid  on  iron,  which  is 
dissolved  with  evolution  of  hydrogen  gas,  evaporating  to  dryness, 
and  heating  to  redness  in  a tube  without  exposure  to  the  air. 

Solution.  983.  Protochloride  of  iron  dissolves  freely  in  water,  yielding  a 
pale  green  solution,  from  which  rhomboidal  prisms  of  the  same  co- 
lour are  obtained  by  evaporation.  The  crystals  contain  several 
equivalents  of  water  of  crystallization,  deliquesce  by  exposure  to  the 
air,  owing  to  the  formation  of  sesquichloride,  and  are  soluble  in  alcohol 
as  well  as  water.  The  aqueous  solution  absorbs  oxygen  from  the 
air,  and  becomes  yellow  from  the  formation  of  sesquichloride  of  iron  : 
one  portion  of  iron  takes  oxygen  from  the  air,  and  yields  its  chlorine 
to  another  portion  of  iron,  whereby  sesquichloride  and  sesquioxide  of 
iron  are  generated,  and  the  latter  falls  as  an  ochreous  sediment  com- 
bined with  some  of  the  sesquichloride. 

Sesquichlo-  984.  Sesquichloride  of  Iron,  2Fe-j-3CI,  or  Fe2CI3,  56  2 eq.  iron 
ride.  _|_  106.26  3 eq.  chlor.  = 162.26  equiv.,  is  formed  by  the  combustion 
of  iron  wire  in  dry  chlorine  gas,  and  by  transmitting  that  gas  over 
iron  moderately  heated ; when  it  is  obtained  in  small  iridescent 
plates  of  a red  colour,  which  are  volatile  at  a heat  a little  above  212% 


Black  or 
magnetic 
oxide, 


Composi- 

tion, 


Action  of 
acids  on. 


* Proust  and  Gay-Lussac. 


259 


Protosulphuret  of  bon . 

deliquesce  readily,  and  dissolve  in  water,  alcohol,  and  ether.  On  Sect,  v. 
agitating  ether  with  a strong  aqueous  solution  of  the  sesquichloride, 
the  ether  abstracts  a part  of  it,  and  acquires  a gold-yellow  colour. 

The  readiest  mode  of  obtaining  a solution  of  the  sesquichloride  is  to  process 
dissolve  sesquioxide  of  iron  in  hydrochloric  acid.  On  concentrating 
to  the  consistence  of  syrup  and  cooling,  it  separates  as  red  crystals, 
which  by  distillation  yield  at  first  water  and  hydrochloric  acid,  and 
then  anhydrous  sesquichloride  of  iron,  leaving  a compound  of  sesqui- 
oxide and  sesquichloride  of  iron  in  crystalline  laminse. 

985.  Protiodide  of  Iron.  Fe-j-I,  or  Fel,  28  1 eq.  iron  -}~  126.3  Protiodide, 
1 eq.  iod.  = 154.3  equiv.  It  exists  as  a pale  green  solution  when 

iodine  is  digested  with  water  and  iron  wire,  the  latter  being  in  ex- 
cess ; and  on  evaporating  the  solution,  without  exposure  to  the  air, 
to  dryness,  and  heating  moderately,  the  protiodide  is  fused,  and  on 
cooling  becomes  an  opaque  crystalline  mass  of  an  iron-gray  colour 
and  metallic  lustre.  It  is  deliquescent  and  very  soluble  in  water  and 
alcohol. 

986.  Its  aqueous  solution  attracts  oxygen  rapidly  from  the  air,  un-  Solution, 
dergoing  the  same  kind  of  change  as  the  protochloride:  to  preserve 

a solution  of  protiodide  as  such,  a long  piece  of  iron  wire  should  be 
kept  permanently  in  the  liquid.  This  compound  has  been  very  sue-  Use. 
cessfully  employed  in  medical  practice.* 

987.  Sulphurets  of  Iron.  These  elements  have  for  each  other  a Sulphurets, 
remarkably  strong  affinity,  and  unite  under  various  circumstances 

and  in  several  proportions.  The  two  lowest  degrees  of  sulphura- 
tion,  the  tetrasulphuret  and  disulphuret,  were  prepared  by  Arfwed- 
son  by  transmitting  a current  of  hydrogen  gas,  at  a red  heat,  over 
the  anhydrous  disulphate  of  sesquioxide  of  iron  to  procure  the  tetrasu;- 
phuret,  and  over  anhydrous  sulphate  of  protoxide  of  iron  for  the 
disulphuret.  In  both  cases  sulphurous  acid  and  water  are  evolved, 
and  the  resulting  sulphurets  are  left  as  grayish-black  powders,  sus- 
ceptible of  a metallic  lustre  by  friction.  They  both  dissolve  in  dilute 
sulphuric  acid  with  evolution  of  hydrogen  and  hydrosulphuric  acid 
gases.t 

988.  Protosulphuret  of  Iron , Fe-j-S,  or  FeS,  28  1 eq.  iron  -f-  Protosul- 
16.1  1 eq.  sulph.  ==  44.1  equiv.,  is  prepared  by  heating  thin  laminse  Phurel° 


* Sesquiodide  of  Iron,  2Fe+3l,  or  Fe2!3,  56  2 eq.  iron  + 378  9 3 eq.  iod-  = 434  9 
«quiv.,of  a yellow  or  orange  colour  according  to  the  strength  of  the  solution,  is  obtain- 
ed by  freely  exposing  a solution  of  the  protiodide  to  the  air,  or  digesting  iron  wire 
with  excess  of  iodine,  gently  evaporating  and  suhliming  the  sesquiodide.  It  is  a vola- 
tile red  compound,  deliquescent,  and  soluble  in  water  and  alcohol. 

The  bromides  of  iron  are  formed  under  similar  conditions  to  the  chlorides  and 
iodides,  and  are  very  analogous  to  them  in  their  properties. 

ProtoJLuoride  of  Iron,  28  1 eq.  iron  + 18.68  l eq.  floor.  = 46.68  is  best  pre- 
pared by  dissolving  iron  in  a solution  of  hydrofluoric  acid,  out  of  which  it  crystallizes 
as  the  acid  becomes  saturated,  in  small  white  square  tables,  which  are  sparingly  soluble 
in  water,  and  become  pale  yellow  by  the  action  of  the  air.  By  heat  they  part  with 
their  water  of  crystallization,  and  afterwards  bear  a red  heat  without  decomposition. 
Berzelius. 

Sesquifluoride  of  Iron , 2Fe+3F,  or  Fe2F3,  56  2 eq.  iron  + 56.04  3 eq.  fluor.  = 
112.04  equiv.,  is  formed  by  dissolving  sesquioxide  of  iron  in  hydrofluoric  acid  and  yields 
a colourless  solution  even  when  saturated.  By  evaporation  it  is  left  as  a crystalline 
mass  of  a pale  flesh-colour,  and  of  a mild  astringent  taste.  It  is  sparingly  soluble  in 
water. 

t Tetrasulphuret  of  Iron.  4Fe+S,  or  Fe4S,  112  4 eq.  iron  + 16.1  1 eq.  sulph.  = 
128.1  equiv. 

Disulphuret  of  Iron.  2Fe+S„  or  Fe2S,  56  2 eq.  iron  +16,1  1 eq.  sulph.  = 72.1  equiv. 


260 


Metals — Iron. 


Chap.  IV. 


Sesquisul- 

phuret. 


Bisulphu- 

ret. 


Action  of 
acids. 


Magnetic. 


Diphoiphuret. 


of  iron  to  redness  with  sulphur  in  a covered  Hessian  crucible,  and 
continuing  the  heat  until  any  excess  of  sulphur  is  expelled.  The 
iron  is  found  with  a crust  of  protosulphuret,  which  is  brittle,  of  a 
yellowish-gray  colour  and  metallic  lustre,  and  is  attracted  by  the 
magnet.  When  pure  it  is  completely  dissolved  by  dilute  sulphuric 
acid,  yielding  pure  hydrosulphuric  acid  (754).  The  protosulphuret  of 
iron  exists  in  nature  as  an  ingredient  in  variegated  copper  pyrites  ; and 
it  falls  on  mixing  hydrosulphate  of  ammonia  with  sulphate  of  pro- 
toxide of  iron  as  a black  precipitate,  which  oxidizes  rapidly  by 
absorbing  oxygen  from  the  air,  as  soon  as  the  excess  of  hydrosul- 
phate of  ammonia  is  removed  by  washing. 

989.  Sesquisulphuret  of  Iron , 2Fe-j-3S,  or  Fe2S3,  56  2 eq.  iron  -f- 
48.3  3 eq.  sulph.  = 104.3  equiv.,  is  formed  in  the  moist  way  by 
adding  sesquichloride  of  iron  drop  by  drop  to  hydrosulphate  of  am- 
monia or  sulphuret  of  potassium  in  excess,  and  falls  as  a black  preci- 
pitate, which  is  oxidized  readily  by  the  air.  In  the  dry  way  it  is 
slowly  produced  by  the  action  of  hydrosulphuric  acid  gas  on  sesqui- 
oxide  of  iron  at  a heat  not  exceeding  212°,  water  being  also  formed  ; 
and  by  the  action  of  the  same  gas  on  the  hydrated  sesquioxide  at 
common  temperatures.  This  sulphuret,  when  anhydrous,  has  a 
yellowish-gray  colour,  is  not  attracted  by  the  magnet,  and  dissolves 
in  dilute  sulphuric  or  hydrochloric  acid,  yielding  hydrosulphuric 
acid  and  a residue  of  bisulphuret  of  iron.* 

990.  Bisulphur et  of  Iron.  Fe-(-2S,  or  FeS2,  2S  1 eq.  iron  -f- 
32.2  2 eq.  sulph.  = 60.2  equiv.  This,  the  iron  pyrites  of  mineralo- 
gists, exists  abundantly  in  the  earth.  It  occurs  in  cubes  or  some 
allied  form,  has  a yellow  colour,  metallic  lustre,  a density  of  4.981, 
and  is  so  hard  that  it  strikes  fire  with  steel.  Some  varieties  have  a 
white  colour;  but  these  usually  contain  arsenic.  Others  occur  in 
rounded  nodules,  have  a radiated  structure  divergent  from  a common 
centre,  are  often  found  in  beds  of  clay  and  are  much  disposed  by  the 
influence  of  air  and  moisture  to  yield  sulphate  of  protoxide  of  iron. 

991.  Bisulphuret  of  iron  is  not  attacked  by  any  of  the  acids  ex- 
cept the  nitric,  and  its  best  solvent  is  the  nitro-hydrochloric  acid. 
Heated  in  close  vessels  it  gives  off'  nearly  half  its  sulphur,  and  is 
converted  into  magnetic  iron  pyrites. 

992.  Magnetic  Pyrites.  5FeS-|-FeS2,  60.2  1 eq.  bisulph.  of  iron 
-f-  220.5  5 eq.  protosuph.  of  iron  = 280.7  equiv.  This  is  a natural 
product,  termed  magnetic  pyrites  from  being  attracted  by  the  magnet, 
and  was  formerly  regarded  as  protosulphuret  of  iron  ; but  it  may  be 
regarded  as  a compound  of  bisulphuret  and  protosulphuret.  It  is 
formed  by  heating  the  bisulphuret  to  redness  in  close  vessels,  by 
fusing  iron  filings  with  half  their  weight  of  sulphur,  or  by  rubbing 
sulphur  upon  a rod  of  iron  heated  to  whiteness  (754).  It  yields  hy- 
drosulphuric acid  gas.t 

* Berzelius. 

+ Diphosphuret  of  Iron.  2Fe+P,  or  Fe2P,  56  2 eq.  iron  +15.7  1 eq.  phosph.  = 
71.7  equiv.  It  is  prepared  by  exposing  the  phosphate  of  protoxide  of  iron  to  a strong 
heat  iu  a covered  crucible  lined  with  charcoal,  the  excess  of  phosphorus  being  dissi- 
pated in  vapour.  It  is  a fused  granular  mass,  of  tne  colour  and  lustre  of  iron,  but  very 
brittle,  and  is  not  attacked  by  hydrochloric  acid.  It  is  sometimes  contained  in  metal- 
lic iron,  to  the  properties  of  which  it  is  very  injurious  by  rendering  it  brittle  at  com- 
mon temperatures. 

Perphos.  of  Iron.  3Fe+4P,  or  Fe3P4,  84  3 eq.  iron+62.8  l eq.  phosph. = 146.8  equiv. 


Cast  Iron . 


261 


993.  Carburets  of  Iron.  Iron  combines  with  carbon  in  various  Sect,  v. 
proportions ; and  the  varieties  of  proportion  occasion  great  differ-  Carburets, 
ences  of  properties  in  the  compounds.  On  these  varieties,  and  the 
occasional  combination  of  a small  proportion  of  oxygen,  depend  the 
qualities  of  the  different  kinds  of  iron  used  in  the  arts,  as  cast-iron, 

steel,  &c.  &c. 

994.  The  substance  termed  Graphite,  Plumbago , and  Black  lead , is  Graphite, 
a mechanical  mixture  of  charcoal  and  iron  ; the  artificial  graphite 

is  a real  carburet.  The  last  may  be  formed  by  exposing  iron  with 
excess  of  charcoal  to  a violent  and  long  continued  heat. 

The  first  is  not  an  uncommon  mineral,  though  rarely  found  of  Uses, 
sufficient  purity  for  the  manufacture  of  pencils  the  coarser  kinds 
and  the  dust,  are  melted  with  sulphur  to  form  common  carpenters’ 
pencils : crucibles  are  sometimes  made  of  it,  and  it  forms  an  ingredi- 
ent in  compositions  for  covering  cast-iron,  and  for  diminishing  fric- 
tion in  machines.  It  contains  from  4 to  10  per  cent,  of  iron. 

995.  Plumbago  burns  with  great  difficulty  : when  intensely  heat-  Effect  of 
ed  in  a Toricellian  vacuum  by  a Voltaic  battery,  Davy  found  that  its  heat, &c. 
characters  remained  wholly  unaltered,  neither  could  any  evidence  of 

its  containing  oxygen  be  derived  from  the  action  of  potassium.  But 
when  exposed  to  the  focus  of  a powerful  burning  lens  in  oxygen  gas, 
it  was  observed  that  the  gas  became  clouded,  and  that  dew  was  de- 
posited, indicating  the  presence  of  hydrogen  or  of  water.! 

996.  An  extremely  important  part  of  the  chemical  history  of  iron  varieties 
relates  to  the  varieties  of  the  metal  which  are  found  in  commerce,  of  iron, 
These  are  much  too  numerous  to  be  dwelt  upon  here ; the  principal 

of  them  are  cast  iron , wrought  iron , and  steel. 

Of  cast  iron,  there  are  two  principal  varieties,  distinguished  by  the  Cast  iron, 
terms  ivhite  and  gray.  The  first  is  very  hard  and  brittle,  and  when 
broken,  of  a radiated  texture.  Acids  act  upon  it  but  slowly,  and 
exhibit  a texture  composed  of  a congeries  of  plates,  aggregated  in  va- 
rious positions. 

Gray  or  mottled  iron  is  softer  and  less  brittle  ; it  may  be  bored  Gray  iron, 
and  turned  in  the  lathe.  When  immersed  in  dilute  hydrochloric 
acid,  it  affords  a large  quantity  of  black  insoluble  matter,  which 
Daniell  considers  as  a triple  compound  of  carbon,  iron,  and  silicon, 
and  which  has  some  very  singular  properties.  The  texture  of  the 
metal  resembles  bundles  of  minute  needles. 

Cast  iron  always  contains  impurities,  such  as  charcoal,  undecom- 
posed ore,  and  earthy  matters,  which  are  often  visible  by  mere  in- 
spection; and  sometimes  traces  of  chromium,  manganese,  sulphur, 
phosphorus  and  arsenic  are  present.  It  fuses  readily  at  2786°  F.,t 
which  is  a full  red  heat,  and  in  cooling  it  acquires  a crystalline  gra- 
nular texture. 

997.  Cast  iron  is  converted  into  wrought  iron  by  a curious  pro- 
cess, called  puddling.  The  cast  iron  is  put  into  a reverberatory  fur-  Process  of 
nace,  and  when  in  fusion  is  stirred,  so  that  every  part  may  be  ex-  puddling, 
posed  to  the  air  and  flame.  After  a time  the  mass  heaves,  emits  a 


* See  a description  of  the  mine  at  Borrowdale,  in  Bost.  Jour . Philos,  ii.  332. 

t On  the  fusion  of  plumbago  by  means  of  Hare?s  deflagrator,  see  Amer.  Jour . vi. 
344,  &c.  t Daniell. 


262 


Metals — Iron. 


Chap.  IV. 


Difference 
in  quality. 


Structure 
of  wrought 
iron. 


Steel. 


Properties. 


Temper- 

ing. 


_ blue  flame,  and  gradually  grows  tough  and  becomes  less  fusible,  and 
at  length  congeals.  In  that  state  it  is  passed  successively  between 
rollers,  by  which  a large  quantity  of  extraneous  matter  is  squeezed 
out,  and  the  bars  are  now  malleable.  They  are  cut  into  pieces, 
placed  in  parcels  in  a very  hot  reverberatory  furnace,  and  again 
hammered  and  rolled  out  into  bars.  They  are  thus  rendered  more 
tough,  flexible  and  malleable,  but  much  less  fusible. 

998.  The  difference  in  the  quality  of  the  two  kinds  of  cast  iron, 
appears  owing  to  the  mode  of  combination,  rather  than  to  a differ- 
ence in  the  proportion  of  carbon.  According  to  Karsten,  the  carbon 
of  the  white  is  combined  with  the  whole  mass  of  iron,  and  amounts 
as  a maximum  to  5.25  per  cent. ; the  gray,  on  the  contrary,  con- 
tains from  3.15  to  4.65  per  cent,  of  carbon,  of  which  about  three 
fourths  are  in  the  state  of  graphite. 

999.  A bar  of  wrought  iron,  when  its  texture  is  examined  in  the 
mode  pointed  out  by  Daniell,  presents  a fasciculated  appearance,  the 
fibres  running  in  a parallel  and  unbroken  course  throughout  its 
length.  This  structure  may  be  well  seen  by  tearing  a bar  of 
wrought  iron  asunder. 

1000.  Steel  is  commonly  prepared  by  the  process  of  cementation, 
which  consists  in  filling  a large  furnace  with  alternate  strata  of  bars 
of  the  purest  malleable  iron  and  powdered  charcoal,  closing  every 
aperture  so  as  perfectly  to  exclude  atmospheric  air,  and  keeping  the 
whole  during  several  days  at  a red  heat.  By  this  treatment  the 
iron  gradually  combines  with  from  1.3  to  1.75  per  cent,  of  carbon, 
its  texture  is  greatly  changed,  and  its  surface  is  blistered.  It  is  sub- 
sequently hammered  at  a red  heat  into  small  bars  and  beaten,  it  is 
then  called  tilted  steel;  and  this  broken  up,  heated,  welded  and 
again  drawn  out  into  bars,  forms  shear  steel.  Mackintosh  of  Glas- 
gow, has  introduced  an  elegant  process  of  forming  steel  by  exposing 
heated  iron  to  a current  of  coal  gas;  when  carburetted  hydrogen 
is  decomposed,  its  carbon  enters  into  combination  with  iron,  and  hy- 
drogen gas  is  evolved. 

1001.  In  ductility  and  malleability  it  is  far  inferior  to  iron  ; but 
exceeds  it  greatly  in  hardness,  sonorousness,  and  elasticity.  Its 
texture  is  also  more  compact,  and  it  is  susceptible  of  a higher  polish. 
It  sustains  a full  red  heat  without  fusing,  and  is,  therefore,  less  fusi- 
ble than  cast  iron  ; but  it  is  much  more  so  than  malleable  iron.  By 
fusion  it  forms  cast  steel,  which  is  more  uniform  in  composition 
and  texture,  and  possesses  a closer  grain  than  ordinary  steel. 

1002.  When  steel  is  heated  to  a cherry-red  colour,  and  then 
plunged  into  cold  water,  it  becomes  so  extremely  hard  and  brittle,  as 
to  be  unfit  for  almost  any  practical  purpose.  To  reduce  it  from  this 
extreme  hardness,  is  called  by  the  workmen  tempering , and  is  ef- 
fected by  again  heating  the  steel  to  a certain  point.  The  surface 
being  a little  brightened  exhibits,  when  heated,  various  colours 
which  constantly  change  as  the  temperature  is  increased,  and  by 
these  colours  it  has  been  customary  to  judge  of  the  temper  of  the 
steel.* 

* For  more  extended  accounts  of  iron  and  steel,  see  Braude’s  Chem.  ii.  35 — Aikin’s 
Did.  art.  Iron— Phil.  Mag.  ii.— Supplement  to  Encydop.  Brit.— Report  of  Brit. 
Assoc.  1S37— Dumas’  Trail'd  de  Chim.  iv.  599,  and  Thomson’s  Inorg.  Chem.  i.  481,496. 


Zinc—  Ch  loride . 


263 


1003.  Steel  admits  of  being  alloyed  with  several  other  metals,  and  rf«ct.  v. 
the  alloys,  as  appears  from  a recent  investigation  of  Stodart  and  Alloys. 
Faraday*  are  applicable  to  various  uses. 

Zinc * 

Symb.  Zn  Equiv.  32.3 

1004.  This  metal  is  obtained  from  carbonate  of  zinc  or  calamine  Ore, 
and  from  the  native  sulphuret  or  blende. f The  zinc  of  commerce  or 
spelter , is  generally  impure,  containing  sulphur,  lead,  arsenic,  cop- 
per, &c.  It  may  be  freed  from  these  by  distillation  at  a white  heat  Reduction 
in  an  earthern  retort,  to  which  a receiver  full  of  water  is  adapted  ; of. 

but  the  first  portions  should  be  rejected  as  liable  to  contain  arsenic 
and  cadmium. 

1005.  Zinc  is  a bluish  white  metal,  its  specific  gravity  varies  from  properties 
6.8  to  7.1,  it  is  malleable  at  300°,  but  very  brittle  when  its  tempera-  °f  zinc- 
ture  approaches  that  of  fusion,  which  is  about  773°. I It  is  some- 
what ductile,  but  its  wire  possesses  little  tenacity. 

At  a red  heat  it  takes  fire,  burns  with  a bright  flame,  and  is  con- 
verted into  a white  flocculent  substance,  formerly  called  pompholix , 
nihil  album , and  flowers  of  zinc . 

It  is  also  oxidized  by  dilute  sulphuric  or  hydrochloric  acid,  and  Oxidized, 
the  hydrogen  evolved  contains  a small  quantity  of  metallic  zinc  in 
combination.^ 

1006.  Protoxide  of  Zinc.  Zn~j-0,Zn,  or  ZnO,  32.3  1 eq.  zinc  Protoxide. 
-J-8  1 eq.  oxy.  ==  40.3  equiv.  This  is  the  only  oxide  of  zinc  which 

acts  as  a salifiable  base,  and  the  only  one  of  known  composition. 

It  is  generated  during  the  solution  of  zinc  in  dilute  sulphuric  acid, 
and  may  be  obtained  in  a dry  state  by  collecting  the  flakes  which 
rise  during  the  combustion  of  zinc,  or  by  heating  the  carbonate  to 
redness.  At  common  temperatures  it  is  white  ; but  when  heated  to 
low  redness,  it  assumes  a yellow  colour,  which  gradually  disap- 
pears on  cooling.  It  is  quite  fixed  in  the  fire.  It  is  insoluble  in 
water. 

1007.  The  protoxide  is  precipitated  from  its  solutions  as  a white 
hydrate  by  pure  potassa  or  amtnonia,  and  as  carbonate  by  carbonate 
of  ammonia,  but  is  completely  redissolved  by  an  excess  of  the  pre- 
cipitant. The  fixed  alkaline  carbonates  precipitate  it  permanently 
as  white  carbonate  of  protoxide  of  zinc. 

When  metallic  zinc  is  exposed  for  some  time  to  air  and  moisture,  Action  of 
or  is  kept  under  water,  it  acquires  a superficial  coating  of  a gray  water* 
matter,  which  Berzelius  describes  as  a sub*oxide.  It  is  probably  a 
mixture  of  metallic  zinc  and  the  protoxide. 

1008.  Chloride  of  Zinc.  Zn-f-Cl,  or  ZnCl,  32.3  1 eq.  zinc  + Chloride. 
35.42  1 eq.  chlor.  s=  67.72  equiv.  This  compound  is  formed,  with 
evolution  of  heat  and  light,  when  zinc  filings  are  introduced  into 
chlorine  gas ; and  it  is  readily  prepared  by  dissolving  zinc  in  hy- 


* Phil.  Trans.  1822,  and  Boston  Jour.  Philos,  i.  130. 
t For  the  process  see  Brande  ii.  48.  t Daniell. 

§ Zinc  may  be  obtained  in  small  fragments  for  introduction  into  a retort  in  pre- 
paring hydrogen  gas,  by  dropping  it  in  fusion  into  cold  water.  A preferable  method 
is  to  cast  it  into  bars  of  about  quarter  of  an  inch  in  diameter  and  afterwards  break 
them  into  pieces  of  about  half  an  inch  in  length.  W. 


264 


Metals — Cadmium. 


Chap.  IV. 


Sulphuret 
or  blende. 


Uses  of 
zinc. 


Cadmium, 


Separation 

of, 


Properties. 


_ drochloric  acid,  evaporating  to  dryness,  and  heating  the  residue  in 
a tube  through  which  dry  hydrochloric  acid  gas  is  transmitted.  It 
is  colourless,  fusible  at  a heat  a little  above  212°,  has  a soft  consis- 
tence at  common  temperatures,  hence  called  butter  of  zinc , sublimes 
at  a red  heat,  and  deliquesces  in  the  air. 

1009.  Sulphuret  of  Zinc.  Zn-J-S,  or  ZnS,  32.3  1 eq.  zinc  -f- 
16.1  1 eq.  sulph.  = 49.4  equiv.  This  compound  is  well  known  to 
mineralogists  under  the  name  of  zinc  blende , and  occurs  in  dode- 
cahedral crystals  or  some  allied  form.  Its  structure  is  lamellated, 
lustre  adamantine,  and  colour  variable,  being  sometimes  yellow,  red, 
brown,  or  black.  It  may  be  formed  artificially  by  igniting,  in  a 
closed  crucible,  a mixture  of  oxide  of  zinc  and  sulphur,  or  sulphate 
of  oxide  of  zinc  and  charcoal,  or  by  drying  the  hydrated  sulphuret 
of  zinc.  Zinc  combines  also  with  Iodine,  Bromine  and  Fluorine. 

1010.  It  has  been  proposed  to  apply  zinc  to  the  purpose  of  culi- 
nary vessels,  pipes  for  conveying  water,  sheathing  for  ships,  &c. ; 
but  it  is  rendered  unfit  for  the  first  object,  by  the  facility  with  which 
the  weakest  acids  act  upon  it,  and  for  the  remaining  ones,  by  its  con- 
siderable though  slow  oxidation,  when  exposed  to  the  operation  of 
air  and  moisture.* 

Cadmium . 

Symb.  Cd  Equiv.  55.8 

1011.  This  metal  discovered  by  Stromeyer  in  1817,  is  contained 
in  certain  ores  of  zinc,  and  especially  in  the  black  fibrous  blende 
of  Bohemia.  It  has  been  detected  in  the  calamine  of  Derbyshire, 
and  in  the  zinc  of  commerce,!  and  in  the  sublimate  which  in  the 
process  for  obtaining  zinc,  rises  before  that  metal,  forming  what  the 
workmen  call  the  brown  blaze.%  It  was  called  cadmium  from 
xadpeia,  a term  applied  both  to  calamine  and  to  the  volatile  matters 
which  rise  from  the  furnace  in  preparing  brass. 

1012.  A very  elegant  process  for  separating  zinc  from  cadmium 
was  proposed  by  Wollaston.  The  solution  of  the  mixed  metals  is 
put  into  a platinum  capsule,  and  a piece  of  metallic  zinc  is  placed 
in  it.  If  cadmium  is  present,  it  is  reduced,  and  adheres  so  tena- 
ciously to  the  capsule,  that  it  may  be  washed  with  water  without 
danger  of  being  lost.  It  may  then  be  dissolved  either  by  nitric  or 
dilute  hydrochloric  acid.§ 

1013.  Cadmium,  in  colour  and  lustre,  has  a strong  resemblance  to 
tin,  but  is  somewhat  harder  and  more  tenacious.  It  is  very  ductile 
and  malleable.  Its  sp.  gr.  is  8.604  before  being  hammered,  and 
8.694  afterwards.  It  melts  at  about  the  same  temperature  as  tin, 
and  is  nearly  as  volatile  as  mercury.  When  heated  in  the  open 


* It  has  been  employed  in  the  U.  S.  as  a covering  for  the  roofs  of  buildings,  but  is 
in  many  situations  quite  unfit  for  that  purpose.  See  a paper  on  this  subject  by  Gale, 
in  Amer.  Jour.  vol.  xxxii.  315. 

+ Ann.  of  Philos,  xv.  272,  and  N.  S.  iii.  123. 

t Ann.  Philos,  iii.  435.  Some  portions  of  this  substance  yielded  from  12  to  20  per 
cent,  of  cadmium.  Ann.  of  Philos,  xiv.  and  xvii. 

§ For  Stromeyer’s  process  see  Turner,  p.  321. 


Tin. 


265 


air.  it  absorbs  oxygen,  and  is  converted  into  an  oxide,  and  is  readily  Sec>  y. 
oxidized  and  dissolved  by  nitric  acid,  which,  is  its  proper  solvent.* 

Tin. 

Syrnb . Sn  Equic.  58.9 

1014.  The  properties  of  tin  must  he  examined  in  the  state  ofTi°- 
grain-tin  or  block  tin  ; what  is  commonly  known  by  the  name  of 
tin,  being  nothing  more  than  iron  plates  with  a thin  covering  of  this 
metal.  Several  varieties  of  tin  are  met  with  in  commerce.! 

1015.  This  metal  has  been  kuown  from  the  remotest  ages.  It 
was  in  common  use  in  the  time  of  Moses,  and  was  obtained  at  a 
very  earh*  period  from  Spain  and  Britain  by  the  Phoenicians.! 

The  native  oxide,  found  in  Cornwall  and  some  other  counties,  is 
the  principal  ore  of  tin  ;9  the  metal  is  obtained  by  heating  it  to  red-  To  obtain 
ness  with  charcoal.  To  obtain  pure  tin  the  metal  should  be  boiled  Pare  tin- 
in  nitric  acid,  and  the  oxide  which  falls  down  reduced  by  heat  in 
coutact  with  charcoal  in  a covered  crucible.  U. 

1016.  Tin  has  a silvery  white  colour,  is  considerably  harder  than 

lead,  scarcely  at  all  sonorous,  very  malleable,  though  not  very  te-  Properties, 
nacious.  Under  the  hammer  it  is  extended  into  leaves,  called  tin- 
foil,  which  aTe  about  y&ots  an  inch  thick. Its  sp.  gr.  is  about 

7.291.  It  melts  at  442=,  and  by  exposure  to  heat  and  air  is  grad- 
ually converted  into  a gray  protoxide.**  Placed  upon  ignited  char- 
coal under  a current  of  oxygen  gas,  it  burns  very  brilliantly. 

* Oxide  of  Cadmium..  CcH-O.  Cd.  or  CdO,  55.8  1 eq.  cad.  -f  8 1 eq.  osv.  = 63.3 
equiv.  The  only  known  oxide  of  cadmium,  is  prepared  by  igniting  its  carbonate,  has 
an  orange  colour,  is  fixed  in  the  fire,  and  is  insoluble  in  water. 

; Sulphured  of  Cadmium.  Cd-rS.  or  CdS.  55.3  1 eq.  cad.  —15.1  1 eq.  sulph.  = 7i.§ 
equiv,  It  occars  in  mixture  or  combination  in  some  kinds  of  zinc  blende.  Cadmium 
combines  with  Chlorine.  Iodine  and  Fluorine. 

t For  the  discrimination  of  which  and  the  means  of  judging  of  its  purity.  Yauqueiia 
has  given  useful  instructions  in  the  77th  vol.  of  the  Ann.  de  Chim  and  an  interest- 
ing account  of  the  ores  of  tin.  and  of  the  processes  for  extracting  the  metal  in 
Cornwall,  has  been  given  by  Taylor  in  the  5th  vol.  of  the  Trans.  Geolog.  Sac. 
bond. 


i Pliny,  lib.  iv.  cap.  34.  and  xxxiv,  cap.  47. 

§ In  some  of  the  valleys  of  Cornwall,  tin  is  found  in  rounded  nodules,  of  various 
sizes,  mixed  with  pebbles  and  rounded  fragments  of  rocks.  To  separate  the  tin  from 
the  alluvial  matter,  currents  of  water  are  passed  over  it.  arid  hence  these  deposits 
have  been  called  stream  works,  and  the  tin  ore.  stream  tin.  A modification  of  stream 
tin  is  called  wood  tin.  It  usually  appears  in  small  banded  fragments  of  globular 
masses. 

!i  The  process  is  described  at  length  in  Aikin's  Diet  Art.  Tin. 


IT  The  process  of  making  tin-foil  consists  simply  in  hammering  out  a number  cf 
plates  of  the  metal,  laid  together  upon  a smooth  block  or  plate  of  iron.  The  smallest 
sheets  are  the  thinnest. 


**  A preparation  under  the  name  of  powdered  tin  is  sometimes  directed  to  be  pre- 
pared for  pharmaceutical  use,  by  shaking  the  melted  meml  in  a wooden  box  robbed 
with  chalk  on  the  inside:  tin  flings  have  also  a place  in  some  Pharmacopceiee.  and 
have  heen  used  as  a vermifuge  These  preparations  are.  however,  both  dangerous, 
the  metal  being  rendered  poisonous  in  the  former  case  by  a slight  oxidation,*  and 
often  creating  very  dangerous  irritation  when  giving  in  filings. 

The  moiree  metaUique , or  crystallized  tin  plate  as  it  is  called,  is  prepared  as  fol- 
lows. The  sheet  or  plate  of  tinned  iron  is  heated  until  a drop  of  water  allowed  to 
fall  upon  its  surface  begins  taboil  immediately:  one  of  the  si.les  is  then  washed  with 
a mixture  of  4 parts  by” measure  of  water,  l of  nitric  and  l of  hydrochloric  acid.  The 


P.'Til 


*d  tin. 


32’JL- 


* Or£la,  Trmu  css  Poisons,  T.  i.  2me  parue,  p.  IS. 

34 


266 


Metals—  Tin. 


ChapJV_  1017_  protoxide  0f  Tin_  gn+0i  gni  or  gn0i  539  J eq  tini  _|_  g 

Protoxide,  j eq.  oxy,  = 66.9  equiv.  When  protochloride  of  tin  in  solution  is 
mixed  with  an  alkaline  carbonate,  hydrated  protoxide  of  tin  falls, 
which  may  be  obtained  as  such  in  a dry  form  by  washing  with 
warm  water,  and  drying  at  a heat  not  above  196°,  with  the  least 
possible  exposure  to  the  air.  The  best  mode  of  obtaining  the  anhy- 
drous protoxide  is  by  heating  the  hydrate  to  redness  in  a tube  from 
which  air  is  excluded  by  a current  of  carbonic  acid  gas.  The  same 
oxide  is  formed  when  tin  is  kept  for  some  time  fused  in  an  open  ves- 
sel. T.  323. 

Properties,  1018.  Protoxide  of  tin  has  a sp.  gr.  of  6.666.  At  common  tem- 
peratures it  is  permanent  in  the  air,  but  if  touched  by  a red  hot 
body,  it  takes  fire  and  is  converted  into  the  binoxide.  It  is  dissolved 
by  the  sulphuric  and  hydrochloric  acids,  as  also  by  dilute  nitric 
acid  ; and  the  pure  fixed  alkalies  likewise  dissolve  it.  From  the 
alkaline  solution,  metallic  tin  is  gradually  deposited,  and  binoxide  of 
tin  remains  in  solution. 

Chafers  1019.  Its  salts  are  remarkably  prone  to  absorb  oxygen,  both  from 

o its  sa  ts.  tjje  ajr  an(j  from  comp0Un(js  which  yield  oxygen  readily.  Thus  it 
converts  sesquioxide  of  iron  into  protoxide,  and  throws  down  mer- 
cury, silver,  and  platinum  in  the  metallic  state  from  their  salts. 

Cassius°f  With  a solution  of  gold  it  causes  a purple  precipitate,  the  purple  of 
Cassius , which  appears  to  be  a compound  of  binoxide  of  tin  and  pro- 
toxide of  gold.1*  By  this  character  protoxide  of  tin  is  recognized 
with  certainty.  It  is  thrown  down  by  hydrosulphuric  acid  as  black 
protosulphuret  of  tin. 

Sesquiox*  1020.  Sesquioxide  of  Tin,  2Sn+30,  Sn,  or  Sn203,  117.8  2 eq. 

ide-  tin  -)-  24  3 eq.  oxy.  ==  141.8  equiv.,  may  be  made  by  mixing  re- 
cently precipitated  and  moist  hydrated  sesquioxide  of  iron  with  a 
solution  of  protochloride  of  tin.  Its  solution  in  hydrochloric  acid 
strikes  the  purple  of  Cassius  with  gold. 

Binoxide.  1021.  Binoxide  of  Tin , Sn-f-20,  Sn,  or  SnO2,  58.9  1 eq.  tin  -f- 
16  2 eq.  oxy.  — 74.9  equiv.,  is  most  conveniently  prepared  by  the 
action  of  nitric  acid  on  metallic  tin.  Nitric  acid,  in  its  most  concen- 
trated state,  does  not  act  easily  upon  tin  ; but  when  a small  quantity 
of  water  is  added,  violent  effervescence  takes  place  owing  to  the  evo- 
lution of  nitrous  acid  and  binoxide  of  nitrogen,  and  a white  powder, 
the  hydrated  binoxide  is  produced.  On  edulcorating  this  substance, 
and  heating  it  to  redness,  watery  vapour  is  expelled,  and  the  pure 
binoxide,  of  a straw-yellow  colour,  remains.  In  this  process  ammo- 


surface  assumes  a beautiful  crystalline  appearance,  and  by  heating  the  plate  at  par- 
ticular parts  with  the  blow-pipe,  or  exposing  different  parts  to  higher  and  lower  tem- 
peratures, a great  variety  of  figures  may  be  produced,  which  will  he  seen  on  washing 
the  plate  with  water.  The  various  colours  which  it  is  made  to  assume  are  commu- 
nicated by  giving  it  a coating  of  different  coloured  varnishes.  The  tin  plates  used 
for  this  purpose  should  have  a good  coating  of  metallic  tin,  or  the  iron  below  will  be 
exposed. 

Purple  of  Cas-  * This  compound  is  used  to  colour  glass  of  a purple  colour,  and  is  made  by  dissolv- 

,l0i-  ing  a lew  grains  of  tin  in  hydrochloric  acid,  diluting  the  solution  with  a large  quan- 

tity of  distilled  water,  as  a gallon  to  a drachm  measure  of  the  solution,  and  dropping 
into  the  diluted  liquid  20  or  30  drops  of  the  solution  of  gold  in  nitro-hydrochloric 
acid  (637)  to  each  gallon.  In  the  space  of  three  or  four  days,  a purple  precipitate  is 
obtained,  which  is  separated  by  filtration,  washed  and  dried.  Gray’s  Operative  Chem , 
720. 


Sulphurets  of  Tin , 267 

nia  is  generated,  a circumstance  which  proves  water  as  well  as  nitric  Sect,  v. 
acid  to  be  decomposed.  Binoxide  of  tin  may  likewise  be  obtained 
by  precipitation  from  a solution  of  bichloride  of  tin,  by  potassa,  am- 
monia, or  alkaline  carbonates. 

1022.  It  is  apt  to  separate  from  acids  spontaneously  as  a gelati- 
nous hydrate.  It  acts  the  part  of  a ! feeble  acid  and  forms  soluble 
compounds  with  the  alkalies  called  stannates.  When  melted  with  Stannates. 
glass  it  forms  white  enamel. 

1023.  Protochloride  of  Tin , Sn-f-Cl,  or  SnCl,  58  9 1 eq.  tin  Protochlo- 
35  42  1 eq.  chlor.  — 9432  equiv.,  is  obtained  by  transmitting  hv-  n e’ 
drochloric  acid  gas  over  tin  heated  in  a glass  tube,  and  hydrogen 

gas  is  evolved  : or  by  distilling  a mixture  of  granulated  tin,  with  an 
equal  weight  of  bichloride  of  mercury,  or  of  an  amalgam  of  tin  with 
calomel,  urging  the  heat  till  the  mercury  is  expelled.  A gray  fusi- 
ble solid  of  a resinous  lustre  is  obtained.  It  is  obtained  also  in  crys- 
tals from  a concentrated  solution  of  the  chloride. 

1024.  A solution  of  protochloride  of  tin  is  obtained  by  heating  Solution, 
granulated  tin  in  strong  hydrochloric  acid  as  long  as  hydrogen  gas 
continues  to  be  evolved.  This  solution  is  much  employed  as  a de- 
oxidizing agent. 

1025.  Bichloride  of  Tin.  Sn-f-2Cl,  or  SnCP,  58.9  1 eq.  tin  -j-  Bichloride, 
70. S4  2 eq.  chlor.  ==  129.74  equiv.  When  protochloride  of  tin  is 
heated  in  chlorine  gas,  or  on  distilling  a mixture  of  8 parts  of  granu- 
lated tin  with  24  of  bichloride  of  mercury,  a very  volatile,  colourless 

liquid  passes  over,  which  is  bichloride  of  tin.  In  an  open  vessel  it 
emits  dense  white  fumes,  caused  by  the  moisture  of  the  air,  and 
hence  it  was  formerly  called  the  fuming  liquor  of  Libavius,  who 
discovered  it.  At  248°  it  boils,  and  the  sp.  gravity  of  its  vapour  was 
found  by  Dumas  to  be  9.1997.  With  one  third  of  its  weight  of  wa- 
ter it  forms  a solid  hydrate,  and  in  a larger  quantity  of  water  dis- 
solves. 

1026.  The  solution  commonly  called  per  muriate  of  tin , is  much  Solution  or 
used  in  dyeing,  and  is  prepared  by  dissolving  tin  in  nitro-hydrochlo-  permuriate. 
ric  acid.  The  process  requires  care  ; for  if  the  action  be  very  rapid, 

as  is  sure  to  happen  if  strong  acid  be  employed  and  much  tin  added 
at  once,  the  peroxide  will  be  spontaneously  deposited  as  a bulky  hy- 
drate, and  be  subsequently  redissolved  with  great  difficulty.  But  the 
operation  will  rarely  fail  if  the  acid  is  made  with  two  measures  of 
hydrochloric  acid,  one  of  nitric  acid,  and  one  of  water,  and  if  the  tin 
is  gradually  dissolved,  one  portion  disappearing  before  another  is 
added.  The  most  certain  mode  of  preparation,  however,  is  to  pre- 
pare a solution  of  the  protochloride,  and  convert  it  into  the  bichloride 
either  by  chlorine,  or  by  gentle  heat  and  nitric  acid. 

1027.  Protosulphuret  of  Tin , Sn-j-S,  or  SnS,  58.9  1 eq.  tin  Sulphurets, 
16.1  1 eq.  sulph.  — 75  equiv.,  is  prepared  by  pouring  melted  tin  up- 
on its  own  weight  of  sulphur,  and  stirring  rapidly  with  a stick  during 

the  action;  as  some  tin  usually  escapes  the  sulphur  from  the  latter 
being  rapidly  expelled,  the  product  should  be  pulverized,  mixed  with 
its  weight  of  sulphur,  and  projected  in  successive  portions  into  a hot 
Hessian  crucible,  and  then  heated  to  redness,  it  is  a brittle  com- 
pound, of  a bluish-gray,  nearly  black  colour,  and  metallic  lustre, 
which  fuses  at  a red  heat,  and  acquires  a lamella  ted  texture  in 


268 


Metals — Cobalt. 


Chap. IV. 


Aurum  mu- 
sivum, 


Properties, 


Of  its  salts. 


Alloys. 


Cobalt, 


How  ob- 
tained pure. 


8eiqniaulphu- 

nt. 


cooling.  It  is  dissolved  by  hydrochloric  acid  with  evolution  of  hy- 
drosulpburic  acid.* 

1028.  Bisulphuret  of  Tin,  Sn-|-2S,  or  SnS2,  58.9  1 eq.  tin  -f- 
32.2  2 eq.  sulph.  = 91.1  equiv.,  ( aurum  musivum,)  is  formed  by 
heating  sulphur  with  peroxide  of  tin,  or,  by  heating  in  a matrass  a 
powdered  amalgam  of  12  parts’of  tin  and  6 of  mercury,  mixed  with  7 
parts  of  flowers  of  sulphurand6  of  hydrochlorate  of  ammonia.f  A gen- 
tle heat  is  to  be  applied  till  the  white  fumes  cease  to  appear,  when 
the  heat  is  to  be  raised  to  redness,  and  kept  so  for  some  time.  On 
cooling,  the  aurum  musivum  (or  Mosaic  Gold)  may  be  obtained 
by  breaking  the  matrass.  It  is  of  a beautiful  gold  coibur,  and  flaky 
in  its  structure. 

1029.  It  has  no  taste,  is  not  soluble  in  water,  acids  or  alkaline  so- 
lutions. It  is  used  as  a pigment  for  giving  a golden  colour  to  small 
statue  or  plaster  figures.  It  is  likewise  said  to  be  mixed  with  melted 
glass  to  imitate  lapis  lazuli. 

1030.  The  salts  of  tin  are  mostly  soluble  in  water  ; they  are  pre- 
cipitated of  an  orange  colour,  byhydriodic  acid  and  by  hydrosulphu- 
ret  of  ammonia,  provided  no  excess  of  acid  be  present. 

1031.  Tin  forms  useful  alloys  with  many  of  the  metals.  Pewter 
is  one  of  these  ; and  the  best  kind  of  it  is  entirely  free  from  lead, 
being  composed  chiefly  of  tin  with  small  proportions  of  antimony, 
copper,  and  bismuth.  An  amalgam  formed  by  gradually  adding 
three  parts  of  mercury  to  twelve  of  tin  melted  in  an  iron  ladle, 
and  stirring  the  mixture,  is  much  used  in  silvering  looking  glasses. 
With  potassium  and  sodium,  tin  forms  brittle  white  alloys.  Its  alloy 
with  manganese  is  not  known.  It  does  not  readily  combine  with 
iron,  but  tin-plate  may  be  considered  as  an  imperfect  alloy  of  those 
metals.  With  zinc  it  forms  a hard  brittle  alloy. I 

Cobalt  .§ 

Symb.  Co  Equiv.  29.5 

1032.  This  metal  occurs  combined  with  arsenic,  sulphur,  iron  and 
nickel ; and  according  to  Stromeyer  is  a constant  ingredient  in 
meteoric  iron.  It  is  chiefly  obtained  in  Saxony. 

1033.  it  may  be  obtained  from  the  znffrc  of  commerce  which  is  an  impure  ox- 
ide, and  which,  heated  with  a mixture  of  sand  and  potash,  affords  the  beautiful 
blue  glass  known,  in  powder,  as  smalt.  Dissolve  zaffre  in  hydrochloric  acid  and 
transmit  through  the  solution  a current  of  hydrosulphuric  acid  gas  until  the  arse- 
nious  acid  is  completely  separated  in  the  form  of  orpiment.  The  filtered  liquid 
is  then  boiled  with  a little  nitric  acid,  in  order  to  convert  the  protoxide  into  sesqui- 
oxide  of  iron,  and  an  excess  of  carbonate  of  potassa  is  added.  The  precipitate, 


* Sesquisidphuret  of  Tin,  2Sn-l-3S,  or  Sn-S3,  117.8  2 eq.  tin  -|-  48.3  3 eq.  sulph.  = 
166.1  equiv.,  is  formed  by  mixing  the  protosulphuret  in  fine  powder  with  a third  of  its 
weight  of  sulphur,  and  heating  the  mixture  to  low  redness  until  sulphur  ceases  to  es- 
cape. Its  colour  is  of  a deep  grayish-yellow;  it  is  reconverted  by  a strong  heat  into 
the  protosulphuret,  and  dissolves  in  hydrochloric  acid  gas,  yielding  hydrosulphuric 
acid  gas  ana  a residue  of  bisulphuret  of  tin. 

t Or  heat  two  parts  of  binoxide  of  tin,  two  of  sulphur,  and  one  of  sal  ammoniac  to  a 
low  red  heat  as  long  as  sulphurous  acid  rises. 

t On  the  alloys  of  tin,  a memoir  of  Dussaussoy  may  he  consulted  in  the  5th  vol.  of 
Ann.  de  Chim.  el  Phys. ; and  Chaudet’s  paper  in  the  same,  and  in  the  7 th  volume. 

§ Its  name  is  derived  from  the  term  Kobold , an  evil  spirit , applied  to  it  by  the  Ger- 
man miners  at  a time  when  they  were  ignorant  of  its  value,  and  considered  it  unfa- 
vourable to  the  presence  of  valuable  metals. 


269 


Chloride  of  Cobolt . 

consisting  of  sesquioxide  of  iron  and  carbonate  of  protoxide  of  cobalt,  after  being  Sect.  V. 
well  washed  with  water,  is  digested  in  a solution  of  oxalic  acid,  which  dissolves 
the  oxide  of  iron  and  leaves  the  oj^de  of  cobalt  in  the  form  of  an  insoluble  oxa- 
late.* On  heating  this  oxalate  in  a’ retort  from  which  atmospheric  air  is  excluded, 
a large  quantity  of  carbonic  acid  is  evolved,  and  a black  powder,  metallic  cobalt, 
is  left.t 

The  pure  metal  is  easily  procured  also  by  passing  a current  of  dry 
hydrogen  gas  over  oxide  of  cobalt  heated  to  redness  in  a tube  of  por- 
celain. In  this  state  it  is  porous,  and  if  formed  at  a low  tempera- 
ture it  inflames  spontaneously. 

1034.  Cobalt  is  a brittle  metal,  of  a reddish-gray  colour,  and  weak  Properties, 
metallic  lustre.  Its  density,  according  to  Turner,  is  7.834. 

It  fuses  at  a heat  rather  lower  than  iron,  and  when  slowly  cooled  it 
crystallizes.  It  has  usually  been  considered  to  be  attracted  by  the 
magnet,  but  the  pure  metal  is  not  so.$ 

1035.  By  exposure  to  the  atmosphere  cobalt  is  tarnished,  but  not 
oxidized  to  any  extent.  In  an  intense  heat  it  burns  with  a red  flame ; 
but,  if  pure,  it  is  not  easily  oxidized  by  a moderate  temperature.  It 
is  oxidized  by  nitric  acid,  and  decomposes  water  at  a red  heat. 

1036.  Protoxide  of  Cobalt.  Co-j-O,  Co,  or  CoO,  29.5  1 eq.  cob.  Protoxide, 
-j-  8 1 eq.  oxy.  ==  37.5  equiv.  This  oxide  is  of  an  ash-gray 
colour,  and  is  the  basis  of  the  salts  of  cobalt,  most  of  which  are  of  a 

pink  hue.  When  heated  to  redness  in  open  vessels  it  absorbs  oxygen, 
and  is  converted  into  the  sesquioxide.  It  may  be  prepared  by  de- 
composing carbonate  of  the  protoxide  by  heat  in  a vessel  from  which 
atmospheric  air  is  excluded.  It  is  recognised  by  giving  a blue  tint 
to  borax  when  melted  with  it ; and  is  employed  in  the  arts  in  the 
form  of  smalt,  for  communicating  a similar  colour  to  glass,  earthen- 
ware, and  porcelain. 

1037.  Protoxide  of  cobalt  is  precipitated  from  its  salts  by  pure  Precipita- 
potassa  as  a blue  hydrate.  Pure  ammonia  likewise  causes  a blue  ted’ 
precipitate,  which  is  redissolved  by  the  alkali  if  in  excess.  It  is 
thrown  down  as  a pale  pink  carbonate  by  carbonate  of  potassa,  soda, 

or  ammonia;  but  an  excess  of  the  last  redissolves  it  with  facility. 
Hydrosulphuric  acid  produces  no  change,  unless  the  solution  is  quite 
neutral,  or  the  oxide  is  combined  with  a weak  acid.  Alkaline  hy- 
drosulphates precipitate  it  as  a black  protosulphuret.§ 

1038.  Chloride  of  Cobalt . Co+Cl,  or  CoCl,  29.5  1 eq.  cob.  + Chloride. 
35.42  1 eq.  chlor.  = 64.92.  equiv.  It  is  obtained  in  solution  on  dis- 
solving metallic  cobalt,  its  protoxide,  or  either  of  the  other  oxides  in 
hydrochloric  acid,  with  evolution  of  hydrogen  gas  with  the  first  and 

of  chlorine  with  the  latter.  It  yields  a pink-coloured  solution,  and 
by  evaporation  small  crystals  of  the  same  colour  containing  water  of 
crystallization.  When  deprived  of  water  its  colour  is  blue,  a cha- 
racter on  which  is  founded  its  use  as  a sympathetic  .ink  : when  let- 
ters are  written  with  a dilute  solution  of  the  chloride,  the  colour  is  so 
pale  that  it  is  invisible  in  the  cold ; but  on  heating  gently,  the  letters 


* Laugier.  t Thomson  in  Ann- of  Philos.,  N.  S.  i.  + Faraday. 

§ When  a salt  of  cobalt  is  treated  with  pure  ammonia  in  close  vessels,  part  of  the  co- 
balt is  dissolved,  and  part  subsides  in  form  of  a blue  powder.  On  admitting  atmos- 
pheric air,  this  substance  passes  to  a higher  state  of  oxidation,  and  is  gradually 
dissolved.  If  nitrate  of  cobalt  is  used,  a double  salt  may  be  obtained  in  crystals, 
which  L-  Gmelin  believes  to  consist  of  nitrate  and  ccbaltate  of  ammonia.  The  exist- 
ence of  this  acid,  hb'WteV'er,  has  not  ytet  been  established. 


270 


Metals — Nickel. 


Chap.  IV. 


Alloys. 


Ores, 


Reduced. 


Properties. 


Sympathetic 

ink. 


Wollaston'* 
proce**  for  de- 
tecting nickel. 


appear  of  a blue  colour,  and  disappear  as  soon  as  the  chloride  has 
recovered  its  moisture  from  the  atmosphere.  When  iron  or  nickel  is 
present,  the  dry  chloride  of  cobalt  is  green  instead  of  blue.* * * § 

1039.  The  alloys  of  cobalt  are  unimportant.  The  chief  use  of 
this  metal  is  in  the  state  of  oxide  as  a colouring  material  for  porce- 
lain, earthenware,  and  glass ; it  is  principally  imported  from  Ger- 
many in  the  state  of  zaffre  and  smalt , or  azure.  Smalt  and  azure 
are  made  by  fusing  zaffre  with  glass  or  by  calcining  a mixture  of 
equal  parts  of  roasted  cobalt  ore,  common  potash,  and  ground  flints. 
A blue  glass  is  formed  which,  while  hot,  is  dropped  into  water,  and 
afterwards  reduced  to  a very  fine  powder. 

Nickel. 

Symb.  Ni  Equiv.  29.5 

1040.  Nickel  is  found  native,  and  is  a constituent  of  meteoric  iron.t 
It  occurs  likewise  in  the  copper-coloured  mineral  of  Westphalia, 
termed  copper-nickel , a native  arseniuret  of  nickel,  which  in  addition 
to  its  chief  constituents,  contains  sulphur,  iron,  cobalt  and  copper. 
The  combinations  of  nickel  may  be  prepared  from  its  ore,  or  from  the 
artificial  arseniuret  called  speiss.X 

The  metal  may  be  procured  by  heating  the  oxalate  in  close  ves- 
sels, or  by  the  combined  action  of  heat  and  charcoal,  or  hydrogen, 
on  protoxide  of  nickel. $ 

1041.  Crystals  of  nitrate  of  nickel,  when  placed  in  a cavity  scoop- 
ed out  of  a piece  of  charcoal,  and  exposed  to  the  oxy-hydrogen 
blow-pipe,  afford  a bead  of  metallic  nickel.  This,  however,  is  a 
process  obviously  adapted  to  yield  only  very  minute  quantities  of 
nickel. 

1042.  Nickel  is  of  a white  colour  between  that  of  tin  and  silver, 
with  a strong  lustre,  and  is  ductile  and  malleable.  It  is  attracted  by 


* This  solution  has  been  termed  Hellot's  sympathetic  ink.  It  may  be  prepared  as 
follows  : One  part  of  cohalt,  or,  still  better,  of  zaffre,  may  be  digested  in  a sand  heat, 

for  some  hours,  with  four  parts  of  nitric  acid.  To  the  solution,  add  one  part  of  sea- 
salt;  and  dilute  with  four  parts  of  water.  Characters  written  with  this  solution  are 
illegible  when  cold  ; but  when  a gentle  heat  is  applied,  they  assume  a beautiful  blue 
or  green  colour.  This  experiment  is  reudered  more  amusing  by  drawing  the  trunk 
and  branches  of  a tree  in  the  ordinary  manner;  and  tracing  the  leaves  with  the  solu- 
tion. The  tree  appears  leafless,  till  the  paper  is  heated,  when  it  suddenly  becomes 
covered  with  heautilul  foliage.  The  addition  of  a little  nitrate  o(  copper  to 
the  solution  forms  a sympathetic  ink,  which  by  heat  gives  a rich  greenish  yellow  co- 
lour. When  a small  quantity  of  hydrochlorate  of  soda,  of  magnesia,  or  of  lime,  is 
added  to  the  ink,  its  traces  disappear  very  speedily  on  removal  from  the  fire.  U.  346. 

t For  an  account  of  meteoric  stones,  masses  of  iron,  &c.  which  have  fallen  from  the 
heavens,  from  the  earliest  period  down  to  1 S 1 9,  see  Edln.  Philos  Jour.  vol.  i.  p.  221. 
See  also  Cleaveland’s  Mineralogy , p.  773,  and  Braude's  Chem.  ii.  149. 

t For  details  see  Thomson’s  Chemistry  of  Inorganic  Bodies , ii  526,  &c.,  and  Tur- 
ner, 329. 

§ For  other  processes  see  Thomson,  ii.,  Henry,  ii.  169,  Quart.  Jour.  xliv.  396,  and 
N.  S.  iii.  209. 

To  detect  the  presence  of  nickel  in  iron,  Wollaston  recommends  that  a small  por- 
tion, which  need  not  exceed  .01  of  a grain,  should  be  filed  from  the  sample,  and  dis- 
solved in  a drop  of  nitric  acid  ; evaporate  this  to  dryness,  and  add  a drop  or  two  of 
liquid  ammonia,  whicn,  when  gently  warmed,  will  dissolve  any  oxide  of  nickel  that 
may  he  present.  The  transparent  part  of  the  fluid  is  then  to  be  conducted  by  the  end 
of  a glass  rod  to  a small  distance  from  the  precipitated  oxide  of  iron,  and  mixed  with 
a drop  of  ferrocyanate  of  poiassa,  which,  if  nickel  be  present,  will  cause  an  immedi- 
ate milkiness,  not  discernible  in  a solution  of  common  iron,  formed  and  treated  in  the 
same  way.  B.  ii.  148 


Arsenic. 


271 


the  magnet,  and  may  like  iron  be  rendered  magnetic,  but  loses  this  Sect,  vi. 
power  at  630°.#  Its  sp.  gr.  is  about  8.279.  It  is  very  infusible,  Fusibility, 
suffers  no  change  by  exposure,  but  at  a red  heat  absorbs  oxygen,  and 
decomposes  water.  It  is  oxidized  by  nitric  acid.  Its  eq.  is  esti- 
mated at  29.5. 

1043.  Protoxide  of  Nickel.  Ni-f-O,  Ni,  or  NiO,  29.5  1 eq.  nick.  Protoxide. 
+ 8 1 eq.  oxy.  = 37.5  equiv.  This  oxide  may  be  formed  by 
heating  the  carbonate,  oxalate,  or  nitrate  to  redness  in  an  open  ves- 
sel, and  is  then  of  an  ash-gray  colour;  but  after  exposure  to  a white 
heat,  its  colour  is  a dull  olive-green.  It  is  not  reducible  by  heat 
unaided  by  combustibles.  It  is  not  attracted  by  the  magnet.  It  is  a 
strong  alkaline  base,  and  nearly  all  its  salts  have  a green  tint.  It  is 
precipitated  as  a hydrate  of  a pale-green  colour  by  the  pure  alkalies, 
but  is  redissolved  by  ammonia  in  excess  ; as  a pale-green  carbonate 
by  alkaline  carbonates,  but  is  dissolved  by  an  excess  of  carbonate  of 
ammonia;  and  as  a black  sulphuret  by  alkaline  hydrosulphates. 
Hydrosulphuric  acid  occasions  no  precipitate,  unless  the  solution  is 
quite  neutral,  or  the  oxide  combined  with  a weak  acid.t 


Section  VI.  Metals  which  do  not  Decompose  Water  at  any  Tem - 

perature , and  the  Oxides  of  which  are  not  reduced  to  the  Metallic 

State  by  the  sole  action  of  Heat. 

1044.  Arsenic.  As,  37.7  eq.  Metallic  arsenic  occurs  native,  but  Arsenic 
more  commonly  in  combination  with  other  metals.  The  substance 
known  in  the  shops  by  the  name  arsenic,  is  an  oxide,  from  which  the 
metal  may  be  obtained  by  mixing  it  wTith  half  its  weight  of  black 
flux, I and  introducing  the  mixture  into  a Florence  flask,  placed  in 
a sand  bath  gradually  raised  to  a red  heat;  a brilliant  metallic 
sublimate  of  pure  arsenic  collects  in  the  upper  part  of  the  flask. 

Or  mix  it  with  about  twice  its  weight  of  charcoal,  both  perfectly  dry,  and  ex-  Obtained, 
pose  the  mixture  to  heat  in  a crucible,  luting  another  over  it  in  an  inverted  posi- 
tion to  collect  the  product. § 

* Faraday. 

t Sesquioxide  of  Nickel , 2Ni+30,  Ni,  or  Ni203,  59  2 eq.  nick,  -f  24  3 eq.  oxy.  = 

83  equiv.  , has  a black  colour,  and  is  formed  by  transmitting  chlorine  gas  through  wa-  Sestiul0xlde’ 
ter  in  which  the  hydrate  of  the  protoxide  is  suspended,  does  not  unite  with  acids,  is 
decomposed  by  a red  heat,  and  with  hot  hydrochloric  acid  lorms  the  chloride  with  dis- 
engagement of  chlorine  gas. 

Chloride  of  Nickel,  Ni+Gl,  or  NiCl,  29.5  1 eq.  nick  + 35.42  I eq.  chlor.  s=  64.92 
equiv.,  is  formed  by  acting  with  hydrochloric  acid  on  metallic  nickel,  its  protoxide,  or  Chlori  ®‘ 
sesquioxide ; hydrogen  gas  being  evolved  with  ihe  former,  and  chlorine  with  the  latter. 

It  forms  an  emerald-green  solution,  and  by  evaporation  yields  crystals  of  the  same 
tint,  which  lose  water  or  deliquesce,  according  as  the  air  is  dry  or  moist. 

Protosulpkuret  of  Nickel,  Ni+S,  or  NiS,  29.5  l eq  nick. -f  16.1  1 eq.  sulph.  = 

45.6  equiv.,  is  formed  by  processes  similar  to  those  for  preparing  protosulphuret  of 
cobalt.  The  precipitated  sulphuret  is  dark  brown  or  nearly  black. 

t This  is  an  extremely  useful  compound  for  effecting  the  reduction  of  many  of  the 
metallic  oxides.  It  consists  of  charcoal  and  subcarbonate  of  potassa,  and  is  best  pre-  Black  flui> 
pared  by  deflagrating  in  a crucible  a mixture  of  one  part  of  nitre  and  two  of  powdered 
tartar.  The  mixture  remains  in  fusion  at  a red  heat,  and  thus  suffers  the  small  glo- 
bules of  reduced  metal  to  coalesce  into  a button. 

§ A small  opening  should  be  left  for  the  escape  of  gaseous  matters.  The  lower  cru- 
cible should  be  placed  in  a sand  bath  furnace,  and  the  upper  one  be  kept  as  cool  as 
possible  and  completely  out  of  the  sand  3 the  process  may  be  easily  conducted  with  a 
small  chauffer.  Care  must  be  taken  not  to  inhale  the  vapour. 


272 


Metals — -Arsenic . 


Chtlp  IV. 
Characters. 


Fly-pow- 

der. 


Arsenious 

acid, 


How  ob- 
tained, 


Properties, 


Dimor- 

phous. 


Solubility. 


Poisonous 

effects. 


1045.  Arsenic  is  of  a steel-blue  colour,  quite  brittle,  and  of  a spe- 
cifie  gravity  = 5.884.  It  readily  fuses,  and  in  close  vessels  may  be 
distilled  at  a temperature  of  360°,  which  is  lower  than  its  fusing 
point.  Its  vapour  has  a very  strong  smell,  resembling  that  of  garlic. 
Heated  in  the  air  it  easily  takes  fire,  burns  with  a blue  flame,  and 
produces  copious  white  fumes  of  oxide. 

In  general  it  speedily  tarnishes  by  exposure  to  air  and  moisture, 
acquiring  upon  its  surface  a dark  film,  which  is  extremely  superficial ; 
but  Berzelius  remarks  that  he  has  kept  some  specimens  ir^open  ves- 
sels for  years  without  loss  of  lustre,  while  others  are  oxidized  through 
their  whole  substance,  and  fall  into  powder.  The  product  of  this 
spontaneous  oxidation,  which  is  known  under  the  name  of  Jly-powder, 
is  supposed  by  Berzelius  to  be  an  oxide;  but  it  is  more  generally  re- 
garded as  a mixture  of  white  oxide  and  metallic  arsenic. 


1046.  Arsenious  Acid , 2As-|-30,  As,  or  As203,  75.4  2 eq  arsen. 
-f-  24  3 eq.  oxy.  = 99.4  equiv.,  or,  as  it  is  commonly  called,  white 
arsenic , or  white  oxide  of  arsenic , is  the  best  known,  and  most  com- 
monly occurring  compound  of  this  metal;  and  as  cases  of  poison- 
ing by  it  are  frequent,  every  person  should  be  well  acquainted  with 
its  characteristic  properties. 

1047.  Arsenious  acid  may  easily  be  procured  by  the  combustion 
of  the-  metal  ; but  as  it  is  formed  during  certain  tnetallurgic  proces- 
ses, that  mode  is  rarely,  resorted  to.  It  is  abundantly  prepared  in 
Bohemia,  from  arsenical  cobalt  ores,  which  are  roasted  in  reverbera- 
tory furnaces,  and  the  vapours  condensed  in  a long  chimney,  the 
contents  of  which,  submitted  to  a second  sublimation,  afford  the 
white  arsenic  of  commerce. 

1048.  Arsenious  acid  is  white,  semi-transparent,  brittle,  and  of  a 
vitreous  fracture.  Its  sp.  gr.  is  3.7.  Its  taste  has  been  usually  de- 
scribed as  acrid,  but  it  appears  that  this  is  incorrect.  It  excites  a 
very  faint  impression  of  sweetness  and  perhaps  of  acidity.* 

1049.  Arsenious  acid  is  dimorphous , that  is,  susceptible  of  assum- 
ing two  crystalline  forms  belonging  to  different  systems  of  crystalli- 
zation. By  slow  sublimation  in  a glass  tube,  it  is  always  obtained 
in  distinct  octohedral  crystals  of  adamantine  lustre  and  perfectly 
transparent.  Its  unusual  form  is  that  of  six-sided  scales  derived 
from  a rhombic  prism. 

1050.  According  to  Klaproth  and  Buchholz,  1000  parts  of  water 
at  60°  dissolve  2.5  of  white  arsenic,!  1000  parts  of  water  at  212°, 
dissolve  rather  more  than  77  parts,  and  about  30  parts  are  retained 
in  permanent  solution. 

Guibourt  has  lately  observed  that  the  transparent  and  opaque  va- 
rieties of  arsenic  differ  in  solubility.  He  found  that  1000  parts  of 
temperate  water  dissolve,  during  36  hours,  9.6  of  the  transparent, 
and  12  5 of  the  opaque  variety  : that  the  same  quantity  of  boiling 
water  dissolves  97  parts  of  the  transparent  variety,  retainin 


18 


* See  Cristison’s  experiments.  Edin.  Philos  Jour.  xiv.  330. 
t It  would  take  a loner  time  to  prepare  a saturated  aquwus  solution  of  white  arsenic, 
by  contact  of  the  powder  with  water,  or  even  by  agitation  ; but  by  hoi  ling  the  water 
with  the  powder  for  half  an  hour,  leaving  it  to  cool,  and  afterwards  filtering.it,  a sat- 
urated solution  will  be  at  once  obtained.  Faraday,  Chem.  Manip . 174. 


Tests  of  Arsenic. 


278 


when  cold,  but  takes  up  115  of  the  opaque  variety,  and  retains  29  Sect,  vi. 
on  cooling.  By  the  presence  of  organic  substances,  such  as  milk  or 
tea,  its  solubility  is  materially  impaired.* 

1051.  It  is  virulently  poisonous,  producing  inflammation  and  gan-  p0isonous 
grene  of  the  stomach  and  intestines;  it  also  proves  fatal  when  ap- effects, 
plied  to  a wound  ; and  as  the  local  injury  is  in  neither  case  sufficient 

to  cause  death,  it  is  probable  that  an  induced  affection  of  the  nervous 
system  and  of  the  heart  is  the  cause  of  the  mischief.  To  get  rid 
of  the  poison  by  producing  copious  vomiting  and  purging,  and  to 
pursue  the  usual  means  of  subduing  and  preventing  inflammation, 
are  the  principal  points  of  treatment  to  be  adopted  in  cases  where 
this  poison  has  been  taken.! 

1052.  As  arsenic  either  accidentally  or  intentionally  taken,  is  a Methods  of 
very  frequent  cause  of  death,  and  often  the  subject  of  judicial  in-  arsenic^ 
quiry,  it  becomes  of  importance  to  point  out  the  most  effectual  modes  ’ 

of  discovering  its  presence.  Where  arsenic  proves  fatal,  it  is  very 
seldom  found  in  the  contents  of  the  stomach  after  death,  but  is  gen- 
erally previously  voided  by  vomiting  or  by  stool ; and  we  often  can 
detect  it  in  the  matter  thrown  ofF  the  stomach,  in  the  form  of  a 
white  powder,  subsiding  in  water.  The  inflammation  of  stomach 
which  results  is  generally  a secondary  effect,  and  takes  place  equal- 
ly, whether  the  poison  be  swallowed  or  applied  to  a wound. 

1053.  Several  tests  have  been  proposed  for  detecting  minute  Tests  of. 
quantities  of  arsenic  in  the  fluids  likely  to  be  met  with  in  the  stom- 
ach, the  most  valuable  are  the  ammoniaco-nitrate  of  silver,  ammo- 
niaco-sulphate  of  copper,  hydrosulphuric  acid  and  hydrogen  gas. 

1054.  The  first  object  is  to  obtain  a concentrated  solution  of  the  Methods  of 
substances  ejected,  or,  in  case  of  death,  of  the  liquids  contained  in  Proceeding* 
the  stomach,  or  of  any  that  may  adhere  to  its  interior  surface.  This 

is  to  be  effected  by  means  of  washing  in  pure  water,  filtration,  and 
evaporation.  A solution  having  been  obtained,  the  tests  are  to  be 
applied,  it  having  been  previously  ascertained  that  they  are  perfectly 
pure,  as  also  the  vessels  in  which  the  experiments  are  to  be  made. 

1.  The  ammoniacal-nitrate  of  silver  is  made  by  dropping  into  a Ammonia- 
rather  strong  solution  of  lunar  caustic,  ammonia,  till  the  oxide  of  of  silver16 
silver  at  first  thrown  down  is  nearly  all  dissolved.  This  liquid  contains 

the  precise  quantity  of  ammonia  required  to  neutralize  the  nitric  acid 
of  the  nitrate  of  silver.  On  dropping  it  into  the  suspected  liquid,  if 
arsenic  is  presented  yellow  insoluble  arsenite  of  silver  will  be  formed. 

2.  Ammoniacal-sulphate  of  copper,  is  made  by  adding  ammonia  Ammonia- 
to  a solution  of  sulphate  of  protoxide  of  copper,  until  the  precipitate 

is  nearly  all  dissolved.  This  test  affords  a green  precipitate  with  ar- 
senious  acid,  which  has  long  been  known  as  Scheele's  green. 

3.  The  hydrosulphuric  acid  gas,  is  to  be  obtained  from  the  usual  ^^icacid 
materials  (754)  and  conducted  by  means  of  a suitable  glass  tube  into  p uncaci 
the  suspected  liquid  ; if  arsenious  acid  is  present,  the  liquid  be- 
comes yellow  and  turbid  from  the  formation  of  orpiment  or  sesqui- 
sulphuret  of  arsenic.! 

On  drying  the  sulphuret,  mixing  it  with  black  flux,  and  heating 

* Christison  on  Poisons. 

+ See  Christison’s  Experiments,  Edin.  Philos.  Jour.  xiv.  380. 

I The  apparatus  (Fig.  166),  page  200,  will  be  found  convenient. 

35 


274 


Metals — Arsenic. 


Chap,  iv.  the  mixture  contained  in  a glass  tube  to  redness  by  means  of  a spirit- 
Reduction.  lamp,  decomposition  ensues,  and  a metallic  crust  of  an  iron-gray 
colour  externally,  and  crystalline  on  its  inner  surface,  is  deposited 
on  the  cool  part  of  the  tube.  This  character  alone  is  quite  satisfac- 
tory ; but  it  is  easy  to  procure  additional  evidence,  by  reconverting 
the  metal  into  arsenious  acid,  so  as  to  obtain  it  in  the  form  of  re- 
splendent octohedral  crystals.  This  is  done  by  holding  that  part  of 
the  tube  to  which  the  arsenic  adheres  about  three-fourths  of  an  inch 
above  a very  small  spirit-lamp  flame,  so  that  the  metal  may  be 
slowly  sublimed.  As  it  rises  in  vapour  it  combines  with  oxygen, 
and  is  deposited  in  crystals  within  the  tube.  The  character  of  these 
crystals,  with  respect  to  volatility,  lustre,  transparency,  and  form,  is 
so  exceedingly  well  marked,  that  a practised  eye  may  safely  identify 
them,  though  their  weight  should  not  exceed  the  100th  part  of  a 
grain.  This  experiment  does  not  succeed  unless  the  tube  be  quite 
clean  and  dry.* 

4.  For  the  application  of  hydrogen  we  are  indebted  to  Marsh  of 
Woolwich. t Its  utility  depends  on  the  fact  that,  whenever  nascent 
hydrogen  is  brought  into  contact  with  any  compound  of  oxygen  and 
arsenic,  water  and  arseniuretted  hydrogen  are  formed.  If  the  gas 
be  inflamed  as  it  escapes  into  the  air  from  a fine  tube,  it  burns 
with  the  production  of  watery  vapour,  and  the  deposition  of  me- 
tallic arsenic.  By  holding  a piece  of  clean  glass  over  the  flame, 
its  surface  is  instantly  covered  with  a thin  coating  of  metallic  arse- 
nic ; and  if  the  flame  be  made  to  burn  in  the  centre  of  a glass  tube 
open  at  both  extremities,  so  as  to  admit  a larger  supply  of  atmos- 
pheric oxygen,  it  is  covered  in  half  a minute  with  arsenious  acid. 


Marsh’s 

Erocess  by 
ydrogen 
gas. 


Liebig’s 

improve- 

ment. 


The  hydrogen  is  obtained  by  introducing  a 
portion  of  the  suspected  liquid  into  a tube  about 
thirteen  inches  in  length  and  three  fourths  of 
an  inch  internal  diameter,  or  the  glass  bucket  c, 
in  which  is  a small  piece  of  pure  zinc  b,  sulphuric 
acid  is  added  and  the  gas  passes  out  through 
the  jet  a,  while  the  stop-cock  is  open.  When 
it  is  closed  the  gas  accumulates  in  the  upper 
part  of  the  short  leg;  on  opening  the  stop- 
cock, the  liquor  descends  from  the  longer  leg 
and  drives  out  the  gas. 

When  large  quantities  of  the  suspected  liquid  can 
be  obtained,  the  apparatus  (Fig.  180)  is  employed  ; 
see  379. 

Liebig  recommends  that  a fragment  of  porce- 

as 
better 


Fig.  179. 


181. 


be  held  in  the  flame  instead  of  the  glass, 


lain 

a very  thin  film  of  metallic  arsenic 
seen  on  the  white  opaque  ground  of  the  former. 
To  avoid  the  deposition  of  other  metals,  that 
may  be  carried  up  by  the  hydrogen,  he  recom- 
mends that  the  gas  be  transmitted  through  a 
fine  tube  of  difficultly  fusible  glass,  instead  of 


<®Bp 


* A tube  of  the  annexed  form  (Fig.  181,)  has  been  recommended  by  Berzelius, 
it  should  be  perfectly  dry,  and  the  mixture  introduced  by  means  of  a small 
funnel  descending  within  the  ball,  through  which  the  mixture  may  be  passed 
without  soiling  the  tube, 
t Edin.  Philos.  Jour.  Oct.  1836,  and  Trans ■ Soc.  Arts,  Li. 


0 


275 


Eesquichloride  of  Arsenic . 

burning  it  at  the  jet  ; on  bringing,  a part  of  the  glass  to  a red  heat 
by  a spirit-lamp,  the  arseniuretted  hydrogen  is  decomposed  as  it 
passes,  and  the  metallic  arsenic  is  deposited  just  beyond  the  heated 
part  of  the  glass,  while  other  metals  are  deposited  in  the  hot  parts 
themselves.^ 

1055.  The  extreme  delicacy  of  this  method  of  testing  for  arsenic 
has  been  fully  confirmed,  but  it  also  has  been  ascertained  that  it  is 
not  the  only  one  to  be  relied  upon.  Other  metals  may  be  present, 
as  antimony,  which  has  been  found  to  form  a gaseous  compound, 
and  to  give  results  that  resemble  those  with  arsenic.  By  decom- 
posing the  gases  while  passing  through  a fine  tube,  as  proposed  by 
Liebig,  and  obtaining  the  metals,  they  can  readily  be  distinguished.! 

1056.  Arsenic  Acid.  2AS+50,  As,  or  As203,  75.4  2 eq.  arsen. 
4"  40  5 eq.  oxy.  = 115.4  equiv.  This  compound  is  made  by  dis- 
solving arsenious  acid  in  concentrated  nitric,  mixed  with  a little  hy- 
drochloric acid,  distilling  in  glass  till  it  acquires  the  consistence  of 
syrup,  and  then  exposing  it  in  a platinum  crucible  for  some  time  to 
a heat  somewhat  short  of  low  redness  to  expel  the  nitric  acid.  The 
acid  thus  prepared  has  a sour  metallic  taste,  reddens  vegetable  blue 
colours,  and  with  alkalies  forms  neutral  salts,  which  are  termed 
arseniates.  It  is  much,  more  soluble  in  water  than  arsenious  acid. 
It  is  an  active  poison. 

1057.  Arsenic  acid  is  decomposed  by  hydrosulphuric  acid  gas, 
and  yields  a sulphuret  of  arsenic  very  like  orpiment  in  colour,  but 
containing  a greater  proportional  quantity  of  sulphur.  The  soluble 
arseniates,  when  mixed  with  the  nitrates  of  lead  and  silver,  form 
insoluble  arseniates,  the  former  of  which  has  a white,  and  the  latter 
a brick-red  colour.! 

1058.  Sesquickloride  of  Arsenic , 2As-{-3Cl,  or  As2Cl3,  75.4  2 eq. 
arsen.  -j-  106.26  3 eq.  chlor.  — 181.66  equiv.  When  arsenic  in 


* Liebig  Ann.  xxiii.  217  . 

t For  minute  details,  the  manipulation,  precautions,  sources  of  error,  &c.,  the  stu- 
dent must  be  referred  to  Turner’s  Elements  p.  333  ; Christiscn  on  Poisons  ; Marsh 
on  the  separation  of  arsenic  ; Trans.  Soc.  of  Arts.  Li.  and  Edin.  Philos.  Jour . 
Oct.  1836;  Reid’s  Prac.  Chem.  341 5 Henry’s  Elem.  of  Chem,.  vol.  ii.  p.588, 
10th  edit.;  to  Murray’s  System , vol.  iii.  p.  441,  4th  edit.;  to  Bostock’s  Paper  in 
the  Edin.  Med.  and  Surg.  Jour.  vol.  v.  p.  166  ; Hume’s  Essay  in  the  Phil.  Mag. 
vol.  xxxiii.;  and  Bond.  Med.  and  Pkys.  Jour.  vol.  xxiii.;  Marcet’s  Paper,  in  the 
Medico- Chirurg.  Trans,  vol.  ii. ; Sylvester’s  Observations  in  Nicholson's  Jour.  vol. 
xxxiii. ; Beck’s  Med.  Juris,  vol.  ii. ; Traill’s  Paper , in  Boston  Jour,  of  Philos.  1, 
543 ; Edin.  Medico.  Chirurg.  Trans,  vol.  ii. 

From  late  investigations  arsenic  possesses  the  property  of  preserving  from 
decay  the  bodies  of  those  poisoned  with  it.  The  antiseptic  effects  sometimes 
extend  only  to  the  stomach  and  intestines,  that  is,  to  the  parts  directly  in  contact 
with  it ; but  in  some  instances  the  whole  body  is  preserved.  The  stomach  and  in- 
testines of  persons  killed  with  arsenic  have  been  found  entire  and  firm  at  the  dis- 
tance of  five,  six,  and  fourteen  months,  or  even  of  two  years  and  a half  after  death  ; 
and  in  some  of  these  instances  the  poison  itself  was  detected.  Edin.  Philos.  Jour. 
vii.  381. 

A voltaic  battery  made  to  act  on  a little  arsenious  solution  placed  on  a bit  of  glass, 
develops  metallic  arsenic  at  the  negative  pole,  and  if  this  wire  be  copper,  it  will  be 
whitened  like  tombac. 

t Protochloride  of  Arsenic.  As+Cl,  or  AsCl,  37.7  1 eq.  arsen.  + 35.42  1 eq.  chlor. 

73.12  equiv.  It  is  prepared  by  introducing  into  a tubulated  retort  a mixture  of 
arsenious  acid  with  ten  times  its  weight  of  concentrated  sulphuric  acid ; and  after 
raising  its  temperature  to  near  212°,  fragments  of  sea-salt  are  thrown  in.* 

* See  Quart.  Jour.  <Stoten.  N.  S.  i.  225. 


Sect.  vr. 


Arsenic 

acid. 


Decompos- 

ed. 


Sesqui- 

chloride. 


Protochlori<l«. 


276 


Metals — Arsenic . 


Chap.  IV. 


Arsenic 
and  hydro- 
gen. 


Decompos- 

ed. 


Action  of 
chlorine. 


Effect  of 
heat,  &c. 


Composi- 

tion. 


powder  is  thrown  into  a jar  full  of  dry  chlorine  gas,  it  takes  fire 
and  sesquichloride  of  arsenic  is  generated ; and  the  same  compound 
may  be  formed  by  distilling  a mixture  of  six  parts  of  corrosive 
sublimate  with  one  of  arsenic.  It  is  a colourless  volatile  liquid 
which  fumes  strongly  oh  exposure  to  the  air,  hence  called  fuming 
liquor  of  arsenic , and  is  resolved  by  water  into  hydrochloric  and  ar- 
senious  acids.* 

1059.  Arseniuretted  Hydrogen , 2As-f-3H,  or  As2H3,  75.4  2 eq. 
arsen.  + 3 3 eq.  hydrog.  = 78.4  equiv.  When  arsenic  is  present- 
ed to  nascent  hydrogen  a portion  of  the  metal  combines  with  the 
gas. 

The  compound  is  obtained  by  adding  a portion  of  metallic  arsenic,  or  of 
white  arsenic,  to  the  mixture  of  zinc  and  dilute  sulphuric  acid  usually  employed 
for  the  production  of  hydrogen.  It  may  also  be  obtained  by  acting  on  water 
with  a triple  alloy  of  arsenic,  potassium,  and  antimony.  This  alloy  may  be 
formed  by  heating  strongly,  for  two  hours,  in  a close  crucible,  two  parts  of  anti- 
mony, two  of  cream  of  tartar,  and  one  of  white  arsenic.  When  two  or  three 
drachms  of  this  alloy  are  thrown  quickly  under  a jar  inverted  in  water,  abun- 
dance of  arseniuretted  hydrogen  is  disengaged. 

The  greatest  caution  should  be  used  to  avoid  its  deleterious  effects, 
which  were  fatal  to  M.  Gehlen.t  The  gas  may  be  collected  over 
water,  which,  however,  absorbs  one  fifth. 

1060.  It  suffers  gradual  decomposition  when  mixed  with  atmos- 
pheric air,  water  being  formed,  and  metallic  arsenic,  together  with  a 
little  oxide,  deposited.  With  iodine  it  yields  hydriodic  acid  gas  and 
iodide  of  arsenic,  and  sulphur  and  phosphorus  produce  analogous 
changes.  By  its  action  on  salts  of  the  easily  reducible  metals,  such 
as'silver  and  gold,  the  metal  is  revived,  and  its  oxygen  uniting  with 
the  elements  of  the  gas  constitutes  arsenious  acid  and  water. 

It  is  decomposed  by  chlorine,  bubbles  of  which  may  be  passed  up 
into  a jar  of  arseniuretted  hydrogen,  standing  over  warm  water  ; 
flame  and  explosion  are  often  produced,  hydrochloric  acid  is  formed 
and  the  metal  set  free.  But  if  the  gas  be  passed  in  the  same  way 
into  chlorine,  no  inflammation  results,  absorption  takes  place,  and 
hydrochloric  acid  and  chloride  of  arsenic  are  formed.  If  the  chlo- 
rine be  not  very  pure,  and  when  the  gases  are  cold,  inflammation 
seldom  follows  their  mixture.  B.  ii.  123. 

1061.  Arseniuretted  hydrogen  in  a glass  tube  is  completely  de- 
composed by  the  heat  of  a spirit-lamp,  and  its  hydrogen  occupies  one 
and  a half  as  much  space  as  when  in  combination.  When  mixed 
with  oxygen,  and  detonated  by  the  electric  spark,  each  volume  of 
the  gas,  in  forming  water  and  arsenious  acid,  requires  one  and  a 
half  its  volume  of  oxygen  gas.  The  oxygen,  therefore,  is  equally 
divided  between  the  arsenic  and  hydrogen  ; and  arseniuretted  hy- 
drogen consists  of  two  equivalents  of  arsenic  and  three  of  hydrogen. 
By  volume,  it  is  composed  of  half  a volume  of  the  vapour  of  arsenic, 
and  three  vols.  of  hydrogen,  condensed  into  two  volumes.! 


Sulphur ets  of  Arsenic. 

Sulphurets  1062.  Protosulphuret  of  Arsenic , As-|-S,  or  AsS,  37.7  1 eq. 

arsen.  + 16.1  1 eq.  sulph.  = 53.8  equiv.  Sulphur  unites  with 


* Dr  Davy.  t Ann.  de  Ckim.  et  Phys.  iii.  135.  t Ann.  de  Chim.x liii.  407. 


Chromium . 277 

irsenic  in  at  least  three  proportions,  forming  compounds,  two  of  Sect,  vi. 
vhich  occur  in  the  mineral  kingdom,  and  are  well  known  by  the 
lames  of  realgar  and  orpiment.  Realgar  or  the  protosulphur et 
nay  be  formed  artificially  by  heating  arsenious  acid  with  about  half 
ts  weight  of  sulphur,  until  the  mixture  is  brought  into  a state  of 
lerfect  fusion.  The  cooled  mass  is  crystalline,  transparent,  and  of 
i ruby  red  colour ; and  may  be  sublimed  in  close  vessels  without 
change. 

1063.  Orpiment , or  Sesquisulphuret  of  Arsenic}  2As+3S,  or  n • 

^sS3,  75.4  2 eq.  arsen.  + 48.3  3 eq.  sulph.  = 123,7  equiv.,  may  P 
ie  prepared  by  fusing  together  equal  parts  of  arsenious  acid  and 
sulphur  ; but  the  best  mode  of  obtaining  it  quite  pure  is  by  trans- 
nitting  a current  of  hydrosulphuric  acid  gas  through  a solution  of 
irsenious  acid.  Orpiment  has  a rich  yellow  colour,  fuses  readily 
vhen  heated,  and  becomes  crystalline  on  cooling,  and  in  close  ves- 
sels may  be  sublimed  without  change.  It  is  dissolved  with  great 
facility  by  the  pure  alkalies,  and  yields  colourless  solutions. 

1064.  Orpiment  is  employed  as  a pigment,  and  is  the  colouring  Uses 
3rinciple  of  the  paint  called  King's  yellow . Braconnot  has  proposed 

t likewise  for  dyeing  silk,  woollen,  or  cotton  stuffs  of  a yellow  colour ; 
he  cloth  being  soaked  in  a solution  of  orpiment  in  ammonia,  and 
;hen  suspended  in  a warm  apartment.  The  alkali  evaporates,  and 
eaves  the  orpiment  permanently  attached  to  the  cloth. # 

1065.  Persulphuret  of  Arsenic , 2As+5S,  or  As2S5,  75.4  2 eq.  persuiphu= 
?q.  arsen.  + 80.5  5 eq.  sulph.  = 155.9  equiv.,  is  prepared  by  trans-  ret. 
pitting  hydrosulphuric  acid  gas  through  a moderately  strong  solu- 

;ion  of  arsenic  acid ; or  by  saturating  a solution  of  arseniate  of  po- 
;assa  or  soda  with  the  same  gas,  and  acidulating  with  hydrochloric 
)r  acetic  acid.  The  oxygen  of  the  acid  unites  with  the  hydrogen 
)f  the  gas,  and  persulphuret  of  arsenic  subsides.  In  colour  it  is 
fery  similar  to  orpiment.f 

1066.  Arsenic  forms  alloys  with  most  of  the  metals,  and  they  Alloys, 
ire  generally  brittle. 

1067.  Arsenic  is  used  in  a variety  of  the  arts.  It  enters  into  me-  Uses. 
;allic  combinations,  wherein  a white  colour  is  required.  Glass 
nanufacturers  use  it ; but  its  effect  on  the  composition  of  glass 
ioes  not  seem  to  be  clearly  explained. 

Chromium. 

Symb.  Cr  Eq.  28 

1068.  Chromium!  was  discovered  by  Vauquelin  in  1797,  in  a Discovery 
Deautiful  red  mineral,  the  native  dichromate  of  oxide  of  lead.  It 

lias  since  been  detected  in  the  mineral  called  chromate  of  iron , a 
compound  of  the  sesquioxides  of  chromium  and  iron  which  occurs 
in  several  places  in  Europe  and  in  this  country. 


* An.  dc  Ch.  et  de  Ph.  xii. 

+ The  experiments  of  Orfila  have  proved  that  the  sulphurets  of  arsenic  are  poison- 
ms,  though  in  a much  less  degree  than  arsenious  acid.  The  precipitated  sulphuret 
is  more  injurious  than  the  native  orpiment.  The  antidote  to  arsenious  acid  is  hy. 
irated  sesquioxide  of  iron.  (Bunson.) 

t From  Xqw[i a,  colour , indicative  of  its  remarkable  tendency  to  form  coloured 
compounds. 


I 


278 


Chap  IV. 

How  ob- 
tained. 


Properties, 

&c. 


Sesquiox- 

ide. 


Crystals. 


Wohler’s 

process. 


Properties. 


Solubility, 

&c. 


Salts  of. 


JHetals — Chromium . 

1069.  Chromium,  which  has  been  procured  in  small  quantity, 
owing  to  its  powerful  attraction  for  oxygen,  may  be  obtained  by  ex- 
posing the  sesquioxide  of  chromium  mixed  with  charcoal  to  the 
most  intense  heat  of  a smith’s  forge. 

A more  convenient  process  is  to  decompose  the  sesquichloride  by 
heat  and  ammoniacal  gas,  in  which  case,  the  metal  has  a chocolate-  , 
brown  colour.  In  this  finely  divided  state,  it  takes  fire  when  heated 
in  the  open  air.* 

1070.  It  is  a brittle  metal,  of  a grayish  white  colour,  and  very 
infusible.  Its  sp.  gr.  is  5.9. 

When  fused  with  nitre  it  is  oxidized,  and  converted  into  chromic 
acid.  With  a smaller  quantity  of  oxygen  it  forms  the  green  or  ses- 
quioxide. 

1071.  Sesquioxide  of  Chromium , 20+30,  Cr,  or  Cr203,  56  2 
eq  chrom.  + 24  3 eq.  oxy.  — 80  equiv.  This,  the  only  known 
oxide  of  chromium,  is  prepared  by  dissolving  chromate  of  potassa  in 
water,  and  mixing  it  with  a solution  of  nitrate  of  protoxide  of  mercu- 
ry; when  an  orange  coloured  precipitate,  chromate  of  that  oxide, 
subsides.  On  heating  this  salt  to  redness  in  an  earthen  crucible,  j 
the  mercury  is  dissipated  in  vapour,  and  the  chromic  acid  is  resolved 
into  oxygen  and  sesquioxide  of  chromium. 

1072.  It  may  also  be  obtained  in  small  tabular  crystals  by  ex- 
posing the  bichromate  of  potassa  to  a strong  red  heat;  1 eq.  of 
chromic  acid  loses  oxygen,  while  the  other  forms  a neutral  salt  with 
the  potassa.  The  latter  is  readily  removed  by  boiling  water. 

1073.  Wohler  has  obtained  this  oxide  in  fine  crystals  by  conduct- 
ing the  vapour  of  the  oxychloride  of  chromium  (formerly  terchloride)  j 
through  a red-hot  glass  tube  ; it  is  decomposed  and  the  sesquioxide 
is  deposited  in  fine  crystals,  a mixture  of  oxygen  and  chlorine  gases 
is  evolved. 

1074.  As  obtained  by  either  of  the  first  processes,  it  is  a green 
powder ; but  the  crystals  of  Wohler  are  black,  and  possess  a strong 
metallic  lustre,  resembling  specular  iron  ore  ; it  is  as  hard  as  corun- 
dum, and  has  a sp.  gr.  of  5.21  ; its  powder  is  green. 

1075.  It  is  insoluble  in  water,  and  after  being  strongly  heated  re- 
sists the  action  of  the  strongest  acids.  It  is  oxidized  when  defla- 
grated  with  nitre.  It  communicates  a green  colour  to  borax,  a good  I 
test  of  its  presence,  and  a useful  property  in  the  arts.  To  it  the  j 
emerald  owes  its  colour. 

1076.  Sesquioxide  of  chromium  is  a salifiable  base,  and  its  salts, 
which  have  a green  colour,  may  easily  be  prepared  in  the  following  | 
manner. 

To  a boiling  solution  of  chromate  of  potassa  in  water,  equal  measures  of  strong  i 
hydrochloric  acid  and  alcohol  are  added  in  successive  small  portions,  until  the 
red  tint  of  the  chromic  acid  disappears  entirely,  and  the  liquid  acquires  a pure  ; 
green  colour.  On  pouring  an  excess  of  pure  ammonia  into  this  solution,  a pale 
green  bulky  hydrate  subsides,  which  consists  of  one  equivalent  of  the  oxide  and 
twentysix  equivalents  of  water.t 

The  oxide,  in  this  state,  is  readily  dissolved  by  acids.  On  expel- 
ling the  water  by  heat,  the  sudden  approximation  of  the  particles, 


* An.  de  Ch.  et  de  Ph.  xlviii.  297. 


t Thomson. 


Chromic  Acid . 


279 


•hich  abruptly  occurs  at  a certain  temperature,  causes  such  intense  Sect,  vr. 
solution  of  heat  that  the  whole  mass  becomes  vividly  incandescent. 

The  anhydrous  sesquioxide  is  formed  when  bichromate  of  potassa 
briskly  boiled  with  sugar  and  a little  hydrochloric  acid. 

1077.  Chromic  Acid , Cr+30,  Cr,  or  CrO3,  28  1 eq.  chr.  + 24  3 chromic 
p oxy.  = 52  equiv.,  may  be  procured  from  the  ore  called  chromate  acid- 

? iron * by  the  following  process. 

Reduce  the  ore  to  fine  powder,  heat  it  red-hot  for  two  hours,  mixed  with  half  process. 

3 weight  of  nitre  ; wash  the  contents  of  the  crucible,  and  add  to  the  lixivium 
trie  acid  to  neutralize  the  excess  of  potassa ; a solution  of  nitrate  and  chromate 
’potassa  is  obtained.  Upon  adding  nitrate  of  lead  to  this  solution,  chromate  of 
ad  is  precipitated  in  the  form  of  a yellow  powder,  which  is  to  be  washed,  dried, 
id  heated  to  redness.  Of  this  chromate  four  parts  are  then  well  mixed  with 
iree  of  finely  powdered  and  pure  fluor  spar  (previously  heated  red-hot),  and  five 
' highly  concentrated  sulphuric  acid ; this  mixture  is  introduced  into  a distilla- 
ry apparatus  of  lead  or  platinum,  and  gently  heated  ; a red  vapour  is  liberated, 
hich  is  conducted  into  distilled  water  contained  in  a vessel  of  platinum  ; it  is 
len  condensed  into  a dark  orange-coloured  liquid  ; the  red  vapour  is  a fluoride 
” chromium,  and  is  resolved  by  water  into  hydrofluoric  and  chromic  acids,  the 
dution  of  which,  evaporated  in  a platinum  vessel,  leaves  pure  chromic  acid.  If, 
istead  of  conducting  the  vapour  into  water,  it  be  received  into  a platinum  ves- 
d,  containing  pieces  of  moist  blotting  paper,  it  is  decomposed  as  before ; but  the 
iromic  acid  is  deposited  in  beautiful  acicular  crystals  which  soon  deliquesce.  B. 

It  may  be  obtained  by  dropping  hydrochloric  acid  into  a mixture  of  chromate 
' silver  and  distilled  water,  until  the  red  brown  colour  is  reduced  to  white  with  Hayes’s 
tinge  of  red  ; at  the  same  time  filtering  and  cautiously  adding  a few  drops  of  process, 
ydrochloric  acid,  till  a white  precipitate  ceases  to  be  formed.  When  large  quan- 
ties  are  required,  the  bichromate  of  lead  may  be  added  to  strong  hydrochloric 
fid,  and  the  mixture  placed  on  a warm  sand-bath  for  a few  hours,  occasionally 
irring  the  mass.  Water  may  then  be  added,  and  filtered  from  the  chloride  of 
sad,  and  the  filtered  fluid  used  instead  of  the  hydrochloric  acid  in  decomposing 
le  chromate  of  silver  ; in  either  process  a solution  of  pure  chromic  acid  is  ob- 
ined.t 

1078.  Chromic  acid,  according  to  Turner,  is  black  while  warm,  pr0perties 
nd  of  a dark  red  colour  when  cold  ; according  to  Hayes  it  is  yel- 
jwish-brown  when  dry.  It  is  very  soluble  in  water,  rendering  it 

sd  or  yellow  according  to  the  degree  of  dilution  ; when  the  solution 
3 concentrated  by  heat  and  allowed  to  cool  it  deposits  red  crystals 
/hich  are  deliquescent.  The  solution  has  an  acid  and  astringent 
iste,  it  bleaches  litmus  and  blue  paper. 

1079.  Chromic  acid  is  converted  into  the  sesquioxide,  with  evolution  De0xidiz- 
f oxygen,  by  exposure  to  a strong  heat.  It  is  more  or  less  com- ed. 
iletely  converted  into  the  oxide  by  being  boiled  with  sugar,  starch, 

r various  other  organic  principles.  It  destroys  the  colour  of  indigo, 
nd  of  most  vegetable  and  animal  colouring  matters  ; a property  ad- 


* Hnyes  in  Amer.  Jour.  xiv.  136. 

t Another  method  consists  in  decomposing  a hot  concentrated  solution  of  bichro-  Maiia,g 
tiate  of  potassa  by  silicaled  hydrofluoric  acid.  The  chromic  acid,  after  being  sepa-  method, 
ated  from  the  sparingly  soluble  fluoride  of  silicon  and  potassium,  is  evaporated  to 
iryness  in  a platinum  capsule,  and  then  redissolved  in  the  smallest  possible  quantity 
f water.  By  this  means  the  last  portions  of  the  double  salt  are  rendered  insoluble, 
nd  the  pure  chromic  acid  may  be  separated  by  decantation.  The  acid  must  not  be 
titered  in  this  concentrated  state,  as  it  then  corrodes  paper  like  sulphuric  acid,  and  is 
onverted  into  chromate  of  the  sesquioxide  of  chromium.  When  it  is  wished  to  pre- 
tare  a large  quantity  of  chromic  acid  by  this  process,  porcelain  vessels  may  be  safely 
mployed  in  the  first  part  of  the  operation,  provided  care  is  taken  to  add  a quantity 
if  silicated  hydrofluoric  acid  not  quite  sufficient  for  precipitating  the  whole  of  the  po- 
assa.  Edin.  Jour,  of  Sci.  viii.  175  ; see  also  Henry’s  Chem.  ii.  62,  Brewster’s  Jour . 

:vii.  175,  and  Gray’s  Oper.  Chem.  750. 


280 


Metals — Vanadium. 


Chap.  iV. 
Colour,  &c. 

Process. 


Properties. 


Oxyehlo- 

ride. 


Discovery. 


Process. 


Appear- 
ance, &c. 


vantageously  employed  in  calico  printing,  and  which  manifestly 
depends  on  the  facility  with  which  it  is  deprived  of  oxygen. 

1080.  Chromic  acid  is  characterized  by  its  colour,  and  by  forming 
coloured  salts  with  alkaline  bases.  The  most  important  of  these 
salts  is  chromate  of  protoxide  of  lead,  which  is  found  native  in  small 
quantity,  and  is  easily  prepared  by  mixing  chromate  of  potassa  with  a 
soluble  salt  of  lead.  It  is  of  a rich  yellow  colour,  and  is  employed 
in  the  arts  of  painting  and  dyeing  to  great  extent.* 

1081.  Perjluoride  of  Chromium.  CrF5  ? When  a mixture  of  three 
parts  of  fluor  spar  and  four  of  chromate  of  protoxide  of  lead  is  dis- 
tilled with  five  parts  of  fuming  or  even  common  sulphuric  acid  in  a 
leaden  retort,  a red-coloured  gas  is  disengaged,  which  acts  rapidly 
on  glass,  with  deposition  of  chromic  acid  and  formation  of  fluo-silicic 
acid  gas.  It  is  absorbed  by  water,  and  the  solution  is  found  to  con- 
tain a mixture  of  fluoric  and  chromic  acids.  The  watery  vapour  of 
the  air  effects  its  decomposition,  so  that  when  mixed  with  air,  red 
fumes  appear,  owing  to  the  separation  of  minute  crystals  of  chromic 
acid.  Its  true  composition  is  not  yet  determined. 

Oxychloride  of  Chromium , CrCl3-|-2Cr03,  238.26  equiv.,  was  dis- 
covered at  the  same  time  as  the  preceding,  and  was  obtained  by 
the  action  of  fuming  sulphuric  acid  on  a mixture  of  about  equal 
weights  of  chromate  of  protoxide  of  lead  and  chloride  of  sodium. 
It  is  a heavy  red  liquid,  volatile  and  yielding  red  vapours  when  ex- 
posed to  the  air.  It  is  decomposed  by  water  into  hydrochloric  and 
chromic  acids. 

Vanadium. 

Symb.  V Equiv.  68.5 

1082.  Vanadium,  so  called  from  Vanadis,  the  name  of  a Scandi- 
navian Deity,  was  discovered  in  the  year  1830,  by  Sefstrom,  of  Fah- 
lun,  in  iron  prepared  from  the  iron-ore  of  Taberg,  in  Sweden.  He 
afterwards  found  a more  abundant  source  in  the  slag  or  cinder 
formed  during  the  conversion  of  the  cast  iron  of  Taberg  into  the  mal- 
leable iron.  Soon  after,  the  same  metal  was  found,  by  Johnson,  in  a 
a mineral  from  Wanlock-head,  in  Scotland,  where  it  occurs  as  a va- 
nadiate  of  protoxide  of  lead.  A similar  mineral,  found  at  Zimapan 
in  Mexico,  was  examined  in  the  year  1801  by  del  Rio. 

1053.  Vanadium  was  obtained  by  a complicated  process!  from  the 
slag,  but  may  be  more  easily  procured  from  native  vanadiate  of  lead. 

The  ore  is  dissolved  in  nitric  acid,  the  lead  and  arsenic  are  precipitated  by  hy- 
drosulphuric  acid,  a blue  solution  is  formed  and  evaporated  to  dryness.  The  re- 
sidue is  dissolved  by  ammonia,  and  the  vanadiate  of  amfmonia  precipitated  by  a 
piece  of  sal  ammoniac.  The  vanadic  acid  is  thus  separated  from  arsenic,  phos- 
phoric, and  hydrochloric  acids  with  which  it  is  generally  associated. 

1054.  Vanadium  was  separated  in  a pulverulent  state,  by  means  of 
potassium,  having  but  little  tenacity  or  appearance  of  a metal.  But 


* Sesquichloride  of  Chromium.  2CH-3C1,  or  Cr‘2Cl3,  56  2 eq.  chrom.  + 106.26  3 
eq.  chlor.  = 162.26  equiv.  It  is  prepared  by  transmitting  dry  chlorine  gas  over  a mix- 
ture of  oxide  of  chromium  and  charcoal  heated  to  redness  in  a tube  of  porcelain  ; when 
the  sesquichloride  gradually  collects  as  a crystalline  sublimate  of  a peach-purple  co- 
lour, which  in  thin  layers  is  transparent,  but  in  thicker  masses  is  opaque.  The  ses- 
quichloride of  chromium  dissolves  slowly  forming  a deep  green  solution. 

+ For  the  details  see  Turner’s  Elements,  314. 


Vanadic  Acid . 281 

binder  strong  pressure  it  assumed  a lustre  like  that  of  graphite.  By  Sect,  vi. 
a process  of  Rose’s  it  had  more  of  a metallic  appearance,  a white 
colour,  and  strong  lustre. 

1085.  It  is  so  extremely  brittle  that  it  cannot  be  removed  with- 
out falling  into  powder.  It  is  not  oxidized  either  by  air  or  water ; Properties, 
although  by  continued  exposure  to  the  air  its  lustre  gradually  grows 
weaker,  and  it  acquires  a reddish  tint.  It  is  not  dissolved  by  boiling 
sulphuric,  hydrochloric,  or  hydrofluoric  acid  ; but  by  nitric  and  nitro- 
hydrochloric  acid  it  is  attacked,  and  the  solution  has  a beautiful  dark 

blue  colour.  It  is  not  oxidized  by  being  boiled  with  caustic  potassa, 
nor  by  carbonated  alkalies  at  a red  heat. 

1086.  Protoxide  of  Vanadium.  V-f-O,  V,  or  VO,  68.5  1 eq.  Protoxide, 
vanad.  -(-8  1 eq.  oxy.  ==  76.5  equiv.  This  compound  is  readily 
formed  from  vanadic  acid  by  the  combined  agency  of  heat  and  char- 
coal or  hydrogen  gas.  When  rendered  coherent  by  compression  it 
possesses  a property  very  unusual  in  oxides,  that  of  conducting 
electricity,  and  in  relation  to  zinc  of  being  as  strongly  electro-nega- 
tive as  silver  or  copper. 

1087.  Binoxide  of  Vanadium.  V-f-20,  V,  or  VO2,  68.5  1 eq.  Binoxide. 
vanad.  + 16  2 eq.  oxy.  =±  84.5  equiv.  This  oxide  is  best  prepared, 

in  the  dry  way,  by  heating  to  full  redness  an  intimate  mixture  of  10 
parts  of  the  protoxide  with  12  of  vanadic  acid  in  a vessel  filled  with 
carbonic  acid,  or  from  which  combustible  matter  on  the  one  hand, 
and  oxygen  gas  on  the  other,  are  carefully  excluded. 

The  salts  of  the  binoxide  of  vanadium  are  distinguished  by  their 
blue  colour,  and  by  forming  with  solution  of  gall-nuts  a black  com- 
pound, a tannate  of  the  binoxide,  very  similar  to  ink. 

The  binoxide  is  disposed  to  act  the  part  of  an  acid  by  uniting  with 
alkaline  bases,  with  which  it  forms  definite  and  in  some  cases  crys- 
talline compounds. 

1088.  Vanadic  Acid , V-f-30,  V,  or  VO3,  68.5  1 eq.  vanad.  24  Vanadic 
3 eq.  oxy.  = 92.5  equiv.,  is  tasteless,  insoluble  in  alcohol,  and  very  aci4 
slightly  soluble  in  water,  which  takes  up  rather  less  than  ttfW  °f  hs 

of  its  weight,  acquiring  a yellow  colour  and  an  acid  reaction.  Heat- 
ed with  combustible  matter  it  is  deoxidized,  being  converted  into  the 
protoxide  or  binoxide,  or  mixtures  of  these  oxides.  In  solutions  it  is 
deprived  of  oxygen  by  all  deoxidizing  agents. 

1089.  Vanadic  acid  unites  with  salifiable  bases  often  in  two  or  Salts  0fj 
more  proportions,  forming  soluble  salts  with  the  alkalies,  and  in  ge- 
neral sparingly  soluble  salts  with  the  other  metallic  oxides.  Those 

with  excess  of  acid  are  commonly  of  a red  or  orange-red  colour. 

Most  of  the  neutral  salts  are  yellow. 

Vanadic  acid  is  distinguished  from  all  other  acids  except  the  chro- 
mic by  its  colour,  and  from  this  acid  by  the  action  of  deoxidizing 
substances,  which  give  a blue  solution  with  the  former  and  a green 
with  the  latter. 

1090.  Sulphureis.  When  the  binoxide  of  vanadium  is  heated  to  Sulphury, 
redness  in  a current  of  hydrosulphuric  acid  gas,  it  is  converted  into 
protoxide,  and  both  water  and  sulphur  are  obtained  : on  continuing 

the  process  the  protoxide  is  decomposed,  hydrogen  gas  and  water 
36 


282 


Chap  IV. 


Tersulphu- 

ret. 


Ore. 


Properties. 

Molybde- 
num and 
oxygen. 

Protoxide. 

Binoxide. 


Hydrate. 


Anhydrous. 


Molybdic 

acid. 


Metals — Molybdenum. 

pass  over,  and  bisulphuret  of  vanadium  is  generated.  (Bisulphuret 
of  Vanadium,  V-f-2S,  or  VS2,  68.5  1 eq.  vanad.  -f-  32.2  2 eq.  sulph. 
= 100.7  equiv.) 

1091.  When  a solution  of  vanadic  acid  in  hydrosulphate  of  ammo- 
nia is  acidulated  by  hydrochloric  or  sulphuric  acid,  the  hydrated  ter - 
sulphuret  of  vanadium  subsides.  Its  colour  is  of  a much  lighter  brown 
than  the  bisulphuret,  becomes  almost  black  in  drying,  and  is  resolved 
by  a red  heat  in  close  vessels  into  the  bisulphuret,  with  loss  of  water 
and  sulphur.* 

Molybdenum. 

Symb.  Mo  Equiv.  47.7 

1092.  The  sulphuret  is  the  most  common  natural  compound  of 
this  metal. 

When  this  ore,  in  fine  powder,  is  digested  in  nitro-hydrochloric  acid  until 
completely  decomposed,  and  the  residue  is  briskly  heated,  in  order  to  expel  sul- 
phuric acid,  molybdic  acid  remains  in  the  form  of  a white  heavy  powder  From 
this  acid  metallic  molybdenum  may  be  obtain*  d by  exposing  it  with  charcoal  to  the 
strongest  heat  of  a smith’s  forge ; or  by  conducting  over  it  a current  of  hydrogen 
gas  while  strongly  heated  in  a tube  of  porcelain. t 

1093.  Molybdenum  is  a brittle  metal,  very  infusible,  and  of  a 
while  colour,  ft  has  been  procured  but  in  small  quantities,  and  its 
properties  are  known  imperfectly.  Its  sp.  gr.  is  8.615.  When 
heated  in  open  vessels  it  absorbs  oxygen,  and  is  converted  into  mo- 

lybdic  acid. 

1094.  Protoxide  of  Molybdenum.  Mo~(-0,  Mo  or  MoO,  47.71  eq, 
molyb.  -f  8 1 eq.  oxy.  = 55.7  equiv.  This  oxide  is  obtained, 
according  to  Berzelius,  by  precipitating  the  hydrochloric  solution  of 
molybdic  acid  by  zinc.  It  is  in  the  form  of  a brown  hydrate  and 
gives  dark  coloured  solutions  with  the  acids. 

1095.  Binoxide  of  Molybdenum,  Mo-f-20,  Mo,  or  MoO2,  47.7 
molyb.  + 16  oxy.  = 63.7  equiv.,  is  obtained  as  a deep  brown  an- 
hydrous powder  by  mixing  molybdate  of  soda  with  half  its  weight  of 
sal  ammoniac  in  fine  powder,  projecting  the  mixture  into  a red-hot 
crucible  which  is  to  be  instantly  covered,  and  the  heat  continued 
until  vapours  of  sal  ammoniac  cease  to  appear. 

1096.  The  hydrate,  of  a rust-brown  colour,  may  be  formed  by 
digesting  molybdenum  in  powder  with  molybdic  acid  dissolved  in 
hydrochloric  acid,  until  the  liquid  acquires  a deep  red  colour,  and 
then  adding  ammonia;  or  by  adding  ammonia  to  a solution  of  the 
bichloride. 

1097.  The  anhydrous  binoxide  is  insoluble  in  acids  and  is  changed 
into  molybdic  acid  by  strong  nitric  acid.  The  hydrate  is  very  like 
hydrated  peroxide  of  iron,  is  dissolved  by  acids  with  which  it  forms 
red  salts,  is  insoluble  in  the  alkalies,  but  dissolves  in  alkaline  carbo- 
nates. It  is  soluble,  though  sparingly,  in  pure  water. 

1098.  Molybdic  Acid.  Mo-f-30,  0r  MoO3,  47.7  1 eq.  molyb.  -j- 
24  3 eq.  oxy.  = 71.7  equiv.  When  sulphuret  of  molybdenum  is 
roasted  in  an  open  crucible  kept  at  a low  red  heat,  and  stirred  until 
sulphurous  acid  ceases  to  escape,  a dirty  yellow  powder  is  left, 
which  contains  impure  molybdic  acid.  The  acid  is  taken  up  by  arn- 


* See  Turner,  347. 


+ Berzelius- 


283 


Tungsten—  Tungstic  Acid . 

monia  and  the  filtered  solution  evaporated  to  dryness  ; it  is  again  Sect,  vi. 
taken  up  by  water,  a little  ammonia  being  added,  and  filtered ; and 
it  is  then  purified  by  crystallization.  On  heating  gently  in  an  open 
platinum  crucible,  taking  care  to  prevent  fusion,  the  ammonia  is  ex- 
pelled, and  the  pure  acid  remains.  It  is  also  obtained  by  oxidizing 
the  binoxide  with  nitric  acid. 

Molybdic  acid  is  a white  powder,  of  sp.  gr.  3.49,  fusible  by  a red 
heat  into  a yellow  liquid.  It  requires  570  times  its  weight  of  water 
for  solution.  It  is  soluble  in  the  alkalies,  forming  colourless  molyb- 
dates, from  which  molybdic  acid  is  precipitated  by  the  stronger  acids. 

1099.  Sulphurets.  Molybdenum  combines  with  sulphur  in  three  Sulphurets. 
proportions.  The  lowest  grade  is  the  bisulphuret , which  is  the  most 
common  ore  of  molybdenum,  and  is  usually  associated  with  ores  of 

tin,  has  a lead-gray  colour  and  metallic  lustre  resembling  graphite, 
for  which  it  was  formerly  mistaken.  Its  density  varies  from  4.138 
to  4.569.  It  bears  a strong  heat  in  close  vessels  without  change, 
but  is  oxidized  by  nitric  acid. 

Tungsten . 

Synth.  W Equiv.  94.8 

1100.  Tungsten,  or  Tungstenum,  signifies  a heavy  stone , and  is 

a name  given  by  the  Swedes  to  a mineral,  which  Scheele  found  to  Tungsten, 
contain  a peculiar  metal,  as  he  supposed  in  the  state  of  an  acid, 
united  with  lime.  The  same  metallic  substance  was  afterwards 
found  united  with  iron  and  manganese  in  wolfram. 

1101.  The  metal  ia  obtained  by  exposing  a mixture  of  tungstic 
acid  and  charcoal  to  a strong  heat.  It  is  difficult  of  fusion,  very 
hard,  brittle,  and  of  an  iron  colour.  Its  sp.  gr.  is  17.5.  By  the  ac- 
tion of  heat  and  air,  tungsten  is  converted  into  tungstic  acid. 

1102.  Wolfram  is  found  in  primitive  countries  generally  accom-  Wolfram, 
panying  tin  ores  ; its  colour  is  brownish  black  ; it  occurs  massive 

and  crystallized.* 

1103.  Binoxide  of  Tungsten , W-j-20,  W,  or  WO2,  94.8  1 eq.  Binoxide. 
tungst.  -j-  16  2 eq.  oxy.  ==  110.8  equiv.,  is  formed  by  the  action  of 
hydrogen  gas  on  tungstic  acid  at  a low  red  heat ; but  the  best  mode  of 
procuring  it  both  pure  and  in  quantity,  is  that  recommended  by 
Wohler. 

Binoxide  of  tungsten,  when  prepared  by  means  of  hydrogen  gas,  properties. 
has  a brown  colour,  and  when  polished  acquires  the  colour  of  copper  ; 
but  when  procured  by  Wohler’s  process,  it  is  nearly  black.  It  does 
not  unite,  so  far  as  is  known,  with  acids;  and  when  heated  to  near 
redness,  it  takes  fire  and  yields  tungstic  acid. 

1104.  Tungstic  Acid.  W+30,  W,  WO3,  94.8  1 eq.  tungst.  + 

24  3 eq.  oxy.  — 118.8  equiv.  A convenient  method  of  preparing  jfc'id5811® 
tungstic  acid  is  by  digesting  native  tungstate  of  lime,t  very  finely 
levigated,  in  nitric  acid  ; by  which  means  nitrate  of  lime  is  formed, 


* For  Wohler’s  process  for  obtaining  the  binoxide  from  this  ore,  see  Quart.  Jour, 
of  Sci.  xx.  177,  and  Turner,  p.  352. 

t A whitish  semi-transparent  substance,  found  in  England,  Saxony,  Bohemia,  and 
Sweden,  and  occurring  crystallized  and  massive.  Its  most  usual  form  is  the  octohe-  "fstate 
dron. 


284 


Metals — Columbium. 


Chap.  IV. 


Chlorides. 


Bisulphu- 

ret. 


Discovery. 


Tantalite 
and  yttro- 
tantalite. 
Tantalum. 


Columbic 

acid. 


Properties. 


and  tungstic  acid  separated  in  the  form  of  a yellow  powder.  Tung- 
stic acid  may  also  be  prepared  by  the  action  of  hydrochloric  acid  on 
wolfram.  It  is  also  obtained  by  heating  the  binoxide  to  redness  in 
open  vessels. 

Tungstic  acid  is  of  a yellow  colour,  is  insoluble  in  water,  and  has 
no  action  on  litmus  paper.  With  alkaline  bases  it  forms  salts  called 
tungstates , which  are  decomposed  by  the  stronger  acids.  Heated  in 
open  vessels,  it  acquires  a green  colour,  and  becomes  blue  when  ex- 
posed to  the  action  of  hydrogen  gas  at  a temperature  of  500°  or 
600°  F. 

1105.  Chlorides.  Tungsten  and  chlorine  unite  in  two  propor- 
tions. When  metallic  tungsten  is  heated  in  chlorine  gas,  it  takes 
fire  and  yields  the  bichloride  ; (W-f-2Cl,  or  WC12,  94.8  1 eq.  tungst. 
-f-  70.84  2 eq.  chlor.  = 165.64  equiv.)  Wohler  has  described  ano- 
ther chloride  formed  at  the  same  time  which  is  converted  by  water 
into  hydrochloric  and  tungstic  acids.  It  exists  in  beautiful  crystals 
of  a fine  red  colour. 

1106.  Bisulphurct  of  Tungsten , W-f-2S,  or  WS2,  94.8  1 eq. 
tungst.  + 32.2  2 eq.  sulph.  = 127  equiv.,  is  obtained  by  passing 
hydrosulphuric  acid  gas,  or  the  vapour  of  sulphur,  over  tungstic  acid 
heated  to  whiteness  in  a tube  of  porcelain. 

Columbium. 

Symb.  Ta  Equiv.  185 

1107.  This  metal  was  discovered  in  1801,  by  Hatchett,  in  a black 
mineral  in  the  British  museum,  which  had  been  sent  by  Gov. 
Winthrop  to  Sir  Hans  Sloane,  from  the  vicinity  of  New-London  in 
Connecticut.* 

A metal  analogous  in  its  properties  to  columbium,  was  discovered 
by  Ekeberg,  a Swedish  chemist,  in  two  different  minerals,  called 
Tantalite  and  Yttro-tantalite.  To  this  metal  he  gave  the  name  of 
tantalum.  The  identity  of  these  metals,  however,  was  established, 
in  1S09,  by  Wollaston. 

1108.  Columbic  acid  is  with  difficulty  reduced  to  the  metallic 
state  by  the  action  of  heat  and  charcoal ; but  Berzelius  succeeded  in 
obtaining  this  metal  by  the  same  process  which  he  employed  in  the 
preparation  of  zirconium  and  silicon,  namely,  by  heating  potassium 
with  the  double  fluoride  of  potassium  and  columbium.  On  washing 
the  reduced  mass  with  hot  water,  columbium  is  left  in  the  form  of  a 
black  powder.  In  this  state  it  does  not  conduct  electricity  ; but  in  a 
denser  state  it  is  a perfect  conductor.  By  pressure  it  acquires  me- 
tallic lustre,  and  has  an  iron-gray  colour. 

1 109.  It  is  not  fusible  at  the  temperature  at  which  glass  is  fused. 
When  heated  in  the  open  air,  it  takes  fire  yielding  columbic  acid. 
It  is  dissolved  with  heat  and  disengagement  of  hydrogen  gas  by  hy- 
drofluoric acid,  and  still  more  easily  by  a mixture  of  nitric  and 
hydrofluoric  acids.  It  is  also  converted  into  columbic  acid  by  fusion 
with  hydrate  of  potassa,  the  hydrogen  gas  of  the  water  being 
evolved. 


* Probably  Haddam,  where  it  was  rediscovered  by  Torrey  ( Amer . Jour.  iv.  52).  A 
crystal  weighing  fourteen  pounds  was  found  by  Johnson,  Ibid,  xxx.  3S7. 


Sesquioxide  of  Antimony. 


285 


1110.  Binoxide  of  Columbium , Ta+20,  fa,  or  TaO2,  185  1 eq.  . Sect;..YI- 
columb.  — |—  16  2 eq.  oxy.  = 201  equiv.,  is  generated  by  placing  co-  Binoxide. 
lumbic  acid  in  a crucible  lined  with  charcoal,  luting  carefully  to 
exclude  atmospheric  air,  and  exposing  it  for  an  hour  and  a half  to 
intense  heat.  When  reduced  to  powder  its  colour  is  dark  brown. 

It  is  not  attacked  by  any  acid,  but  it  is  converted  into  columbic  acid 
either  by  fusion  with  hydrate  of  potassa,  or  deflagration  with  nitre. 

1111.  Columbic  Acid.  Ta-{-30,  fa,  or  TaO3,  185  1 eq.  columb.  Columbie 
+ 24  3 eq.  oxy.  = 209  equiv.  Columbium  exists  in  most  of  its  acid- 
ores  as  an  acid,  united  either  with  the  oxides  of  iron  and  manganese, 

as  in  tantalite,  or  with  the  earth  yttria,  as  in  the  yttro-tantalite.  This 
acid  is  obtained  by  fusing  its  ore  with  three  or  four  times  its  weight 
of  carbonate  of  potassa,  when  a soluble  columbate  of  that  alkali  re- 
sults, from  which  columbic  acid  is  precipitated  as  a white  hydrate  by 
acids. 

1112.  Hydrated  columbic  acid  is  tasteless  and  insoluble  in  water  ; Properties, 
but  when  placed  on  moistened  litmus  paper,  it  communicates  a red 

tinge.  It  is  dissolved  by  the  sulphuric,  hydrochloric,  and  some  ve- 
getable acids ; but  it  does  not  appear  to  form  definite  compounds 
with  them.  With  alkalies  it  unites  readily ; when  the  hydrated  acid 
is  heated  to  redness,  water  is  expelled,  and  the  anhydrous  colum- 
bic acid  remains. 

Antimony. 

Symb.  Sb  Equiv.  64.6 

1113.  This  metal  is  found  native  in  Sweden,  in  France,  and  in  0reg 
the  Hartz ; but  its  principal  ore  is  the  sulphuret  which  is  found  mas- 
sive and  crystallized,  and  of  which  there  are  several  varieties.  The 
most  common  is  the  radiated , which  is  of  a gray  colour  and  brittle. 

This  ore  may  be  decomposed,  and  the  pure  metal  obtained  from  it, 

by  the  following  process  : 

Mix  three  parts  of  the  powdered  sulphuret  with  two  of  crude  tartar,  one  of  ni-  Reduction 
tre,  and  throw  the  mixture  by  spoonfuls  into  a red-hot  crucible ; then  heat  of. 
the  mass  to  redness,  and  a button  will  be  found  at  the  bottom  of  the  crucible, 
which  is  the  metal  as  it  commonly  occurs  in  commerce. 

1114.  The  metal  thus  obtained  is  not  pure  enough  for  chemical 
use,  and  for  that  should  be  procured  by  heating  the  sesquioxide  with 
an  equal  weight  of  cream  of  tartar. 

1115.  Antimony  (sometimes  called  regulus  of  antimony ),  is  of  a Properties, 
silvery  white  colour,  brittle,  and  crystalline- in  its  ordinary  texture. 

It  fuses  at  about  810°  and  is  volatile  at  a high  heat.  Its  specific- 
gravity  is  6.702.  Placed  upon  ignited  charcoal,  under  a current  of 
oxygen  gas,  antimony  burns  with  great  brilliancy. 

The  vapour  of  water,  brought  into  contact  with  ignited  antimony,  Decompo- 
is  decomposed  with  so  much  rapidity  as  to  produce  a series  of  deto-  ses  water, 
nations. 

1116.  Sesquioxide  of  Antimony.  2Sb-|-30,  Sb,  or  Sb203,  129.2  2 Sesquiox- 
eq.  ant.  + 24  3 eq.  oxy.  = 153.2  equiv.  When  sesquichloride  ofide‘ 
antimony,  made  by  boiling  the  native  sulphuret  in  hydrochloric  acid 

(755),  is  poured  into  water,  a white  curdy  precipitate  subsides, 
formerly  called  powder  of  Algarotk , which  consists  of  sesquioxide 


286 


Chap.  IV. 


Properties. 


Solubility 
of  its  salts. 


Detected* 


Antimoni- 
ous  acid, 


Properties. 


Metals — Antimony. 

of  antimony  combined  with  undecomposed  sesquichloride.  On  de- 
composing the  latter  by  digestion  with  carbonate  of  potassa  and  then 
washing  with  water,  the  sesquioxide  is  obtained  in  a state  of  purity. 
It  may  also  be  procured  by  adding  carbonate  of  potassa  or  soda  to  a 
solution  of  tartar  emetic,  and  by  sublimation  during  the  combustion 
of  antimony.  When  slowly  sublimed  it  condenses  in  fine  needles  of 
silvery  whiteness.  It  occurs  as  a mineral,  the  oxide  of  antimony 
of  mineralogists,  the  primary  form  of  which  is  a right  rhombic  prism, 
isomorphous  with  the  crystals  of  arsenious  acid  lately  observed  by 
Wohler.*  (1049.) 

1117.  It  is  a white  powder,  acquiring  a yellow  tint  by  heat.  Sp. 
gr.  5.566.  It  is  volatile  and  may  be  sublimed  ; heated  in  the  air  it 
absorbs  oxygen,  and  antimonious  acid  is  generated. 

1118.  It  is  the  only  oxide  which  forms  regular  salts  with  acids, 
and  is  the  base  of  emetic  tartar , the  tartrate  of  antimony  and  potash. 

Most  of  its  salts  are  either  insoluble  in  water,  or,  like  chloride  of 
antimony,  are  decomposed  by  it,  owing  to  the  affinity  of  that  fluid, 
for  the  acid  being  greater  than  that  of  the  acid  for  sesquioxide  of 
antimony.  This  oxide  is  therefore  a feeble  base,  and  indeed  pos- 
sesses the  property  of  uniting  with  alkalies.  To  the  foregoing  re- 
mark, however,  tartrate  of  antimony  and  potassa,  is  an  exception, 
for  it  dissolves  readily  in  water  without  change.  By  excess  of  tar- 
taric or  hydrochloric  acids,  the  insoluble  salts  of  antimony  may  be 
rendered  soluble  in  water. 

1119.  The  presence  of  antimony  in  solution  is  easily  detected  by 
hydrosulphuric  acid.  This  gas  occasions  an  orange-coloured  preci- 
pitate, hydrated  sesquisulphuret  of  antimony,  which  is  soluble  in 
pure  potassa,  and  is  dissolved  with  disengagement  of  hydrosulphuric 
acid  gas  by  hot  hydrochloric  acid,  forming  a solution  from  which 
the  white  oxychloride  ( poivder  of  Algaroth)  is  precipitated  by 
water. 

In  trying  the  effect  of  reagents  on  solutions  of  sesquioxide  of  an- 
timony, it  is  convenient  to  employ  tartar  emetic,  from  its  property  of 
dissolving  in  pure  water  without  decomposition.  T.  357. 

It  may  be  detected  when  present  even  in  small  quantity  by  de- 
composing antimoniuretted  hydrogen,  in  the  apparatus  (fig.  179,  p. 
274.  )t 

1120.  Antimonious  Acid , 2Sb-|-40,  Sb,  or  Sb204, 129.2  2 eq.  antim. 
+ 32  4 cq.  oxy.  = 161.2  equiv.  When  metallic  antimony  is  di- 
gested in  strong  nitric  acid,  the  metal  is  oxidized  at  the  expense  of 
the  acid,  and  hydrated  antimonic  acid  is  formed  ; on  exposing  this 
substance  to  a red  heat,  it  gives  out  water  and  oxygen  gas,  and  is 
converted  into  antimonious  acid.  It  is  also  generated  when  the 
oxide  is  exposed  to  heat  in  open  vessels. 

1121.  This  acid  is  formed  in  the  process  of  preparing  the  Pulvis 
Antimonialis  of  the  Pharmacopoeia.  Antimonious  acid  is  white 
while  cold,  but  yellow  when  heated,  is  very  infusible,  and  fixed  in 
the  fire,  two  characters  by  which  it  is  readily  distinguished  from  the 

* Ann.  de  C/iim.  et  de  Pkys.  li.  201. 

t For  the  method  of  detecting  antimony  in  mixed  fluids,  &e.,  see  Turner,  p.  357. 
and  Christison  on  Poisons,  354. 


Oxy sulphur et  of  Antimony . 

sesquioxide.  It  is  insoluble  in  water,  and  likewise  in  acids  after 
being1  heated  to  redness.  It  combines  in  definite  proportions  with 
alkalies,  and  its  salts  are  called  antimonites.  Antimonious  acid  is 
precipitated  from  these  salts  by  acids  as  a hydrate. 

1122.  Antimonic  Acid,  2Sb-f-50,  Sb,  or  Sb205,  129.2  2 eq.  antim. 
+ 40  5 eq.  oxy.  = 169.2  equiv.,  sometimes  called  peroxide  of  an- 
timony, is  obtained  as  a white  hydrate,  by  digesting  the  metal  in 
strong  nitric  acid,  or  by  dissolving  it  in  nitro-hydrochloric  acid,  con- 
centrating by  heat  and  throwing  the  solution  into  water.  When  re- 
cently precipitated  it  reddens  litmus,  and  may  be  dissolved  in  water 
by  means  of  hydrochloric  or  tartaric  acid.  It  does  not  enter  into 
definite  combination  with  acids,  but  with  alkalies  forms  salts,  which 
are  called  anlimoniates.  When  hydrated  antimonic  acid  is  exposed 
to  a temperature  of  500°  or  600°  F.,  the  water  is  evolved,  and  the 
anhydrous  acid  of  a yellow  colour  remains  ; exposed  to  a red  heat, 
it  parts  with  oxygen,  and  is  converted  into  antimonious  acid. 

1123.  Chlorides  of  Antimony,  2Sb-f-3Cl  or  Sb2Cl3,  129.2  2 eq. 
antim.  -j-  106.26  3 eq.  chlor.  — 235.46  equiv.  When  antimony  in 
powder  is  thrown  into  a jar  of  chlorine  gas,  combustion  ensues,  and 
the  sesquichloride  of  antimony  is  generated,  (616.)  The  same  corn- 
pound  may  be  formed  by  distilling  a mixture  of  antimony  with 
about  twice  and  a half  its  weight  of  corrosive  sublimate,  when  the 
volatile  sesquichloride  of  antimony  passes  over  into  the  recipient, 
and  metallic  mercury  remains  in  the  retort.  At  common  tempera- 
tures it  is  a soft  solid,  thence  called  butter  of  antimony,  which  is  li- 
quefied by  gentle  heat,  and  crystallizes  on  cooling.  It  deliquesces 
on  exposure  to  the  air.^ 

1124.  Sesquisulphuret  of  Antimony,  2Sb-J~3S,  or  Sb2S3,  129.2  2 
eq.  antim.  -f-  48.3  3 eq.  sulph.  ===  177.5  equiv.  This  is  by  far  the 
most  abundant  ore  of  antimony,  and  is  hence  employed  in  making 
the  preparations  of  antimony.  Though  generally  compact  or  earthy, 
it  sometimes  occurs  in  acicular  crystals  and  in  rhombic  prisms.  Its 
sp.  gr.  is  4.62,  colour  red-gray,  and  its  lustre  metallic.  When  heat- 
ed in  close  vessels,  it  enters  into  fusion  without  any  other  change. 

1125.  It  may  be  formed  artificially  by  fusing  together  antimony 
and  sulphur,  or  by  transmitting  a current  of  hydrosulphuric  acid 
gas  through  a solution  of  tartar  emetic : in  this  case  it  falls  as  a hy- 
drate of  an  orange-red  colour,  and  does  not  acquire  its  dark  colour 
till  its  water  is  expelled  by  heat.f 

1126.  OxysUlphuret  of  Antimony , 2Sb2S3-|_Sb203 , 355  2 eq. 
sesquisulph.  -f-  153.2  1 eq.  sesquiox.  ==;  508.2  equiv.,  occurs  in  the 
mineral  kingdom,  as  the  red  antimony  of  mineralogists.  The  phar- 
maceutic preparations,  known  as  glass , liver  and  crocus  of  antimony, 


* Bichloride  of  Antimony,  2Sb+4Cb  or  Sb2C14;  129.2  2 eq.  antim.  -f  141.68  4 eq. 
chlor.  = 270.88  equiv. 

Per  chloride  of  Antimony,  2Sb-f;5Cl,  or  Sb^Cl5,  129-2  2 eq.  antim.  + 177.1  5 eq. 
chlor.  = 306.3  equiv. 

t Oxychloride  of  Antimony,  2Sb‘2Cl3-f9Sb203,  470.92  2 eq.  sesquichlor.  + 1378.8 
9 eq.  sesquioxide.  = 1849.72  equiv.,  is  obtained  when  an  acid  solution  of  the  ses- 
quichloride is  thrown  into  a large  quantity  of  water  and  the  precipitate  allowed  to 
subside.  It  has  been  lately  examined  by  Johnson,  see  Edin.  Philos.  Jour . No. 
25,  and  hand,  and  Edin.  Philos.  Mag.  No.  40. 


287 


Sect.  VI. 


Antimonic 

acid. 


Chlorides. 


Sesquisul- 

phuret. 


Artificial, 


Oxysul- 

phuret. 


288 


Metals — Antimony. 


Chap.  IV. 


Kermes 

mineral. 


Alloys. 


Type  me- 
tal. 


are  of  a similar  nature,  which  are  made  by  roasting  the  native 
sulphuret,  so  as  to  form  sulphurous  acid  and  sesquioxide  of  antimo- 
ny, and  then  vitrefying  the  oxide  together  with  undecomposed  ore, 
by  means  of  a strong  heat.  The  product  will  of  course  differ  ac- 
cording as  more  or  less  of  the  sulphuret  escapes  oxidation  during 
the  process. 

1127.  When  sesquisulphuret  of  antimony  is  boiled  in  a solution 
of  potassa  or  soda,  a liquid  is  obtained,  from  which  on  cooling  an 
orange-red  matter  called  kermes  mineral  is  deposited ; and  on  neu- 
tralizing the  cold  solution  with  an  acid,  an  additional  quantity  of  a 
similar  substance,  the  golden  sulphuret * of  the  Pharmacopoeia,  sub- 
sides. These  compounds  may  also  be  obtained  by  igniting  sesqui- 
sulphuret of  antimony  with  an  alkali  or  alkaline  carbonate,  and 
treating  the  product  with  hot  water;  or  by  boiling  the  mineral  in  a 
solution  of  carbonate  of  soda  or  potassa. t 

1128.  Antimony  forms  brittle  alloys  with  the  malleable  metals. 
Gold  alloyed  with  its  weight  of  antimony,  is  perfectly  brittle; 
and  even  the  fumes  of  antimony  in  the  vicinity  of  melted  gold  are 
sufficient  to  destroy  its  ductility.  With  potassium  and  sodium  it 
forms  white  brittle  compounds,  destructible  by  the  action  of  air  and 
water. 

An  alloy  with  lead  in  the  proportion  of  3 lead  to  1 antimony,  and 
a small  addition  of  copper,  is  used  for  printers'  types.  With 
lead  only,  a white  and  rather  brittle  compound  is  formed,  used  for 
the  plates  upon  which  music  is  engraved.  With  iron  it  forms  a 
hard  whitish  alloy,  formerly  called  martial  regulus , which  may  be 
obtained  by  fusing  two  parts  of  sulphuret  of  antimony  with  one  of 
iron  filings ; a scoria  consisting  chiefly  of  sulphuret  of  iron  is  formed ; 
and  the  fused  alloy  beneath  usually  presents  a stellated  appearance 
in  consequence  of  its  crystallization.  This  star  was  much  admired 
by  the  alchymists,  who  considered  it  a mysterious  guide  to  transmu- 
tation. With  tin,  antimony  constitutes  a kind  of  pewter , a term, 
however,  which  has  also  been  applied  to  some  other  alloys,  espe- 
cially that  of  lead  and  tin.  The  finest  pewter  consists  of  about  12 
parts  of  tin  and  1 of  antimony,  with  a small  addition  of  copper.  A 
good  white  metal,  used  for  teapots,  is  composed  of  100  tin,  8 anti- 
mony, 2 bismuth,  and  2 copper 


* Antimonii  sulphuretum  precipitatum,  U.  S.  P. 

+ Great  difference  of  opinion  has  long  existed  as  to  the  nature  of  kermes.  See 
Turner,  359. 

The  finest  kermes  is  obtained,  according  to  Cluzel,  from  a mixture  of  4 parts  of 
sulphuret  of  antimony,  90  of  crystallized  carbonate  of  soda,  and  1000  of  water. 
These  materials  are  boiled  for  half  or  three-quarters  of  an  hour;  the  hot  solution  is 
filtered  into  a warm  vessel,  in  order  that  it  may  cool  slowly;  and  after  24  hours,  the 
deposite  is  collected  on  a filter,  moderately  washed  with  cold  water,  and  dried  at  a 
temperature  of  70°  or  30°  F. 

Bisulphuret  of  Antimony,  2Sb+4S,  or  Sb^S4,  129.2  2 eq.  antim.  +64.4  4 eq.  sulph. 
= 193.6  equiv. 

Persulpkuret  of  Antimony,  2Sb+5S,  or  Sb2S5,  129.2  2 eq.  antim.+  80.5  5 eq.  sulph. 
= 209.7  equiv. 


Uranium — Cerium . 


289 


Uranium.  s-ech.yV. 

Symb.  U Eq.  217 

i 129.  This  metal  was  discovered  by  Klaproth  in  1789,*  in  a min-  Uranium, 
eral  called  pitch-blende,  which  consists  of  protoxide  of  uranium  and 
oxide  of  iron. 

The  metal  is  procured  by  heating  the  ore  to  redness,  digesting  its  Process, 
powder  in  pure  nitric  acid  diluted  with  3 or  4 parts  of  water  ; lead 
and  copper  are  separated  by  hydrosulphuric  acid  gas ; the  solution 
is  concentrated  and  set  aside  when  nitrate  of  sesquioxide  of  uranium 
crystallizes  in  prisms  of  a lemon  yellow  colour. 

1130.  The  properties  of  uranium  are  not  well  known;  its  sp.  gr.  Properties, 
is  9.f 

1131.  Protoxide  of  Uranium , U+O,  U,  or  Uo,  217  1 eq.  uran.  Protoxide. 
-J-  8 1 eq.  oxy.  = 225  equiv.,  is  of  a dark  green  colour,  and  is  ob- 
tained by  decomposing  the  nitrate  of  the  sesquioxide  by  heat.  It  is 
exceedingly  infusible,  unites  with  acids,  forming  salts  of  a green 
colour,  and  is  readily  oxidized  by  nitric  acid. 

The  protoxide  is  employed  in  the  arts  for  giving  a black  colour  Use- 
to  porcelain. 

1132.  Sesquioxide  of  Uranium , 2U-j-30,  U,  or  U203,  434  2 eq.  S^quiox- 
uran.  -j-  24  3 eq.  oxy.  = 458  equiv.,  is  of  a yellow  colour,  and1  e‘ 
most  of  its  salts  have  the  same.  It  combines  with  acids,  and  with 
alkaline  bases.  From  the  former  it  is  precipitated  as  a yellow  hy- 
drate by  the  pure  alkalies. 

Cerium. 


Symb.  Ce  Eq.  46 

1133.  This  metal  was  obtained  by  Hisinger  and  Berzelius,  fromCerium> 
a mineral  found  at  Bastnas  in  Sweden,  to  which  they  have  given  the  ores' 
name  of  Cerite.%  It  is  also  contained  in  Allanite , a mineral  from 
Greenland,  first  distinguished  as  a peculiar  species  by  Allan,  of 
Edinburgh.  It  contains,  according  to  Thomson’s  analysis,  about  40 

per  cent,  of  oxide  of  cerium. 

This  oxide  is  extremely  difficult  of  reduction.  Children  succeeded 
in  fusing  it  by  the  aid  of  his  powerful  Voltaic  apparatus,  and  when 
intensely  heated  it  burned  with  a vivid  flame,  and  was  partly  vol- 
atilized. 

1134.  The  attempts  of  Vauquelin  to  reduce  the  oxide  of  cerium  Vauque- 
produced  only  a small  metallic  globule,  not  larger  than  a pin’s  r/ment?6" 
head.  This  globule  was  not  acted  upon  by  any  of  the  simple  acids  ; 

but  it  was  dissolved,  though  slowly,  by  nitro-hydrochloric  acid. 

1135.  Protoxide  of  Cerium,  Ce-[-0,  Ce,  or  CeO,  46  1 eq.  cerium,  protoxide. 
+ 8 1 eq.  oxy.  = 54  equm  This  oxide  is  a white  powder,  inso- 
luble in  water,  forming  salts  with  acids,  all  of  which,  if  soluble, 


* Named  after  the  new  planet,  discovered  in  that  year  and  called  Uranus. 

+ Buchholz,  in  Mem.  Acad.  Sci.  of  Stockholm,  1S22. 

t The  name  Cerium  was  given  to  this  metal  from  the  planet  Ceres , discovered 
about  the  same  period.  See  Nicholson’s  Jour.  xii.  105. 

37 


290 


Metals — Bismuth. 


Chap.  IV.  - 


Sesquiox- 

ide. 


Native. 


Properties. 


Process  for 

obtaining 

crystals. 


Oxide. 


Protoxide. 


Magistery. 


have  an  acid  reaction.  Heated  in  open  vessels,  it  absorbs  oxygen, 
and  is  converted  into  the  sesquioxide.  It  is  precipitated  as  a white 
hydrate  by  pure  alkalies  ; as  a white  carbonate  by  alkaline  carbo- 
nates, but  is  redissolved  by  the  precipitant  in  excess  ; and  as  a white 
oxalate  by  oxalate  of  ammonia. 

1136.  Sesquioxide  of  Cerium , 2Ce-|-30,  Ce,  or  Ce203,  92  2 eq. 
cerium,  — (—  24  3 eq.  oxy.  = 116  equiv.,  has  a fawn  red  colour  ; it  is 
dissolved  by  several  of  the  acids,  but  is  a weaker  base  than  the  pro- 
toxide. Digested  in  hydrochloric  acid,  chlorine  is  disengaged  and 
a protochloride  results.  It  is  most  readily  extracted  from  cerite  by 
a process  of  Laugier.* 

Bismuth. 

Symb.  Bi  Eq.  71 

1137.  This  metal  is  found  native;  combined  with  oxygen;  and 
with  arsenic  and  sulphur.  Native  Bismuth  occurs  crystallized  in 
octohedra  and  cubes,  and  in  addition  to  arsenic  generally  contains 
cobalt. 

1138.  Bismuth  has  a reddish  white  colour,  and  is  composed  of 
broad  brilliant  plates  adhering  to  each  other.  Its  sp.  gr.  is  9.822, 
but  is  increased  by  hammering.  It  breaks,  however,  under  the 
hammer,  and  hence  cannot  be  considered  as  malleable ; nor  can  it 
be  drawn  out  into  wire.  The  bismuth  of  commerce  is  not  quite 
pure. 

1139.  Bismuth  is  one  of  the  most  fusible  metals,  melting  at  476° 
F.,  and  it  forms  more  readily  than  most  other  metals,  distinct  crys- 
tals by  slow  cooling. 

It  may  be  obtained  in  regular  crystals,  by  fusing  a quantity  of  it 
in  a crucible,  and  allowing  it  to  cool  till  a crust  is  formed  on  the 
surface  ; the  extremity  of  the  crucible  may  then  be  broken  off,  and 
the  fluid  metal  beneath  be  allowed  to  escape.  The  under  surface 
of  the  crust  will  be  found  beautifully  crystallized. 

1140.  When  bismuth  is  exposed  to  heat  and  air  it  oxidizes.  If 
the  heat  be  increased  by  directing  a current  of  oxygen  upon  the 
metal,  it  burns  with  much  brilliancy,  and  produces  abundant  yellow 
fumes  of  protoxide.  It  is  readily  oxidized  and  dissolved  by  nitric 
acid. 

1141.  Protoxide  of  Bismuth , Bi— [-0,  Bi,  or  BiO,  71  1 eq.  bism. 
— |—  8 1 eq.  oxy.  = 79  equiv.  This  compound  is  readily  prepared 
by  heating  to  redness  the  nitrate  or  subnitrate  of  protoxide  of  bis- 
muth. Its  colour  is  yellow ; at  a full  red  heat  it  is  fused  into  a 
brown  liquid,  which  on  cooling  becomes  a yellow  transparent  glass 
of  sp.  gr.  8.211.  At  intense  temperatures  it  is  sublimed.  It  unites 
with  acids,  and  most  of  its  salts  are  white. 

1142.  When  nitrate  of  protoxide  of  bismuth,  either  in  solution 
or  in  crystals,  is  put  into  water,  a copious  precipitate,  the  subnitrate, 
of  a beautifully  white  colour,  subsides,  which  was  formerly  called 


* For  which  see  Turner’s  Chem.  362. 


Titanium. 


291 


the  magistery  of  bismuth  and  rpearl  white.  From  its  whiteness  it  is  Sect,  v-i. 
sometimes  employed  as  a paint  for  improving  the  complexion.* 

If  the  nitrate  with  which  it  is  made  contains  no  excess  of  acid,  white  ox- 
and  a large  quantity  of  water  is  employed,  nearly  the  whole  of  the  i(*e. 
bismuth  is  separated  as  a subnitrate,  White  oxide  of  the  Pharmaco- 
poeia. By  this  character  bismuth  may  be  both  distinguished  and 
separated  from  other  metals, 

1143.  Sesquioxide  of  Bismuth , 2Bi-|-30j  Bi,  or  Bi203,  142  2Sesquiox= 
eq.  bism.  24  3 eq.  oxy.  = 166  equiv.  This  oxide  is  generated 

when  hydrate  of  potassa  is  fused  at  a moderate  heat  with  protoxide 
of  bismuth  ; but  the  best  mode  of  preparation  is  first  to  prepare  the 
protoxide  by  igniting  the  subnitrate,  and  then  gently  heating  it  for 
some  time  in  a solution  of  chloride  of  potassa  or  soda.  After  wash- 
ing with  water,  any  unchanged  protoxide  is  dissolved  by  a solution 
made  with  1 part  of  nitric  acid  (quite  free  from  nitrous  acid)  and  9 
of  water. 

1144.  As  thus  prepared,  sesquioxide  of  bismuth  is  a heavy  powder  Properties, 
of  a brown  colour,  with  little  disposition  to  unite  either  with  acids 

or  alkalies.  Heated  with  sulphuric  or  phosphoric  acid,  it  gives  off 
oxygen  gas,  and  with  hydrochloric  acid,  chlorine  is  evolved,  and  the 
protochloride  produced.! 

1145.  Chloride  of  Bismuth , Bi— j— Cl , or  BiCl,  71  1 eq.  bism. -j- Chloride. 
35.42  1 eq.  chlor.  — 106,42  equiv.  When  bismuth  in  fine  powder 

is  introduced  into  chlorine  gas,  it  takes  fire,  burns  with  a pale  blue 
light,  and  is  converted  into  a chloride,  formerly  termed  butter  of  bis- 
muth. It  may  be  prepared  conveniently  by  heating  two  parts  of 
corrosive  sublimate  with  one  of  bismuth,  and  afterwards  expelling 
the  excess  of  the  former,  together  with  the  metallic  mercury  by 
heat. 

1146.  Chloride  of  bismuth  is  of  a grayish-white  colour,  opaque,  properties, 
and  of  a granular  texture.  It  fuses  at  a temperature  a little  above 

that  at  which  the  metal  itself  is  liquefied,  and  bears  a red  heat  in 
close  vessels  without  subliming. 

1147.  Bismuth  also  combines  with  bromine,  and  with  sulphur, 
the  sulphuret  is  found  native. 

Titanium.% 

Symb.  Ti  Eq.  24.3 

1148.  Titanium,  in  the  metallic  state,  was  discovered  by  Wollas-  £)jscovery# 
ton  in  1822,  in  the  slag  at  the  bottom  of  an  iron  smelting-furnace  in 

South  Wales. § It  has  been  since  found  in  several  other  places  in 
Europe.  It  has  the  form  of  small  smooth  cubes,  having  a red  col- 
cur  exceedingly  similar  to  that  of  copper.  The  cubes  are  hard 
enough  to  scratch  rock  crystal,  and  cannot  be  fused  by  the  highest 
temperature  which  can  be  raised  by  the  blow-pipe.  The  sp.  gr.  is 


* If  a small  portion  of  hydrochloric  acid  be  mixed  with  the  nitric,  and  the  preci- 
pitate be  washed  with  but  a small  quantity  of  cold  water,  it  will  appear  in  minute 
scales,  constituting  th q pearl-powder  of  perfumers  ; but  it  is  an  inconvenient  pigment, 
owing  to  the  facility  with  which  it  is  blackened  by  hydrosulphuric  acid, 
t An.  de  Ch.  et  de  Pfi.  li.  267. 

t Named  by  Klaproth  after  the  Titans  of  ancient  fable.  § Philos.  Trans.  1823. 


292 


Metals — Titanium. 


[Chap.  IV. 


Prepared. 


Oxide. 


Prepared. 


Titanic 

acid. 


Process. 


Properties. 


Solubility, 

&c. 


5.3.^  It  does  not  appear,  however,  to  be  absolutely  free  from  iron. 
Wollaston  found  that  when  suspended  by  a fine  thread  a magnu 
drew  it  about  20  degrees  from  the  perpendicular.  He  succeeded  in 
detecting  the  presence  of  iron  in  it,  and  calculated  the  amount  of 
that  metal  at  part  of  the  weight  of  the  titanium. f 

1 149.  Metallic  Titanium  may  be  obtained  by  putting  fragments 
of  recently  made  chloride  of  titanium  and  ammonia  into  a glass  tube 
half  an  inch  wide  and  two  or  three  feet  long,  transmitting  through 
it  a current  of  perfectly  dry  ammonia,  and,  when  atmospheric  air 
is  entirely  displaced,  applying  heat  until  the  glass  softens.  Com- 
plete decomposition  ensues,  nitrogen  gas  is  disengaged,  hydrochlo- 
rate of  ammonia  sublimes,  and  metallic  titanium  is  left  in  the  state 
of  a deep  blue-coloured  powder.  If  exposed  to  the  air  while  warm, 
is  apt  to  take  fire. 

11*50.  Oxide  of  Titanium , (probably)  Ti— |— 0,  or  TiO,  24.3  1 eq. 
titan,  -f  8 1 eq.  oxy.  = 32.3  equiv.,  is  prepared  by  exposing  titanic 
acid  to  a strong  heat  in  a black  lead  crucible  ; the  exterior  of  the 
mass  obtained  consists  of  metallic  titanium,  the  interior  is  supposed 
to  be  the  oxide.  It  may  be  formed  in  the  moist  way  by  acting  upon 
a solution  of  titanic  acid  in  hydrochloric  acid  by  zinc  or  iron.  The 
titanic  acid  is  thrown  down  as  a purple  powder,  but  cannot  be  col- 
lected. 

1 151.  Titanic  Acid , or  Peroxide  of  Titanium , Ti-|-20,  Ti,  or  TiO2, 
24.3  1 eq.  titan.  -f-  16  2 eq.  oxy.  ==  40.3  equiv.,  occurs  nearly  pure 
in  the  minerals  anatase  and  rutile;  it  exists  also  in  several  other 
minerals. 

It  may  be  obtained  from  rutile,  or  titaniferous  iron  exposed  in  a porcelain 
tube  to  a very  strong  red  heat  and  a current  of  hydrosulphuric  acid  gas,  which  gives 
rise  to  water  and  sulphuret  of  iron.  When  the  water  ceases  to  appear,  the  mass 
is  removed  and  digested  in  hydrochloric  acid  to  remove  the  iron,  and  the  titanic 
acid  is  separated  from  adhering  sulphur  by  heat.* 

1152.  Titanic  acid  is  quite  white,  exceedingly  infusible  and  diffi- 
cult of  reduction  ; after  being  once  ignited  it  ceases  to  be  soluble  in 
acids,  except  in  the  hydrofluoric.  In  its  chemical  relations  it  is  ana- 
logous to  silicic  acid,  being  a feeble  acid,  but  combining  with  metal- 
lic oxides.  In  the  state  of  hydrate,  it  has  a singular  tendency  to 
pass  through  the  pores  of  a filter  when  washed  with  pure  water ; but 
the  presence  of  a little  acid,  alkali,  or  a salt,  prevents  this  inconve- 
nience. 

1153.  If  previously  ignited  with  carbonate  of  potassa,  titanic  acid 
is  soluble  in  dilute  hydrochloric  acid  ; but  it  is  retained  in  solution 
by  so  feeble  an  attraction,  that  it  is  precipitated  merely  by  boiling.  It 
is  likewise  thrown  down  by  the  pure  and  carbonated  alkalies,  both 
fixed  and  volatile.  A solution  of  gall-nuts  causes  an  orange-red  co- 
lour, which  is  very  characteristic  of  titanic  acid.  When  a rod  of 
zinc  is  suspended  in  the  solution,  a purple-coloured  powder,  probably 
the  oxide,  is  precipitated,  which  is  gradually  converted  into  titanic 
acid. 


* From  the  extreme  infusibility  of  the  cubes  of  metallic  titanium,  Wollaston  infers 
that  they  have  not  been  formed  by  crystallization  in  cooling  from  a state  of  fusion  ; 
but  from  the  reduction  of  the  oxide  dissolved  in  the  slag  around  them, 
t Phil.  Trans,  p.  200.  Thomson’s  First  Prindp.  2.  80. 
tRose,  An.  de  Ch.  et  de  Ph.  xxiii.  and  xxxviii.  ] 31 . 


Tellurium * 


293 


1154.  Bichloride  of  Titanium.  Ti-f-2Cl,  or  TiCl2,  24.3  1 eq.  geCt.  vi. 
titan.  + 70.S4  2 eq.  chlor.  = 95.14  equiv.  This  substance  was  Bichloride, 
discovered  in  the  year  1824  by  transmitting  dry  chlorine  gas  over 
metallic  titanium  at  a red  heat. 

1155.  At  common  temperatures  it  is  a transparent  colourless  fluid  Properties, 
of  considerable  specific  gravity,  boils  violently  at  a temperature  a 

little  above  212°,  and  condenses  again  without  change.  Dumas  has 
shown  that  the  density  of  its  vapour  may  be  estimated  at  6.615.  In 
open  vessels  it  is  attacked  by  the  moisture  of  the  atmosphere,  and 
emits  dense  white  fumes  of  a pungent  odour  similar  to  that  of  chlo- 
rine, but  not  so  offensive.  On  adding  a few  drops  of  water  to  a few 
drops  of  the  liquid,  combination  ensues  with  almost  explosive  vio- 
lence, from  the  evolution  of  intense  heat;  and  if  the  water  is  not  in 
excess  a solid  hydrate  is  obtained.  On  exposure,  and  on  adding 
water,  the  greater  part  is  dissolved. 

Tellurium. 

Symb.  Te  Equiv.  64.2 

1156.  Tellurium  is  a rare  metal,  found  in  the  gold  mines  of  Tran-  Discovery. 
sylvania,and  in  Connecticut,  U.  S in  small  quantity.  Its  existence 

was  inferred  by  Muller  in  the  year  1782,  and  fully  established  in 
1798  by  Klaproth,  who  gave  it  the  name  of  tellurium , from  tellies, 
the  earth , suggested  by  the  source  from  which  he  drew  the  name  of 
uranium.!  It  occurs  in  the  metallic  state,  chiefly  in  combination 
with  gold  and  silver. 

1157.  Tellurium  is  of  a bright  gray  colour,  brittle,  easily  fusible,  Properties 
and  very  volatile.  Its  specific  gravity  is  6.17. 

1158.  It  is  oxidized  when  heated  in  contact  with  the  air ; and  Oxide, 
burns  with  a sky-blue  flame,  edged  with  green.  Upon  charcoal, 
before  the  blow-pipe,  it  inflames  with  a violence  resembling  detona- 
tion ; exhibits  a vivid  flame ; and  entirely  flies  off  in  a gray  smoke, 
having  a peculiarly  nauseous  smell.!  This  smoke,  when  condensed, 

and  examined  in  quantity,  is  found  to  be  white  with  a tint  of  yellow. 

It  is  fusible  by  a strong  heat,  and  volatile  at  still  higher  temperature. 

1159.  Tellurous  Acid.  Te-f-20,  Te,  or  TeO2,  64.2  1 eq.  tellur. 

-|-  16  2 eq.  oxy.  '=  80.2  equiv.  This  compound,  also  called  oxide  q/Tellurous 
tellurium,  is  generated  by  the  action  of  nitric  acid  on  tellurium,  by  acid- 
which  acid  it  is  dissolved ; but  the  solution  possesses  such  little  per- 
manence that  mere  affusion  of  water  precipitates  part  of  it,  and  the 
rest  is  obtained  by  evaporating  to  dryness.  In  this  state,  it  is  a 
white  granular  anhydrous  powder,  which  slowly  reddens  moist  lit- 
mus paper. 

1160.  Its  aqueous  solution  reddens  litmus  paper ; it  becomes  tur- 
bid at  68°,  and  the  acid  which  falls  is  no  longer  soluble  in  acids.  Properties. 
In  these  properties  tellurous  acid  closely  resembles  the  titanic 

and  several  other  feeble  acids,  which  have  a soluble  hydrated 
state  easily  convertible  into  an  insoluble  anhydrous  one.  Its 
salts  are  precipitated  black  by  hydrosulphuric  acid,  bisulphuret  of 
tellurium  being  formed. § 

* Amer.  Jour.  i.  405.  + Contributions,  iii. 

t Ascribed  by  Berzelius  to  the  presence  of  selenium. 

§ Hydrotelluric  Acid.  Te+H,  or  TeH,  64.2  1 eq.  tellur.  + l l eq.  hyd.  — 65.2 


294 


Chap  IV. 


Ores  of 
copper ; 
Native 
copper. 


Meta)  ob- 
tained pure. 


Properties. 


Action  of 
air. 


Combus- 
tion of  cop- 
per. 

Exp. 


Effect  of 
heat. 


Equivalent. 


Metals — Copper . 

Copper. 

Symb.  Cu  Equiv.  31.6 

1161.  This  metal  was  known  in  the  early  ages  of  the  world,  and 
was  the  principal  ingredient  in  domestic  utensils,  and  in  the  instru- 
ments of  war,  previous  to  the  discovery  of  malleable  iron.* *  It  is 
found  native,  and  in  various  states  of  combination.  Native  copper 
is  by  no  means  uncommon,  being  found  more  or  less  in  most  copper 
mines.  It  occurs  in  a variety  of  forms;  massive,  dendritic,  granu- 
lar. and  crystallized  in  cubes,  octohedra,  &c.  It  is  found  in  Corn- 
wall, Siberia,  and  other  parts  of  Europe.  Large  masses  have  been 
found  in  various  parts  of  America ; one  of  which,  about  30  miles  from 
Lake  Superior,  described  by  Schoolcraft,  weighs  hy  estimation  2000 
lbs.t  The  copper  of  commerce  is  extracted  chiefly  from  the  native 
sulphuret ; especially  from  copper  pyrites,  a double  sulphuret  of  iron 
and  copper. 

1162.  The  metal  may  be  obtained  by  dissolving  the  copper  of 
commerce  in  hydrochloric  acid  ; the  solution  is  diluted  and  a plate  of 
iron  immersed,  upon  which  the  copper  is  precipitated.  It  may  be 
fused  into  a button,  after  having  been  previously  washed  in  dilute 
sulphuric  acid  to  separate  a little  iron  that  adheres  to  it. 

1163.  Copper  has  a fine  red  colour,  and  much  brilliancy ; it  is 
very  malleable  and  ductile,  and  has  a peculiar  smell  when  warmed 
or  rubbed.  It  melts  at  a cherry-red  or  dull  white  heat,  1996°  F. 
Its  sp.  gr.  varies,  being  increased  by  hammering ; when  fused,  its 
density  is  8.S95.  Under  a flame  urged  by  oxygen  gas,  it  takes  fire, 
and  burus  with  a beautiful  green  light. 

1164.  Copper  is  oxidized  by  air.  This  may  be  shown  by  heating 
one  end  of  a polished  bar  of  copper,  which  will  exhibit  various  shades 
of  colour,  according  to  the  intensity  of  the  heat. 

It  burns  with  great  splendour  before  the  compound  blow-pipe, 
upon  charcoal. 

The  white-hot  globule  being  thrown  from  the  charcoal  into  a tall 
jar  or  wide  tube  filled  with  water,  it  will  pass  in  full  ignition,  through 
a column  of  the  fluid  two  feet  high,  and  will  remain  for  some 
time  ignited  on  the  bottom,  which  should  be  protected  by  a layer  of 
sand-I 

A plate  of  copper,  exposed  for  some  time  to  heat,  becomes  covered 
with  protoxide,  which  breaks  off  in  scales  when  the  copper  is  ham- 
mered. 

1165.  From  the  experiments  of  Berzelius,  eight  parts  of  oxygen 
unite  with  31.6  parts  of  copper  to  constitute  the  black  oxide,  and 
therefore  if  this  oxide  be  formed  of  an  atom  of  oxygen  united  with 
an  atom  of  copper  the  eq.  of  this  metal  will  be  31.6.  This  is  adopted 

equiv.  By  acting  on  an  alloy  of  tellurium  with  zinc  or  tin,  by  hydrochloric  acid,  Davy 
discovered  this  gas  in  1809.  It  has  the  properties  of  a feeble  acid. 

Telluric  Acid , Te+30.  Te,  or  Te03,  64-2  1 eq.  tellur,  -j-  24  3 eq.  oxy.  =88.2  equiv. 
For  other  compounds  of  tellurium  see  Turner,  368.  See  also  Berzelius  on  Tellurium , 
in  Ann.  des  Mines,  v.  381,  and  Arner.  Jour,  xxviii.  137. 

* The  word  copper  is  derived  from  the  island  of  Cyprus,  where  it  was  first  wrought 
by  the  Greeks. 

t Stromeyer  has  lately  discovered  it  in  several  specimens  of  meteoric  iron,  but  in  a 
quantity  not  exceeding  of  the  mass.  See  other  localities  in  Cleaveland’s  Mi- 
neralogy, p.  554,  and  J.  D.  Dana’s  System.  X Silliman. 


295 


Protoxide  of  Copper. 

by  many  chemists,  others  regard  it  as  a binoxide,  and  the  red  as  the  Sect,  vi. 
protoxide,  and  take  twice  31.6,  or  63.2,  as  the  eq.  of  copper. 

1166.  Red , or  Dioxide  of  Copper , 2Cu-|-0,  or  Cu20,  63.2  2 eq.  Red  oxide. 
:opper  + 8 1 eq.  oxy.  = 71.2  equiv.,  occurs  native  in  the  form  of 
Dctohedral  crystals,  and  is  found  of  peculiar  beauty  in  the  mines  of 
Cornwall,  it  may  be  prepared  artificially  by  heating,  in  a covered 
crucible,  a mixture  of  31.6  parts  of  copper  filings  with  39.6  of  the 

black  oxide ; or,  still  better,  by  arranging  thin  copper  plates  one 
above  the  other,  with  interposed  strata  of  the  black  oxide,  and  ex- 
posing them  to  a red  heat  carefully  protected  from  the  air.  Another  Process, 
method  is  by  boiling  a solution  of  acetate  of  protoxide  of  copper 
with  sugar,  when  the  dioxide  subsides  as  a red  powder  ; and  another 
is  to  fuse  at  a low  red  heat  the  dichloride  of  copper  with  about  an 
equal  weight  of  carbonate  or  bicarbonate  of  soda,  subsequently  dis- 
solving the  sea-salt  by  water,  and  drying  the  red  powder.* 

In  this  case,  by  an  interchange  of  elements, 

1 eq.  dichloride  of  copper  2Cu-f-Cl  2 1 eq.  red  oxide  . . 2Cu-f-0  Theory, 

and  1 eq.  soda  . . Na-f-O  and  1 eq.  chloride  of  sodium  Na-j-Ci 

1167.  The  red  or  dioxide  of  copper  has  a density  of  6.093,  and  in  properties, 
colour  is  very  similar  to  copper.  At  a red  heat  it  absorbs  oxygen, 

and  is  converted  into  the  protoxide.  Dilute  acids  act  on  it  very 
slowly ; resolving  it  into  metal  and  a protoxide. 

1168.  With  strong  nitric  acid  it  is  oxidized,  binoxide  of  nitrogen  Action  of 
escapes,  and  a nitrate  of  the  black  oxide  is  formed.  Strong  hydro-  acids, 
chloric  acid  forms  with  it  a colourless  solution.  The  red  oxide  of 
copper  is  soluble  in  ammonia,  and  the  solution  is  quite  colourless  ; 

but  it  becomes  blue  with  surprising  rapidity  by  free  exposure  to  air, 
owing  to  the  formation  of  the  black  oxide. 

Put  a small  quantity  of  this  oxide  into  a small  bottle,  nearly  full  of  water  of' 
ammonia,  and  shake  it  frequently,  the  solution  will  have  a rich  blue  colour.  If  ^XP* 
a quantity  of  copper  filings  be  added  and  the  bottle  well  closed  so  as  completely 
to  exclude  the  air,  the  solution  will  become  colourless  in  a few  days.  If  the  cork 
be  withdrawn,  the  blue  colour  will  again  return  as  oxygen  is  absorbed. 

1169.  Black  or  Protoxide.  Cu-j-O,  Cu,  or  CuO,  31.6  1 eq.  cop.  Biack 
-f  8 1 eq.  oxy.  = 39.6  equiv.  This  oxide  of  copper  occurs  na- 
tive, by  the  spontaneous  oxidation  of  other  ores  of  copper ; it  is  the 
copper  black  of  mineralogy. 

1170.  It  may  be  prepared  artificially  by  calcining  metallic  copper,  Artificial, 
by  precipitation  from  the  salts  of  copper  by  means  of  pure  potassa, 

and  by  heating  nitrate  of  copper  to  redness. 

1171.  It  varies  in  colour  from  a dark  brown  to  a bluish-black,  ac-  Properties, 
cording  to  the  mode  of  formation,  and  its  density  is  6.401.  It  under- 
goes no  change  by  heat  alone,  but  is  readily  reduced  to  the  metallic 

state  by  heat  and  combustible  matter.  It  is  insoluble  in  water.  It 
combines  with  nearly  all  the  acids,  and  most  of  its  salts  have  a green 
or  blue  tint.  With  ammonia,  it  forms  a deep  blue  solution,  by 
which  it  is  distinguished  from  all  other  substances. 


* The  following  process  is  recommended  by  Malaguti : 109  parts  of  sulphate  of  cop-  Maiaguti\ 
per  and  57  of  carbonate  of  soda,  both  in  crystals,  are  fused  with  a gentle  heat  j and  the  process- 
mass  left,  when  all  water  is  expelled,  is  pulverized  and  mixed  with  25  parts  of  copper 
filings.  The  mixture  is  pressed  into  a crucible  and  exposed  for  twenty  minutes  to  a 
white  heat.  The  result  is  again  pulverized  and  washed.  .Ann.  de  Chim.  et  de  Phys. 
liv.  216. 


296 


Chap.  IV. 

Salts  recog- 
nised. 


Antidote. 

Metal  sepa- 
rated. 

Detected. 

Dichloride. 


Properties. 


Sulphurets. 


Disulpbu- 
ret  formed. 


Metals — Copper. 

1172.  Its  salts  are  distinguished  from  most  substances  by  their 
colour,  and  are  easily  recognised  by  reagents.  Pure  ammonia 
throws  down  the  disulphate  when  carefully  added ; but  an  excess  of 
the  alkali  instantly  redissolves  the  precipitate,  and  forms  a deep  blue 
solution.  Alkaline  carbonates  cause  a bluish-green  precipitate.  It 
is  precipitated  as  a dark  brown  sulphuret  by  hydrosulphuric  acid, 
and  as  a reddish-brown  ferrocyanuret  by  ferrocyanuret  of  potassium. 

1173.  It  is  thrown  down  of  a yellowish  white  colour  by  albumen, 
and  Orfila  has  proved  that  this  compound  is  inert,  so  that  albumen 
is  an  antidote  to  poisoning  by  copper.* 

1174.  Copper  is  separated  in  the  metallic  state  by  a rod  of  iron  or 
zinc.  The  copper  thus  obtained,  after  being  digested  in  a dilute  so- 
lution of  hydrochloric  acid,  is  almost  chemically  pure. 

1175.  The  best  mode  of  detecting  copper,  when  supposed  to  be 
present  in  mixed  fluids,  is  by  hydrosulphuric  acid.  The  sulphuret, 
after  being  collected,  and  heated  to  redness  in  order  to  char  organic 
matter,  should  be  placed  on  a piece  of  porcelain,  and  be  digested  in 
a few  drops  of  nitric  acid.  Sulphate  of  protoxide  of  copper  is  formed, 
which,  when  evaporated  to  dryness,  strikes  the  characteristic  deep 
blue  tint  on  the  addition  of  ammonia.! 

1176.  Bichloride  of  Copper.  2Cu+Cl,  or  Cu2Cl,  63.2  2 eq. 
copper  -f-  35.42  l eq.  chlor.  = 98.62  equiv.  When  copper  filings 
are  introduced  into  an  atmosphere  of  chlorine  gas,  the  metal  takes 
fire  spontaneously,  and  both  the  chlorides  are  generated.  The  di- 
chloride may  be  conveniently  prepared  by  heating  copper  filings  with 
twice  their  weight  of  corrosive  sublimate.  It  is  slowly  deposited  in 
crystalline  grains,  when  the  green  solution  of  protochloride  of  copper 
is  kept  in  a corked  bottle  in  contact  with  metallic  copper. 

1 177.  The  dichloride  of  copper  is  fusible  at  a heat  just  below  red- 
ness, and  bears  a red  heat  in  close  vessels  without  subliming.  It  is 
insoluble  in  water,  but  dissolves  in  hydrochloric  acid.  Its  colour  va- 
ries with  the  mode  of  preparation,  being  white,  yellow,  or  dark 
brown. t 

1178.  Sulphurets  of  Copper.  The  disvlphur ety  2Cu+S,  orCu2S, 

63.2  2 eq.  copper  4-  16.1  1 eq.  sulph.  — 79.3  equiv.,  is  a natural 
production,  the  copper  glance  of  mineralogists,  and  in  combination 
with  protosulphuret  of  iron,  it  is  a constituent  of  variegated  copper 
ore.$ 

1179.  It  is  formed  by  heating  copper  filings  with  a third  of  their 
weight  of  sulphur;  when  the  sulphur  is  raised  a little  above  its  melt- 

* Superoxide  of  Copper.  Cu+20,  Cu,  or  CuO2,  31.6  1 eq.  cop.  + 16  2 eq.  oxy.  = 
47.6  equiv. 

+ The  action  of  ammonia  may  he  taken  advantage  of  in  cleaning  (or  colouring,  as 
it  is  termed  by  jewellers)  gold  trinkets,  such  as  chains,  &c.  which  are  often  made  of  a 
very  inferior  alloy.  Artists  make  use  of  weak  nitric  acid,  or  of  the  materials  from 
which  the  acid  is  produced,  and  which  often  destroys  the  finer  kinds  of  workmanship 
by  dissolving  the  copper  of  the  alloy  to  some  depth  on  the  surface ; the  gold  not  being 
acted  upon,  the  trinket  appears  as  if  newly  gilded.  Boiling  in  ammonia  is  a safe  sub- 
stitute for  this  process,  and  the  operation  may  be  performed  by  any  person  without 
the  assistance  of  the  artist.  Brewster’s  Jour.  i.  75  ; Bost.  Jour.  ii.  206. 

t Protochloride  of  Copper.  Cu+Cl,  31.6  1 eq.  copper  + 35.42  1 eq.  chlor.  = 

67.02  equiv. 

t For  an  outline  of  the  process  of  reducing  the  ores  of  copper,  see  Brande,  ii.  67, 
and  Vivian,  in  Ann.  Philos.  N.  S.  v.  113. 


297 


Jliloys  of  Copper. 

ing  point,  combustion  suddenly  pervades  the  whole  mass.  The  ex-  Sect,  vl 
pertinent  succeeds  equally  well  in  vacuo  or  in  azote,  u.  370.  Copper 
leaf  burns  in  gaseous  sulphur  as  brilliantly  as  iron  wire  in  oxygen 
gas.* * * § 

1180.  Many  of  the  alloys  of  copper  are  important.  With  gold  it  Alloys 
forms  a fine  yellow  ductile  compound,  used  for  coin  and  ornamental 
work.  With  silver  it  forms  a white  compound,  used  for  plate  and 
coin.!  Lead  and  copper  require  a high  red  heat  for  union  ; the  alloy 

is  gray  and  brittle. 

Of  the  alloys  of  copper  with  the  metals  already  described  the  most 
important  are  brass  and  bell-metal.  It  forms  white  compounds  with 
potassium  and  sodium  ; a reddish  alloy  with  manganese  ; and  a 
gray  one  with  iron. 

1181.  Brass  is  an  alloy  of  copper  and  zinc.  The  metals  are  usu-  Brass, 
ally  united  by  mixing  granulated  copper  with  calamine  (1004)  and 
charcoal : the  mixture  is  exposed  to  heat  sufficient  to  reduce  the 
calamine  and  melt  the  alloy,  which  is  then  cast  into  plates.  The 
relative  proportions  of  the  two  metals  vary  in  the  different  kinds  of 
brass  ; the  best  brass  consists  of  four  parts  copper  to  one  of  zinc. 

This  alloy  is  malleable  and  ductile  when  cold  ; and  its  colour  and 
little  liability  to  rust,  recommend  it  in  preference  to  copper  for  many 
purposes  of  the  arts.l 

1182.  Tutenag  is  said  to  be  an  alloy  of  copper,  zinc,  and  a little  Tutenag, 
iron  ; and  Tombac , Dutch  gold,  Similor,  Prince  Rupert's  metal&nd  pinchbeck, 
Pinchbeck , are  alloys,  containing  more  copper  than  exists  in  brass,  &c* 

and  consequently  made  by  fusing  various  proportions  of  copper  with 
brass.  According  to  Wiegleb,  Manheim  gold  consists  of  three  parts 
of  copper  and  one  of  zinc.  A little  tin  is  sometimes  added,  which, 
though  it  may  improve  the  colour,  impairs  the  malleability  of  the 
alloys 

1183.  Bell-metal  and  bronze  are  alloys  of  copper  and  tin  ; they  Bell-metal 
are  harder  and  more  fusible,  but  less  malleable  than  copper.  The  an  ronze* 
best  bell-metal  is  . composed  of  three  parts  copper  and  one  of  tin  ; the 

Indian  gong,  celebrated  for  the  richness  of  its  tones,  contains  copper 
and  tin  in  this  proportion.  A little  zinc  is  added  to  small  shrill  bells. 

Bronze  consists  of  from  8 to  12  of  tin  with  100  of  copper. 

1184.  Dalton  finds  that  into  all  the  alloys  of  copper  which  are  Alloys 
characterized  by  useful  properties,  the  ingredients  enter  in  atomic  definite 
proportions  ; and  it  is  probable  that  by  attention  to  these  proportions,  comPoun^s“ 
the  manufacture  of  the  artificial  alloys  may  be  greatly  improved. 


* Berzelius,  Ann  de  Chim.  See  also  Vauquelin  on  Sulphurets  of  Copper , lxxx.  265. 

+ See  Gold  and  Silver. 

'+  According  to  Sage,  a very  beautiful  brass  may  be  made  by  mixing  50  grains  of  ox- 
ide of  copper,  100  of  calamine,  400  of  black  flux,  and  30  of  charcoal  powder  3 melt 
these  in  a crucible  till  the  blue  flame  is  no  longer  seen  round  the  cover;  and,  when 
cold,  a button  of  brass  is  found  at  the  bottom,  of  a golden  colour,  and  weighing  one 
sixth  more  than  the  pure  copper  obtained  from  the  above  quantity  of  oxide. 

§ An  alloy,  which,  from  the  resemblance  it  has  in  colour  to  gold,  is  called  Mosaic 
gold , has  been  latelv  prepared  from  equal  parts  of  copper  and  zinc  melted  at  the  lowest 
temperature  at  which  copper  will  fuse. 

Speculum  metal  is  an  alloy  of  copper  and  tin,  with  a little  arsenic ; about  6 copper, 
2 tin,  l arsenic.  On  this  subject  the  reader  is  referred  to  Edwards’s  experiments. 
Nicholson’s  Jour.  4to.  iii. 

38 


298 


Metals — Lead. 


Chap.  IV. 


Ores. 


To  obtain 
pure  lead- 


Properties. 


Action  of 
water, 


Of  acids. 


Protoxide. 


1185.  Vessels  of  copper  used  for  culinary  purposes  are  usually 
coated  with  tin,  to  prevent  the  food  being  contaminated  with  copper. 
Their  interior  surface  is  first  cleaned,  then  rubbed  over  with  sal- 
ammoniac  to  prevent  oxidation  ; the  vessel  is  heated,  a little  pitch 
or  rosin  spread  over  the  surface,  and  a bit  of  tin  rubbed  over  it, 
which  instantly  unites  with  and  covers  the  copper.* 

Lead. 

Symb.  Pb  Equiv.  103.6 

1 186.  Lead  appears  to  have  been  known  in  the  earliest  ages  of  the 
world.  The  natural  compounds  of  this  metal  are  very  numerous. 
The  most  important  is  the  sulphuret,  or  galena , from  which  the  pure 
metal  is  chiefly  procured.  Lead  is  also  found  combined  with  vari- 
ous acids,  with  oxygen,  chlorine,  &c. 

1187.  To  obtain  lead  perfectly  pure,  Berzelius  dissolved  it  in  ni- 
tric acid,  and  crystallized  the  salt  several  times,  till  the  mother  liquor, 
on  adding  carbonate  of  ammonia,  gave  no  traces  of  copper.  The 
pure  nitrate  of  lead,  mixed  with  charcoal,  was  strongly  heated  in  a 
Hessian  crucible;  and  the  lead,  which  separated,  was  kept  for  some 
time  in  fusion,  in  order  to  free  it  entirely  from  charcoal.  The  lead, 
thus  obtained,  when  re-dissolved  in  nitric  acid,  gave  no  trace  of  any 
other  metal. 

1188.  Its  colour  is  bluish-white;  it  is  soft,  flexible,  malleable 
and  ductile.  It  melts  at  about  612°  and  by  slow  cooling  may  be  ob- 
tained in  octohedral  crystals.  Its  sp.  gr.  is  11.352.  At  high  tempe- 
ratures it  absorbs  oxygen,  and  when  in  fusion  a gray  film  is  formed 
on  its  surface,  which  is  a mixture  of  metallic  lead  and  protoxide ; 
by  increasing  the  heat  it  is  dissipated  in  fumes  of  the  protoxide. 

1189.  Lead  undergoes  no  change  in  distilled  water  in  close  ves- 
sels, but  in  open  vessels  is  oxidized  ; the  oxide  combines  also  with 
carbonic  acid  present  in  the  air.  The  presence  of  saline  matter  in 
the  water  retards  the  oxidation,  and  some  salts,  even  in  minute  quan- 
tity, prevent  it  altogether.  Many  kinds  of  spring  water,  owing  to 
the  salts  which  they  contain,  do  not  corrode  lead.t 

1 190.  Lead  is  not  attacked  by  hydrochloric,  or  the  vegetable  acids, 
though  their  presence  often  accelerates  the  absorption  of  oxygen. 
The  only  proper  solvent  for  lead  is  nitric  acid  ; it  oxidizes  it  and 
forms  a salt  of  the  protoxide. 

1191.  Protoxide  of  Lead.  Pb-f-O,  Pb,  or  PbO,  103.6  1 eq.  lead  -f- 
8 1 eq.  oxy.  = 111.6  equiv.,  is  prepared  on  a large  scale  by  collect- 
ing the  gray  film  which  forms  on  the  surface  of  melted  lead,  and 
exposing  it  to  heat  and  air  until  it  acquires  a uniform  yellow  colour. 
In  this  state  it  is  the  massicot  of  commerce  ; and  when  partially  fused 


* The  oxidation  of  copper  plates  is  a matter  of  very  great  importance  in  the  arts, 
and  in  the  case  of  great  and  expensive  works  where  few  impressions  of  an  engraving 
are  taken  and  the  plates  laid  aside  for  a considerable  length  of  time,  a serious  injury 
to  the  plates  is  sustained  by  the  necessity  of  cleaning  them  from  oxide,  when  they  are 
to  be  again  used.  This  may  he  prevented  by  varnishing  the  plates  with  common  lac 
varnish,  which  can  easily  be  removed,  when  requisite,  by  spirits  of  wine.  Brewster’s 
Jour.  i.  76 ; Bost.  Jour.  ii.  206. 

For  method  of  analysis  of  these  alloys,  see  Brande,  xi.  74;  and  for  other  details 
Thomson’s  System— Inorganic  Bodies , i.  601  ; Dumas’  Traits  de  Chim-  iii.  605. 
t Se«  this  subject  discussed  in  Christison’s  Treatise  on  Poisons. 


299 


Red  Oxide  of  Lead. 

the  term  litharge  is  applied  to  it.  As  thus  procured  it  is  al-  Sect-  VL 
ways  mixed  with  red  oxide.  It  may  be  obtained  pure  by  adding 
ammonia  to  a cold  solution  of  nitrate  of  protoxide  of  lead  until  it  is 
faintly  alkaline,  washing  the  precipitated  subnitrate  with  cold  water, 
and,  when  dry,  heating  it  to  redness  for  an  hour  in  a platinum  cru- 
cible. An  open  fire  should  be  used,  and  great  care  taken  to  prevent 
combustible  matter  in  any  form  from  contact  with  the  oxide. 

1192.  Protoxide  of  lead  is  red  while  hot,  but  has  a rich  lemon- proPerlies* 
yellow  colour  when  cold,  is  insoluble  in  water,  fuses  at  a bright  red 

heat,  and  is  fixed  and  unchangeable  in  the  fire.  Its  sp.  gr.  is 
9.4214.  The  fused  protoxide  has  a highly  foliated  texture,  and  is 
very  tough,  so  as  to  be  pulverized  with  difficulty.  By  transmitted 
light  it  is  yellow;  but  by  reflected  light  it  appears  green  in  some 
parts  and  yellow  in  others.  Heated  with  combustible  matters,  the 
protoxide  parts  with  oxygen  and  is  reduced.  It  unites  with  acids, 
and  is  the  base  of  all  the  salts  of  lead,  most  of  which  are  of  a white 
colour. 

1193.  Protoxide  of  lead  is  precipitated  from  its  solutions  by  pure 
alkalies,  as  a white  hydrate,  which  is  redissolved  by  potassa  in  ex- 
cess; as  a white  carbonate,  which  is  the  well  known  pigment  white  Whit«le&d. 
lead , by  alkaline  carbonates  ; as  a white  sulphate  by  soluble  sul- 
phates.; as  a dark  brown  sulphuret  by  hydrosulphuric  acid  ; and  as 
yellow  iodide  of  lead  by  hydriodic  acid  or  iodide  of  potassium.1 * 

The  best  method  of  detecting  the  presence  of  lead  in  wine  or  other  Testof 
suspected  mixed  fluids  is  by  means  of  hydrosulphuric  acid.f  (Fig.  Lead. 
166.) 

1194.  Protoxide  of  lead  unites  readily  with  earthy  substances, 
forming  with  them  a transparent  colourless  glass,  and  is  much  em-  ^nio nofPb 
ployed  for  glazing  earthenware  and  porcelain.  It  enters  in  large  bodies, 
quantity  into  the  composition  of  flint  glass,  $ which  it  renders  more 
fusible,  transparent,  and  uniform. 

1195.  Lead  is  separated  from  its  salts  in  the  metallic  state  by  iron  Separated, 
or  zinc.  The  best  way  of  demonstrating  this  fact  is  by  dissolving  in 

a tall  jar  or  bottle  1 part  of  acetate  of  protoxide  of  lead  in  24  of  water, 
and  suspending  a piece  of  zinc  in  the  solution  by  means  of  a thread. 

The  lead  is  deposited  upon  the  zinc  in  a peculiar  arborescent  form, 
giving  rise  to  the  appearance  called  arbor  Saturni 

1196.  Red  Oxide  of  Lead.  3Pb+40,  or  2Pb0+Pb02,  310.8  3 Red  oxide, 
eq.  lead  — f—  32  4 eq.  oxy.,  or  223.2  2 eq.  prolox.  -(-  119.6  1 eq.  perox.  or  minium. 
s=  342.8  equiv.  This  compound,  the  minium  of  commerce,  is  em- 
ployed as  a pigment,  and  in  the  manufacture  of  flint  glass. 

* With  regard  to  the  poisonous  property  of  the  salts  of  lead,  the  carbonate  is  by  far 
the  most  virulent  poison.  Any  salt  of  lead  which  is  easily  convertible  into  the  carbo-  P«i«onom. 
nate,  as  for  instance  the  subacetate,  is  also  poisonous.  Acetate  of  protoxide  of  lead, 
mixed  with  vinegar  to  prevent  the  formation  of  any  carbonate,  maybe  freely  and  safely 
administered  in  medical  practice.  (Dr  A.  T.  Thomson.) 

t The  sulphuret  of  lead,  after  being  collected  on  a filter  and  washed,  is  to  be  digest- 
ed in  nitric  acid  diluted  with  twice  its  weight  of  water,  until  the  dark  colour  of  the 
sulphuret  disappears.  The  solution  of  the  nitrate  should  then  he  brought  to  perfect 
dryness  on  a watch-glass,  in  order  to  expel  the  excess  of  nitric  acid,  and  the  residue 
be  redissolved  in  a small  quantity  of  cold  water-  On  dropping  a particle  of  iodide  of 
potassium  into  a portion  of  this  liquid,  yellow  iodide  of  lead  will  instantly  appear. 

t Hence  flint  glass  retorts  are  less  suitable  for  some  chemical  processes  than  those  of 
green  glass  without  lead  ; the  latter  are  also  less  fusible.  W. 

SDinoxide  of  Lead.  2Pb-fO,  or  Pb^O,  207.2  2 «q.  lead  8 1 aq.  oxy.  a*  Sig.S 
equiv, 


300 


Metals — Lead . 


Chap.  IV. 


Peroxide. 


Properties. 

Chloride. 


Alloys. 

Solders. 


Eliquation. 


It  is  formed  by  oxidizing  lead  by  heat  and  air  without  allowing  it  to  fuse,  and 
then  exposing  it  in  open  vessels  to  a temperature  of  600°  or  700°,  while  a cur- 
rent of  air  plays  upon  its  surface.  It  slowly  absorbs  oxygen  and  is  converted 
into  minium. 

This  oxide  does  not  unite  with  acids.  When  heated  to  redness 
it  gives  off  pure  oxygen  gas,  and  is  reconverted  into  the  protoxide. 
When  digested  in  nitric  acid  it  is  resolved  into  protoxide  and  perox- 
ide of  lead,  the  former  of  which  unites  with  the  acid,  while  the  latter 
remains  as  an  insoluble  powder.  From  the  facility  with  which  this 
change  is  effected  even  by  acetic  acid,  most  chemists  consider  red  lead 
not  so  much  as  a definite  compound  of  lead  and  oxygen,  but  as  a salt 
composed  of  the  protoxide  and  peroxide.* 

1197.  Peroxide  of  Lead.  Pb-f-20,  Pb,  or  PbO’,  103.6  1 eq.  lead 
+ 16  2 eq.  oxy.  = 119.6  equiv.  This  oxide  may  be  obtained  by 
the  action  of  nitric  acid  on  minium,  as  just  mentioned  ; by  fusing 
protoxide  of  lead  with  chlorate  of  potassa,  at  a temperature  short  of 
redness,  and  removing  the  chloride  of  potassium  by  solution  in  water  ; 
and  by  transmitting  a current  of  chlorine  gas  through  a solution  of 
acetate  of  the  protoxide  of  lead.  The  chloride  formed  is  removed 
by  washing  with  warm  water. 

1 198.  Peroxide  of  lead  is  of  a puce  colour,  is  insoluble  in  water, 
and  is  resolved  by  strong  ox-acids,  such  as  the  sulphuric  and  nitric, 
into  a salt  of  the  protoxide  and  oxygen  gas.  With  hydrochloric  acid 
it  yields  chlorine  gas  and  chloride  of  lead.  At  a red  heat  it  emits 
oxygen  gas  and  is  converted  into  the  protoxide. 

1199.  Chloride  of  Lead.  Pb+Cl,  or  PbCl,  103.6  1 eq.  lead  + 
35.42  1 eq.  chlor.  = 139.02  equiv.  This  compound,  sometimes 
called  horn  lead , is  slowly  formed  by  the  action  of  chlorine  gas  on 
thin  plates  of  lead,  and  may  be  obtained  more  easily  by  adding  hy- 
drochloric acid  or  a solution  of  sea-salt  to  acetate  or  nitrate  of  oxide 
of  lead  dissolved  in  water.  This  chloride  dissolves  to  a considerable 
extent  in  hot  water,  especially  when  acidulated  with  hydrochloric 
acid,  and  separates  on  cooling  in  small  acicular  anhydrous  crystals 
of  a white  colour.  It  fuses  at  a temperature  below  redness,  and 
forms  as  it  cools  a semi-transparent  mass,  which  has  a density  of 
5.133.1 

1200.  Alloys  of  Lead.  The  most  important  are  those  with  tin. 
Common  pewter  consists  of  about  80  parts  of  tin  and  20  of  lead. 
Fine  solder  consists  of  2 parts  of  tin  and  1 of  lead  ; it  fuses  at  about 
360°,  and  is  much  employed  in  tinning  copper.  Coarse  solder  con- 
tains one  fourth  of  tin,  fuses  at  about  500°,  and  is  used  by  plumbers. 
Pot  metal  is  an  alloy  of  lead  and  copper. 

1201.  If  lead  be  heated  so  as  to  boil  and  smoke,  it  soon  dissolves 
pieces  of  copper  thrown  into  it;  the  mixture,  when  cold,  is  brittle. 
The  union  of  the  two  metals  is  remarkably  slight ; for,  upon  expos- 
ing the  mass  to  a heat  no  greater  than  that  in  which  lead  melts,  the 
lead  almost  entirely  runs  off  by  itself.  This  process  is  called  eliqua- 
tion. The  coarser  sorts  of  lead,  which  owe  their  brittleness  and  gra- 


* This  was  long  considered  as  a sesquioxide,  an  error  corrected  by  Dalton,  I\ew 
System,  of  Che vi.  ii.  41.  T. 

t For  other  compounds  see  Turner’s  Elements,  376. 


Mercury. 

inflated  texture  to  an  admixture  of  copper,  throw  it  up  to  the  sur-  Sect,  vn. 
face  on  being-  melted  by  a moderate  heat.* 


Section  VII. — Metals , the  oxides  of  which  are  reduced  to  the  metal - 
lie  state  by  a red  heat . 

1202.  Mercury  or  Quicksilver , Hg.  202  eq.,t  is  the  only  one  of  Mercury, 
the  metals  that  retains  a fluid  form  at  the  ordinary  temperature  of 

the  atmosphere* 

The  principal  ore  of  this  metal  is  the  sulphuret,  or  native  cinna-  Ore. 
bar , from  which  the  mercury  is  separated  by  distillation  with  quick- 
lime or  iron  filings. 

1203.  Mercury  is  a brilliant  white  metal,  having  much  of  the  Boiling 
colour  of  silver,  whence  the  terms  hydrargyrum , argentum  vivum,  Pomt- 
and  quicksilver.  It  has  been  known  from  very  remote  ages.  Ac- 
cording to  Crichton  it  boils  and  becomes  vapour  at  656°  F.,  680° 
according  to  Petit  and  Dulong,  670°  Brande,  and  662°  T. 

It  also  rises  in  vapour  in  small  portions  at  the  common,  tempera- 
ture of  the  atmosphere,  particularly  in  a vacuum. 

1204.  When  the  temperature  of  mercury  is  considerably  increas-  Vapour 
ed  above  its  boiling  point,  the  vapour  acquires  great  expansive  force, 

and  the  power  of  bursting  the  strongest  vessels.  Gay-Lussac  has 
calculated  that  the  vapour  of  mercury  is  12.01  more  dense  than 
oxygen  gas,  and  that  the  liquid  metal  in  becoming  gaseous,  increase* 
in  volume  961  times. 

1205.  When  the  temperature  of  mercury  is  reduced  to  about  Freezing. 
— 39°  or  40°  F.,  it  becomes  solid  and  malleable. 

By  congelation  it  acquires  an  increase  of  sp.  gr. ; and,  therefore, 
unlike  other  metals,  the  congealed  portion  sinks  to  the  bottom  of  a 
fluid  mass  of  mercury.  Its  sp.  gr.  at  47°  above  0 F.  being  13.568, 
it  is  increased  by  congelation,  to  15.612. 

Mercury,  if  quite  pure,  is  not  tarnished  in  the  cold  by  exposure  to 
air  and  moisture ; but  if  it  contain  other  metals,  the  amalgam  of 
those  metals  oxidizes  readily,  and  collects  a film  upon  its  surface. 

1206.  Mercury  is  sometimes  adulterated  with  the  alloy  of  lead  Adultera* 
and  bismuth,  a fraud  easily  detected  by  the  want  of  its  due  fluidity,  Jete’aetT 
and  by  its  not  being  perfectly  volatile,  but  leaving  a residuum  when 
boiled  in  a platinum  or  iron  spoon. t 


* Lead  combines  with  Iodine,  Fluorine,  &c.,  for  which  see  Turner,  Brande, 
Thomson  and  others.  + Turner,  Phil.  Trans.,  1833,  part  ii. 

t Mercury  which  is  chemically  impure  will  soon  acquire  adhesive  films  on  its  sur- 
face, even  when  cleansed  of  mechanical  impurities,  and  with  a rapidity  dependent 
on  the  agitation  of  the  metal  or  extension  of  surface.  These  interfere  chemically 
when  the  metal  is  to  be  used  in  forming  combinations,  and  mechanically  in  its  uses 
in  the  trough  in  electro-magnetic  experiments,  and  in  the  construction  of  barometers 
and  thermometers. 

The  purification  of  mercury  from  metals  by  distillation  should  be  performed  in  an 
iron  retort,  a portion  of  clean  iron  and  copper  filings  having  been  introduced  with  the  purified. 
mercury,  which  should  be  condensed  and  received  in  clean  water.  This  process, 
however,  is  not  wholly  unobjectionable,  as  both  zinc  and  arsenic  will  pass  over,  and 
these  metals  are  often  present.  A very  useful  method  is  to  put  from  naif  an  inch  to 
an  inch  in  depth  of  mercury,  mto  a large  earthenware  pan,  and  to  pour  over  it  sulph- 
uric acid  diluted  with  twice  its  weight  of  water.  The  substances  should  be  left  to- 
gether for  a week  or  two,  being  frequently  agitated.  The  metal  and  acid  ara  then  to 


302 

Chap  IV. 

Action  of 
acids. 

Protoxide. 


Properties. 


Peroxide, 
or  red  pre- 
cipitate. 


Process. 


Properties. 


Metals — Mercury « 

1207.  The  only  acids  that  act  on  mercury  are  the  sulphuric  and 
nitric,  the  former  requires  the  aid  of  heat  and  sulphurous  acid  is 
disengaged  (530) ; the  latter  acts  at  all  temperatures  and  binoxide  of 
nitrogen  is  evolved  (455). 

1208.  Protoxide  of  Mercury , Hg-(-0,  Hg,  or  HgO,  202  1 eq. 
mere.  8 1 eq.  oxy.  = 210  equiv.  This  oxide  which  is  a black 
powder,  insoluble  in  water,  is  best  prepared  by  the  process  recom- 
mended by  Donovan.*  This  consists  in  mixing  calomel  briskly  in  a 
mortar  with  pure  potassa  in  excess,  so  as  to  effect  its  decomposition 
as  rapidly  as  possible  : the  protoxide  is  then  washed  with  cold  water, 
and  dried  spontaneously  in  a dark  place.  These  precautions  are 
rendered  necessary  by  the  tendency  of  the  protoxide  to  resolve  it- 
self into  the  peroxide  and  metallic  mercury,  a change  which  is 
easily  effected  by  heat,  by  the  direct  solar  rays,  and  even  by  day- 
light. It  is  on  this  account  very  difficult  to  procure  protoxide  of 
mercury  in  a state  of  absolute  purity. 

1209.  It  is  a black  powder,  insoluble  in  water,  uniting  with  acids, 
but  a weak  alkaline  base.  The  alkalies  precipitate  it  from  solutions 
of  its  salts  as  the  black  protoxide. 

It  is  thrown  down  as  a white  carbonate  by  alkaline  carbonates,  but 
soon  becomes  dark  from  loss  of  its  carbonic  acid  ; as  calomel  by 
hydrochloric  acid  or  any  soluble  chloride,  and  as  black  prolosulphur- 
et  by  hydrosulphuric  acid  ; this  last  is  the  best  test  of  its  pres- 
ence. 

1210.  Peroxide  of  Mercury , Hg+20,  Hg,  or  HgO2,  202  1 eq. 
mere.  -\-  16  2 eq.  oxy.  = 218  equiv.  This  oxide  may  be  formed 
either  by  the  combined  agency  of  heat  and  air,  or  by  dissolving 
mercury  in  nitric  acid,  and  exposing  the  nitrate  so  formed  to  a 
temperature  just  sufficient  for  expelling  the  whole  of  the  nitric 
acid.t  It  is  commonly  known  by  the  name  of  red  precipitate. X 

1211.  When  prepared  by  heat  the  process  may  be  conducted  by  intro- 
ducing into  a flat-bottom  matrass,  (Fig.  182,)  about  4 ounces  of  mercury,  and 
placing  it  in  a sand-bath,  heated  to  the  boiling  point  of  the  metal.  In  about 
a month's  time  nearly  the  whole  is  converted  into  oxide.  Air  is  freely 
admitted  by  the  tube,  while  its  length  prevents  the  escape  of  mercurial 
vapour,  which  condenses  and  falls  back  into  the  body  of  the  vessel;  the 
remaining  portion  of  running  mercury  may  be  driven  off  by  exposing  it 
in  a basin  to  a heat  just  below  redness. 

1212.  Peroxide  of  mercury,  thus  prepared,  is  commonly  in  the 
form  of  shining  crystalline  scales  of  a nearly  black  colour  while  hot, 


be  separated,  the  latter  preserved  for  a similar  operation  in  future,  and  the  former 
washed,  dried  and  cleansed  mechanically,  by  squeezing  through  sbamois  leather,  by 
agitation  with  damp  loaf  sugar,  passing  through  a paper  funnel,  &c. — See  Faraday’s 
Chem.  Manip.  sect.  xx. 

* Ann.  of  Phil.  xiv. 

+ The  peroxide  prepared  from  the  nitrate  almost  always  contains  a trace  of  nitric 
acid,  which  may  he  detected  by  heating  it  in  a clean  glass  tube  by  means  of  a spirit- 
lamp  ; a yellow  ring,  formed  of  subnitrate  of  peroxide  of  mercury,  collects  within  the 
tube  just  above  the  part  which  is  heated.  (Clarke.) 

t H'jdrargyri  oxidum  rubrum  of  the  Pharmacop.  In  the  manufacture  of  this  com- 
pound at  Apothecaries’  Hall  (Loud.)  100  lhs.  of  mercury  are  boiled  with  48  lbs.  of 
nitric  acid  (sp.  gr.  1.43)  and  by  proper  evaporation  and  application  of  a dull  red  heat, 
112  ibs.  of  the  hydrarpryri  niirico  oxidum  are  obtained.  B 


303 


Protochloride  of  Mercury. 

but  red  when  cold:  when  very  finely  levigated,  the  peroxide  has  Sect,  vii. 
in  orange  colour.  It  is  soluble  to  a small  extent  in  water,  forming 
i solution  which  has  an  acrid  metallic  taste,  and  is  poisonous. 

When  heated  to  redness,  it  is  converted  into  metallic  mercury  and 
ixygen.  Long  exposure  to  light  has  a similar  effect.* 

1213.  Some  of  the  neutral  salts  of  this  oxide,  such  as  the  nitrate  Action of 
md  sulphate,  are  converted  by  water,  especially  at  a boiling  tern-  wa  er>  c' 
jerature,  into  insoluble  yellow  subsalts,  leaving  a strongly  acid  so- 

ution,  in  which  a little  of  the  original  salt  is  dissolved.  The  oxide 
:s  separated  from  all  acids  as  a red,  or  when  hydratic  as  a yellow 
precipitate,  by  the  pure  and  carbonated  fixed  alkalies.  Ammonia 
ind  its  carbonate  cause  a white  precipitate,  which  is  a double  salt, 
consisting  of  one  equivalent  of  the  acid,  one  equivalent  of  the  pe- 
roxide, and  one  equivalent  of  ammonia.  The  oxide  is  readily  re- 
iuced  to  the  metallic  state  by  metallic  copper. 

1214.  Protochloride  of  Mercury , Hg-[-Cl,  or  HgCl,  202  1 eq.  Protochlo- 
merc.  -(-  35.42  1 eq.  chlor.  = 237.42  equiv.  This  compound,  com- ^’jor  cal" 
rnonly  termed  calomel , is  first  mentioned  by  Crollius,  early  in  the 
seventeenth  century.! 

1215.  It  is  always  generated  when  chlorine  comes  in  contact  with  Obtained, 
mercury  at  common  temperatures  ; and  also  by  the  contact  of  me- 

;allic  mercury  and  the  bichloride.  It  may  be  made  by  precipitation, 
by  mixing  nitrate  of  protoxide  of  mercury  in  solution  with  hydro- 
chloric acid  or  any  soluble  chloride.  It  is  more  commonly  prepared 
by  sublimation.  This  is  conveniently  done  by  mixing  272.84  parts 
cr  one  equivalent  of  the  bichloride  with  202  parts  or  one  equiva- 
lent of  mercury,  until  the  metallic  globules  entirely  disappear,  and 
then  subliming.  When  first  prepared  it  is  always  mixed  with 
some  corrosive  sublimate,  and,  therefore,  should  be  reduced  to 
powder  and  well  washed,  before  being  employed  for  chemical  or 
medical  purposes.! 

1216.  When  obtained  by  sublimation  it  is  in  semi-transparent  Properties, 
crystalline  cakes ; but  as  formed  by  precipitation,  it  is  a white  pow- 
der. Its  density  is  7.2.  At  a heat  short  of  redness,  but  higher 

than  the  subliming  point  of  the  bichloride,  it  rises  in  vapour  with- 
out previous  fusion  ; but  during  the  sublimation  a portion  is  always 


* Guibourt. 

t The  first  directions  for  its  preparation  are  given  by  Beguin,  in  the  Tyrocinium 
Chemicum,  published  in  1608.  He  calls  it  draco  mitigatus.  Several  other  fanciful 
names  have  been  applied  to  it,  such  as  aquila  mitigata , manna  metallorum,  panchy- 
magogum  minerale,  sublimatum  dulce,  mercurius  didcis,  fyc. 

$ It  was  formerly  the  custom  to  submit  calomel  to  very  numerous  sublimations, 
under  the  idea  of  rendering  it  mild;  but  these  often  tended  to  the  production  of  cor-  cusora- 
rosive  sublimate;  and  the  calomel  of  the  first  sublimation,  especially  if  a little  ex- 
cess of  mercury  be  found  in  it,  is  often  more  pure  than  that  afforded  by  subsequent 
operations.  The  following  are  the  directions  given  in  the  hand.  Pharmacop. 

“ Take  of  oxymuriate  of  mercury,  1 lb. 

purified  mercury,  by  weight , 9 oz. 

Rub  them  together  until  the  metallic  globules  disappear  ; then  sublime  : take  out  the 
sublimed  mass,  reduce  it  to  powder,  and  sublime  it  in  the  same  manner  twice  more 
successively;  bring  it  to  the  state  of  a very  fine  powder;  throw  this  into  a 
large  vessel,  full  of  water;  then  stir  it,  and,  after  a short  interval,  pour  the  superna- 
tant turbid  solution  into  another  vessel,  and  set  it  by,  that  the  powder  may  subside. 

Lastly,  having  poured  away  the  water,  dry  the  powder.” 

; It  will  be  observed  that  in  these  processes  the  operation  consists  in  reducing  the 
bichloride  to  the  state  of  protochloride  by  the  addition  of  mercury. 


304 

Chap.  IV. 


Bichloride, 
or  corrosive 
sublimate. 


Theory. 


Characters. 


Action  of 
light, 

Of  alkalies, 

Proceu. 


Metals — Mercury . 


resolved  into  mercury  and  the  bichloride.  It  is  yellow  while  warm, 
but  recovers  its  whiteness  on  cooling.  It  is  distinguished  from  the 
bichloride  by  not  being  poisonous,  by  having  no  taste,  and  by  being 
exceedingly  insoluble  in  water.  Acids  have  little  effect  upon  it ; 
but  pure  alkalies  decompose  it,  separating  the  black  protoxide  of 
mercury. 

1217.  Bichloride  of  Mercury,  Hg-}-2Cl,  or  HgCP,  202  1 eq.  mere, 
-f-  70.84  2 eq.  chlor.  = 272.84  equiv.  When  mercury  is  heated 
in  chlorine  gas,  it  takes  fire,  and  burns  with  a pale  red  flame,  form- 
ing the  well  known  medicinal  preparation  and  virulent  poison 
corrosive  sublimate , or  bichloride  of  mercury.  It  is  prepared  for 
medical  purposes  by  subliming  a mixture  of  bisulphate  of  the  per- 
oxide of  mercury  with  chloride  of  sodium  or  sea-salt.*  The  ex- 
act quantities  required  for  mutual  decomposition  are  298.2  parts  or 
one  equivalent  of  the  bisulphate,  to  117.44  parts  or  two  equivalents 
of  the  chloride.  Thus, 

1 eq.  Bisulphate  of  Mercury.  | 2 eq.  Chloride  of  Sodium. 

Sulphuric  Acid  80.2  or  2 eq.  2P>03  | Chlorine  . 7(1.84  or  2 eq.  2C1. 

Perox.  of  Merc.  . 218  or  1 eq.  HgO-’  | Sodium  46.6  or  2 eq.  2Na 

298.2  HgO*q-2S03  | 117.44  2 (Na+Cl) 


and  by  mutual  interchange  of  elements  they  produce 


1 eq.  Bichloride  of  Mercury. 
Mercury  . . 202  or  1 eq.  Hg. 

Chlorine  . - 70.84  or  2 eq.  2C1 

272.84  Hg-f2Cl 


2 eq  Sulphate  of  Soda 
Soda  62.6  or  2 eq.  2NaO 

Sulph.  Acid  . 80.2  or  2 eq.  2S03 

142.8  2 (NaO-fSO3) 


The  products  have  exactly  the  same  weight  (272.84  -j-  142.8  = 
415.64)  as  the  compounds  (298.2  -|-  117.44  = 415.64)  from  which 
they  were  prepared. 

1218.  Bichloride  of  mercury  is  usually  seen  in  the  form  of  a per- 
fectly white  semi-transparent  mass,  exhibiting  the  appearance  of  im- 
perfect crystallization.  It  is  sometimes  procured  in  quadrangular 
prisms.  Its  sp.  gr.  is  5.2,  its  taste  is  acrid  and  nauseous,  leaving 
a peculiar  metallic  and  astringent  flavour  upon  the  tongue.  It  dis- 
solves in  20  parts  of  water  at  60°,  and  but  twice  its  weight  at  212°. 
It  is  more  soluble  in  alcohol  than  in  water.  When  heated,  it  readi- 
ly sublimes  in  the  form  of  a dense  white  vapour,  strongly  affecting 
the  nose  and  mouth.  It  dissolves  without  decomposition  in  hydro- 
chloric, nitric,  and  sulphuric  acids  : the  alkalies  and  several  of  the 
metals  decompose  it. 

1219.  Its  aqueous  solution  is  gradually  decomposed  by  light,  cal- 
omel being  deposited. 

The  pure  and  carbonated  fixed  alkalies  throw  down  the  peroxide 
of  mercury  from  a solution  of  corrosive  sublimate ; ammonia  on  the 


* The  following  is  the  process  followed  at  Apothecaries  Hall,  (Lnnd.^  50  lbs.  of 
mercury  are  boiled  with  70  lbs.  of  sulphuric  add,  to  dryness,  in  a cast-iron  vessel  j 
62  lbs.  of  the  dry  salt  are  triturated  with  40  1-2  lbs.  of  mercury,  until  the  globules 
disappear,  and  34  lbs  of  common  salt  are  then  added.  This  mixture  is  submitted  to 
heat  in  earthen  vessels,  and  from  95  to  100  lbs.  of  calomel  are  the  result.  It  is  to  be 
washed  in  large  quantities  of  distilled  water,  after  having  been  ground  to  a fine  and 
inapelpable  powder. 


305 


Iodides  of  Mercury. 

contrary,  causes  the  deposition  of  a white  matter  which  is  common-  Sect,  vn. 
Jy  known  as  white  precipitate  * White  pre- 

1220.  The  presence  of  mercury  in  a fluid,  supposed  to  contain  cipitate. 
corrosive  sublimate,  may  be  detected  by  concentrating  and  digesting  D.e^tion 
it  with  an  excess  of  pure  potassa.  Peroxide  of  mercury,  which0  merculTi 
subsides,  is  then  sublimed  in  a small  glass  tube  by  means  of  a spirit- 

lamp,  and  obtained  in  the  form  of  metallic  globules.  When  the 
bichloride  is  mixed  with  organic  substances,  Christison  recommends 
that  the  liquid,  without  previous  filtration,  be  agitated  with  a fourth 
of  its  volume  of  ether,  which  separates  the  poison  from  the  aqueous 
part  and  rises  to  the  surface.  The  ethereal  solution  is  then  evapora- 
ted on  a watch-glass,  the  residue  dissolved  in  water,  and  the  mercu- 
ry precipitated  in  the  metallic  state  by  protochloride  of  tin  at  a 
boiling  temperature.! 

1221.  Avery  elegant  method  of  detecting  the  presence  of  mer-  Sylvester’s 
cury  is  to  place  a drop  of  the  suspected  liquid  on  polished  gold,  and  method, 
to  touch  the  moistened  surface  with  a piece  of  iron  wire  or  the  point 

of  a penknife,  when  the  part  touched  instantly  becomes  while,  owing 
to  the  formation  of  an  amalgam  of  gold.  This  process  was  orig- 
inally suggested  by  Sylvester,  and  has  since  been  simplified  by 
Paris.! 

1222.  Many  animal  and  vegetable  solutions  convert  bichloride  of  Action  of 
mercury  into  calomel.  Some  substances  effect  this  change  slowly  ; a umen' 
while  others,  and  especially  albumen,  produce  it  in  an  instant. 

Into  a solution  of  corrosive  sublimate  drop  a solution  of  albumen,  made  by  Exp. 
mixing  a portion  of  white  of  egg  with  water,  a white  flocculent  precipitate 
subsides,  which  Orfila  has  shown  to  be  a compound  of  calomel  and  albumen, 
and  which  he  has  proved  experimentally  to  be  inert.*  Consequently,  a solu- 
tion of  the  white  of  eggs  is  an  an  antidote  to  poisoning  by  corrosive  sublimate. 

1223.  Protiodide  of  Mercury , Hg-f-I,  or  Hgl,  202  1 eq.  mere,  -f-  Protiodide. 
126.3  1 eq.  iod.  ±=  328.3  equiv.,  is  obtained  by  mixing  nitrate  of 
protoxide  of  mercury  in  solution,  with  iodide  of  potassium  ; when 

the  latter  is  added  to  the  mixed  nitrates  of  the  protoxide  and  perox- 
ide of  mercury,  the  latter  in  excess,  the  sesquiodide  falls. 

1224.  Biniodide  of  Mercury^  Hg-j-21,  or  Hgl2,  202  1 eq.  mere.  Biniodide. 
-j-252.6  2 eq.  iod.  = 454.6  equiv.  This  compound  is  formed  by 
mixing  nitrate  of  the  peroxide  or  bichloride  of  mercury  with  iodide 

of  potassium  in  solution,  and  falls  as  a rich  red-coloured  powder  of 
a tint  which  vies  in  beauty  with  that  of  vermilion,  though  unfortu- 


* This  substance  has  been  recently  examined.*  It  was  found  that  a slight  excess 
of  ammonia  being  added,  just  one  half  the  chlorine  of  the  corrosive  sublimate  was 
separated,  the  other  half  remaining  in  the  solution  with  the  ammonia.  The  precipitate, 
nevertheless,  did  not  contain  calomel.  It  was  found  to  be  composed  of 
Mercury  . . 78.6  Ammonia  . . 6.77 

Chlorine  . . 13.S5  Hygrometric  water  > 73 

loss  and  oxygen,  $ 

Its  atomic  constitution  would  appear  from  this  analysis  to  contain  the  compound 
radical  which  is  the  base  of  the  amides, 

+ If.  as  is  probable,  most  of  the  poison  is  already  converted  into  calomel,  and 
thereby  rendered  insoluble,  as  many  vegetable  fibres  should  be  picked  out  as  possible, 
and  the  whole  at  once  digested  with  protcchloride  of  tin.  The  organic  substances 
are  then  dissolved  in  a hot  solution  of  caustic  potassa,  and  the  insoluble  parts  washed 
and  sublimed  to  separate  the  mercury, t 
t Medical  Jurisprudence,  by  Paris  and  Fonblanque.  § Toxicologie , vol,  i, 

* Kane  in  I vans.  Irish  ,$sad.  xvii,  f Christison  on  Poisons . 

39' 


306 


Chap.  IV. 


Effect  of 
heat. 


Sulphurets. 


Bisulphu- 
ret, or  cin- 
nabar. 


Procei*. 


Metals — Mercury . 

nately,  the  colour  is  less  permanent.  Though  insoluble  in  water,  it 
dissolves  freely  in  an  excess  of  either  of  its  precipitants.  If  taken 
up  in  a hot  solution  of  nitrate  of  peroxide  of  mercury,  the  biniodide 
crystallizes  out  on  cooling  in  scales  of  a beautiful  red  tint.  The 
same  crystals  separate  from  a solution  in  iodide  of  potassium;  but 
if  the  liquid  be  concentrated,  a double  iodide  of  mercury  and  po- 
tassium subsides. 

1225.  The  biniodide,  when  exposed  to  a moderate  heat,  gradually 
becomes  yellow ; and  the  particles,  though  previously  in  powder, 
acquire  a crystalline  appearance.  At  about  400°  it  forms  a yellow 
liquid  which  slowly  sublimes  in  small  transparent  scales,  or  in  large 
rhombic  tables,  when  a considerable  quantity  is  sublimed.  The 
crystals  retain  their  yellow  colour  at  60°  if  kept  very  tranquil ; but 
if  the  temperature  be  below  a certain  point,  or  they  are  rubbed  or 
touched,  they  quickly  become  red.*  This  phenomenon  is  entirely 
due  to  a change  in  molecular  arrangement:  the  different  colours  so 
often  witnessed  in  the  same  substances  at  different  temperatures,  as 
in  peroxide  of  mercury  and  the  protoxides  of  lead  and  zinc,  appear 
to  be  phenomena  of  the  same  nature.! 

1226.  Protosulphuret  of  Mercury , Hg-f-S,  or  HgS,  202  1 eq. 
mere.  + 16.1  1 eq.  sulph.  = 218.1  equiv.,  may  be  prepared  by 
transmitting  a current  of  hydrosulphuric  acid  gas  through  a dilute 
solution  of  nitrate  of  protoxide  of  mercury,  or  through  water  in 
which  calomel  is  suspended.  It  is  a black-coloured  substance,  which 
is  oxidized  by  digestion  in  strong  nitric  acid.  When  exposed  to 
heat  it  is  resolved  into  the  bisulphuret  and  metallic  mercury. 

1227.  Bisulphuret  of  Mercury , Hg-|-2S,  or  HgS2,  202  1 eq. 
mere.  + 32.2  2 eq.  sulph.  = 234.2  equiv.,  is  formed  by  fusing 
sulphur  with  about  six  times  its  weight  of  mercury,  and  subliming 
in  close  vessels.  When  procured  by  this  process  it  has  a red  colour, 
and  is  known  by  the  name  of  factitious  cinnabar X Its  tint  is  great- 
ly improved  by  being  reduced  to  powder,  in  which  state  it  forms  the 
beautiful  pigment  vermilion.  It  may  be  obtained  in  the  moist 
way  by  pouring  a solution  of  corrosive  sublimate  into  an  excess  of 
hydrosulphate  of  ammonia.  A black  precipitate  subsides,  which 
acquires  the  usual  red  colour  of  cinnabar  when  sublimed. 

1228.  Cinnabar  is  not  altered  by  exposure  to  air  or  moisture; 
when  heated  to  dull  redness  in  an  open  vessel,  the  sulphur  forms 
sulphurous  acid,  and  the  mercury  escapes  in  vapour.  It  is  decom- 
posed by  distillation  with  fixed  alkalies,  lime,  and  baryta,  and  by 


* This  appears  to  have  begn  first  noticed  by  Hayes,  who  has  given  an  economical 
process  for  preparing  the  compound  in  Amer.  Jour.  xvi.  174. 

+ Sesquiodide  of  Mercury,  2Hg+3l,  or  Hg2I3,  404  2 eq.  mere.  -+-  378.9  3 eq.  iod. 
= 782.9  equiv. 

Protobromide  of  Mercury,  Hg-fBr,  or  HgBr,  202  1 eq.  mere,  -f-  78.4  1 eq.  brom. 
= 280.4  equiv. 

Bibromide  of  Mercury,  Hg+2Br.  or  HgBr2,  202  1 eq.  mere,  -f  156.8  2 eq.  brom. 
=358.8  equiv. 

t In  the  manufacture  of  cinnabar  8 parts  of  mercury  are  mixed  in  an  iron  pot  with 
one  of  sulphur,  and  made  to  combine  by  a moderate  heat,  and  constant  stirring  ■,  this 
compound  is  then  transferred  to  a glass  subliming  vessel,  (on  a small  scale  a Flor- 
ence flask  answers  perfectly,)  and  heated  to  redness  in  a sand-bath  ; a quantity  of 
mercury  and  of  sulphur  evaporate,  and  a sublimate  forms  which  is  removed,  and  rub- 
bed or  levigated  into  a very  fine  powder. 


Silver . 307 

several  of  the  metals.  When  adulterated  with  red  lead  it  is  not  en-  Sect,  vn. 
tirely  volatile. 

1229.  Native  Cinnabar  is  the  principal  ore  of  mercury;  it  occurs  Native  cin- 
massive  and  crystallized  of  various  colours,  sometimes  appearing  nabar’ 
steel-gray,  at  others  bright  red.  Native  mercury  and  native  amal- 
gam of  silver  sometimes  accompany  it. 

1230.  When  equal  parts  of  sulphur  and  mercury  are  triturated 
together  until  metallic  globules  cease  to  be  visible,  the  dark  coloured  Ethiops. 
mass  called  ethiops  mineral  results,  which  Brande  has  proved  to  be  a 
mixture  of  sulphur  and  bisulphuret  of  mercury.^ 

1231.  Mercury  combines  with  most  of  the  other  metals,  and  forms  Amalgams, 
a class  of  compounds  which  have  been  called  amalgams.  These  are 
generally  brittle  or  soft.  One  part  of  potassium  with  70  of  mercury 
produces  a hard  brittle  compound.  If  mercury  be  added  to  the  liquid 

alloy  of  potassium  and  sodium,  an  instant  solidification  ensues,  and 
heat  enough  to  inflame  the  latter  metal  is  evolved.  The  amalgams 
of  gold  and  silver  are  employed  in  gilding  and  silvering. 

An  amalgam  of  2 parts  of  mercury,  1 of  bismuth,  and  1 of  lead,  is 
fluid,  and  when  kept  for  some  time,  deposits  cubic  crystals  of  bis- 
muth.! 

1232.  By  combination  with  mercury,  metals  that  are  not  easily  Oxidation 
oxidized,  acquire  a facility  of  entering  into  union  with  oxygen, 

Thus  gold  and  silver,  when  combined  with  mercury,  are  oxidized  by  bymercury, 
ignition  in  contact  with  air.  This  fact  furnishes  a striking  illustra- 
tion of  the  effect  of  overcoming  the  aggregative  affinity  of  bodies  in 
promoting  chemical  union. 

1233.  When  mercury  is  negatively  electrized  in  a solution  of  am- 
monia, or  when  an  amalgam  of  potassium  and  mercury  is  placed 
upon  moistened  hydrochlorate  of  ammonia,  the  metal  increases  in 
volume,  and  becomes  of  the  consistency  of  butter,  an  appearance 
which  has  sometimes  been  called  the  metallization  of  ammonia.  It 
has  suggested  some  hypotheses  concerning  the  nature  of  ammonia 
and  the  metals  (731). t 

Silver. 

Symb.  Ag  Equiv.  108 

1234.  Silver  is  found  native , and  in  a variety  of  combinations  ; it  Silver, 
was  known  to  the  ancients.  Native  silver  occurs  crystallized  in  oc- 
tahedral or  cubic  crystals,  arborescent  and  capillary.  It  is  seldom 
pure,  but  contains  small  portions  of  other  metals,  which  affect  its 
colour  and  ductility.  It  is  chiefly  found  in  primitive  countries.  In 
Peru  and  Mexico  are  the  richest  known  mines  of  native  silver. 

1235.  Pure  silver  may  be  obtained  from  goldsmiths’,  or  standard  Pure,  pro- 
silver, by  dissolving  it  in  nitric  acid  and  precipitating  by  means  of  a cess  for- 


* Jour,  of  Sci.  vol.  xviii.  p.  294. 

loduretted  Bichloride  of  Mercury.  20HgCl2+I,  6456.8  20  eq.  bichlor.  + 126.3  1 
eq.  iodine  = 5583.1  equiv. 

Iodobichloride  of  Mercury.  40HgC12-|-HgI2,  10913.6  40  eq.  bichlor.  + 454.6  1 eq. 
biniodide  = 11368.2  equiv. 

t For  the  method  of  making  an  amalgam  of  copper  see  Aikin’s  Did.,  art.  Mercury , 
p.  92;  Thomson’s  Chem.  oflnorg.  Bodies,  i.  626. 

t Upon  this  subject  the  student  may  consult  Gay-Lussac  and  Thenard  ( Recherche s 
Phys.  Chim.  vol.  i.);  and  Berzelius  (Lehrbuch  1). 


308 


Metals — Silver. 


_Ohap.iv.  clean  piece  of  copper,  washing  with  pure  water,  and  then  digesting 
in  ammonia,  to  remove  the  copper. 

Another.  1236.  A better  process  is  to  decompose  chloride  of  silver  by  means 
of  carbonate  of  potassa. 

For  this  purpose  precipitate  a solution  of  nitrate  of  oxide  of  silver  with  chloride 
of  sodium,  wash  the  precipitate  with  water,  and  dry  it.  Then  put  twice  its 
weight  of  carbonate  of  potassa  into  a clean  Hessian  or  black  lead  crucible,  heat  it 
to  redness,  and  throw  the  chloride  by  successive  portions  into  the  fused  alkali. 
Effervescence  takes  place  from  the  evolution  of  carbonic  acid  and  oxygen  gases, 
chloride  of  potassium  is  generated,  and  metallic  silver  subsides  to  the  bottom. 
The  pure  metal  may  be  granulated  by  pouring  it  while  fused  from  a height  of 
seven  or  eight  feet  into  a vessel  of  water.* 

Characters.  1237.  Silver  has  a pure  white  colour,  and  considerable  brilliancy. 

Its  sp.  gr.  is  10.51  (hammered).  It  is  so  malleable  and  ductile,  that  it 
may  be  extended  into  leaves  not  exceeding  a ten  thousandth  of  an 
inch  in  thickness,  and  drawn  into  wire  finer  than  a human  hair. 

Properties.  1238.  It  melts  at  a bright  red  heat,  1873°  F.,  and  when  in  fusion 
appears  extremely  brilliant.  It  resists  the  action  of  air  and  moisture, 
and  does  not  oxidize  ;t  the  tarnish  of  silver  is  occasioned  by  sulphu- 
rous vapours  ; it  takes  place  very  slowly  upon  the  pure  metal,  but 
more  rapidly  upon  the  alloy  with  copper  used  for  plate,  and  was 
found  by  Proust  to  consist  of  sulphuret  of  silver. 

Effect  of  1239.  Pure  water  has  no  effect  upon  the  metal;  but  if  the  water 

water,  &c.  contajn  vegetable  or  animal  matter,  it  often  slightly  blackens  its  sur- 
face in  consequence  of  the  presence  of  sulphur.  If  an  electric  explo- 
sion be  passed  through  fine  silver  wire,  it  burns  into  a black  powder, 
which  is  an  oxide  of  silver.  In  the  Voltaic  circle  it  burns  with  a 
fine  green  light,  and  throws  off  abundant  fumes  of  oxide.  Exposed 
to  an  intense  white  heat,  it  boils  and  evaporates.  If  suddenly  cooled, 
it  crystallizes  during  congelation,  often  shooting  out  like  a cauli- 
flower, and  throwing  small  particles  of  the  metal  out  of  the  crucible. 

Cupella-  1240.  Silver  is  not  unfrequently  obtained  in  considerable  quanti- 
ties from  argentiferous  sulphuret  of  lead,  which  is  reduced  in  the 
usual  way  and  then  cupelled  ; the  oxide  of  lead  thus  procured  is  af- 
terwards reduced  by  charcoal. t 

* Thomson  found  it  difficult  to  obtain  silver  free  from  copper,  even  when  reduced 
from  the  chloride,  hut  accomplished  the  object  by  first  washing  the  chloride  with  di- 
luted nitric  acid,  which  removed  the  copper.  First  Principles,  ii.  436. 

t When  fused  in  open  vessels  it  absorbs  oxygen  amounting  sometimes  to  twentytwo 
times  its  volume,  but  parts  with  it  in  the  act  of  becoming  solid.  T. 

t The  principle  of  its  separation  from  lead  is  founded  on  the  different  oxidability  of 
lead  and  silver,  and  on  ihe  ready  fusibility  oflitharge.  The  lead  obtained  from  those 
kinds  of  galena  which  are  rich  in  sulphuret  of  silver  is  kept  at  a red  heat  in  a flat  fur- 
nace, with  a draught  of  air  constantly  playing  on  its  surface;  the  lead  is  thus  rapidly 
oxidized;  and  as  the  oxide,  at  the  moment  of  its  formation,  is  fused,  and  runs  off 
through  an  aperture  in  the  side  of  the  furnace,  the  production  of  litharge  goes  on  un- 
interruptedly unt'l  all  the  lead  is  removed.  The  button  of  silver  is  again  fused  in  a 
smaller  furnace,  resting  on  a porous  earthen  dish,  made  with  bone-ashes,  Fig.183. 
called  a test  or  cupel , the  porosity  of  which  is  so  great,  that  it  absorbs  any 
remaining  portions  of  litharge  which  may  be  formed  on  the  silver. 

The  cupel  is  easily  prepared  by  driving  pounded  bone  ashes  into  a small 
brass  mould,  by  means  of  a pestle  (Fig.  183),  struck  forcibly  by  a wooden 
Fig.  181.  mallet.  It  must  then  he  removed  cautiously,  placed  on 
a piece  o'  paper  and  dried.  The  mould  is  open  above 
and  below.  In  the  process  the  cupel  is  placed  in  a muf- 
Jle  (Fig.  184),  which  is  made  of  me  clay  used  for  cruci- 
bles,  arched  above  and  closed  at  every  side  except  in  r "1 
front,  so  that  it  may  be  exposed  to  a high  temperature,  7 — ' 

and  air  be  at  the  same  time  admitted.  The  cupel  in  which  is  the 


Oxide  of  Silver . 


309 


Some  of  the  silver  ores,  especially  the  sulphurets,  are  reduced  by  Sect,  vit. 
amalgamation.  These  ores,  when  washed  and  ground,  are  mixed  Amalga- 
wiih  a portion  of  common  salt  and  roasted;  then  powdered  and  mation. 
mixed  by  agitation  with  mercury,  and  the  amalgam  thus  formed  is 
distilled.* 

1241.  The  only  pure  acids  that  act  upon  silver,  are  the  sulphuric  Action  of 
and  nitric,  the  latter  is  its  proper  solvent,  forming  with  its  oxide  a salt,  acicls- 
which,  after  fusion,  is  known  as  lunar  caustic, 

1242.  Oxide  of  Silver , Ag-f-O,  Ag,  or  AgO,  108  1 eq.  silver  -j-  Oxide. 

8 1 eq.  oxy.  ==  116  equiv.,  may  be  procured  by  mixing  a solution  of 
pure  baryta  with  nitrate  of  oxide  of  silver  dissolved  in  water.  It  is 

of  a brown  colour,  insoluble  in  water,  and  is  completely  reduced  by 
a red  heat. 

1243.  Silver  is  separated  from  its  solution  in  nitric  acid  by  pure  Action  of 
alkalies  and  alkaline  earths  as  the  brown  oxide,  which  is  redissolved  alkalies, 
by  ammonia  in  excess;  by  alkaline  carbonates  as  a white  carbonate,  c’ 
soluble  in  an  excess  of  carbonate  of  ammonia  ; as  a dark  brown  sul- 
phuret  by  hydrosulphuric  acid  ; and  as  a white  curdy  chloride  of 
silver,  which  is  turned  violet  by  light  and  is  very  soluble  in  ammonia, 

by  hydrochloric  acid  or  any  soluble  chloride.  By  the  last  character, 
silver  may  be  both  distinguished  and  separated  from  other  metallic 
bodies. 

1244.  Silver  is  precipitated  in  the  metallic  state  by  most  other  Arbor  Di- 
metals. When  mercury  is  employed  the  precipitation  is  very  slow,  an8e’ 
and  produces  a peculiar  symmetrical  arrangement,  called  the  arbor 


lead  and  silver,  is  placed  in  the  muffle,  in  the  cupelling  furnace.  (Fig. 

185.)  This  furnace  has  an  opening  in  one  of  its  sides  to  receive  the 
muffle. 

This  is  an  important  process  and  much  used  by  refiners  and  assay- 
ers  in  the  analysis  of  alloyed  silver.  Supposing  that  an  alloy  of  silver 
and  copper  is  to  be  assayed,  or  analyzed,  by  cupellation,  the  lollowmg 
is  the  mode  of  proceeding. 

A clean  piece  of  the  metal,  weighing  about  30  grains,  is  laminated, 
and  accurately  weighed  in  a very  sensible  balance.  It  is  then  wrapped  up  in  the  re- 
quisite quantity  of  sheet  lead,  (pure  and  reduced  from  litharge,)  and  placed  upon  a 
small  cupel , or  shallow  crucible,  made  of  bone  earth,  which  has  been  previously 
heated.  The  whole  is  then  placed  under  the  muffle,  heated  to  bright  redness ; the 
metals  melt,  and  by  the  action  of  the  air  which  plays  over  the  hot  surface,  the'jead 
and  copper  are  oxidized  and  absorbed  by  the  cupel,  and  a button  of  pure  silver  ulti- 
mately remains,  the  completion  of  the  pyocess  being  judged  of  by  the  cessation  of  the 
oxidation  and  motion  upon  the  surface  of  the  globule,  and  by  the  very  brilliant  appear- 
ance assumed  by  the  silver  when  the  oxidation  of  its  alloy  ceases.  The  button  of 
pure  metal  is  then  suffered  to  cool  gradually,  and  its  loss  of  weight  will  be  equivalent 
to  the  weight  of  the  alloy,  which  has  been  separated  by  oxidation. 

To  perform  this  process  with  accuracy,  many  precautions  are  requisite,  and  nothing 
but  practice  can  teach  these,  so  as  to  enable  the  operator  to  gain  certain  results.  A 
muffle  10  inches  in  length,  5 broad,  and  about  4^  nigh,  answers  for  most  operations. 
It  should  never  be  exposed  suddenly  to  a strong  heat,  as  it  is  very  apt  to  be  cracked  ; 
the  fire  should  also  be  raised  very  gradually,  at  first  with  little  more  than  may  prevent 
it  from  going  out.  The  fuel  is  introduced  from  an  opening  above,  and  care  must  be 
taken  not  to  allow  any  of  it  to  fall  directly  upon  the  muffle.  The  bottom  should  rest 
on  a fire  brick,  and  its  sides  be  at  least  2 inches  from  the  walls  of  the  furnace. 

*The  old  process  of  eliquation  is  now  scarcely  used  5 it  consisted  in  fusing  alloys 
of  copper  and  silver  with  lead  ; this  triple  alloy  was  cast  into  round  masses  which 
were  set  in  a proper  furnace  upon  an  inclined  plane  of  iron  with  a small  channel  groov- 
ed out,  and  heated  red-hot,  during  which  the  lead  melted  out,  and  in  consequence  of 
its  attraction  for  silver,  carrried  that  metal  with  it,  the  copper  being  left  behind  in  a 
reddish-black  spongy  mass.* 


* Aikin’e  Diet.  art.  Silver, 


310 


Chap  IV. 


How  made. 


Fulmina- 
ting silver. 


Process. 


Caution. 


Chloride. 


Effect  of 
light. 


Metals — Silver. 

Diance.  It  was  first  remarked  by  Lemery.  To  obtain  this  crystal- 
lization in  its  most  perfect  state,  the  solution  should  contain  a little 
mercury,  and  the  mercury  put  into  it  should  be  alloyed  with  a little 
silver. 

Make  an  amalgam,  without  heat,  of  four  drachms  of  silver  leaf  with  two  drachms 
of  mercury.  Dissolve  the  amalgam  in  four  ounces  or  a sufficient  quantity  of  pure 
nitric  acid  of  a moderate  strength  ) dilute  this  solution  in  about  a pound  and  a 
half  of  distilled  water ; agitate  the  mixture,  and  preserve  it  for  use  in  a glass  bottle 
with  a ground  stopper.  When  this  preparation  is  to  be  used,  the  quantity  of  one 
ounce  is  put  into  a phial,  and  the  size  of  a pea  of  amalgam  of  gold,  or  silver,  as 
soft  as  butter,  is  to  be  added  ; after  which  the  vessel  must  be  left  at  rest.  Soon 
afterwards,  small  filaments  appear  to  issue  out  of  the  ball  of  amalgam,  which  in- 
crease and  shoot  out  branches  in  the  form  of  shrubs.  U.  703.  According  to 
Proust  all  that  is  required  is  to  throw  mercury  into  nitrate  of  silver  very  much 
diluted. 

1245.  When  oxide  of  silver,  recently  precipitated  by  baryta  or 
lime-water,  and  separated  from  adhering  moisture  by  bibulous  paper, 
is  left  in  contact  for  ten  or  twelve  hours  with  a strong  solution  of 
ammonia,  the  greater  part  of  it  is  dissolved  ; but  a black  powder  re- 
mains which  detonates  violently  from  heat  or  percussion.  This 
substance,  which  was  discovered  by  Berthollet,#  appears  to  be  a 
compound  of  ammonia  and  oxide  of  silver ; for  the  products  of  its 
detonation  are  metallic  silver,  water,  and  nitrogen  gas. 

Precipitate  nitrate  of  silver  by  lime-water,  and  thoroughly  edulcorate  and  dry 
the  precipitate.  Let  this  be  afterward  put  into  a vessel  of  the  purest  liquid  am- 
monia, in  which  it  may  remain  for  ten  or  twelve  hours.  It  will  then  assume  the 
form  of  a black  powder,  from  which  the  fluid  is  to  be  decanted,  and  the  black 
substance  left  to  dry  in  the  air. 

This  is  the  celebrated  compound  termed  fulminating  silver , which 
explodes  with  the  gentlest  heat,  and  even  with  the  slightest  friction. 

1246.  It  should  be  made  in  very  small  quantity  at  a time,  and 
dried  spontaneously  in  the  air.t  When  once  prepared,  no  attempt 
must  be  made  to  enclose  it  in  a bottle,  and  it  must  be  left  undisturbed 
in  the  vessel  in  which  it  was  dried.  Great  caution  is  necessary  in 
the  preparation  of  this  substance,  for  in  making  experiments  on  it 
several  fatal  accidents  have  been  produced  by  indiscretion  in  its  use. 
It  even  explodes,  when  moist,  on  the  gentlest  friction. t 

The  liquid  when  gently  heated,  affords  a still  more  dangerous 
compound.  Another  detonating  compound,  less  dangerous,  may  be 
prepared  by  dissolving  silver  in  nitric  acid,  and  adding  the  solution 
to  alcohol.  It  is  this  which  is  used  in  the  little  balls  known  by  the 
name  of  torpedoes  A 

1247.  Chloride  of  Silver , Ag+Cl,  or  AgCl,  10S  1 eq.  silver -|-  35.42 
1 eq.  chlor.  = 143.42  equiv.,  occurs  in  nature  and  is  the  horn  silver 
of  mineralogists.  It  is  generated  when  silver  is  heated  in  chlorine 
gas,  arid  may  be  prepared  conveniently  by  mixing  hydrochloric  acid, 
or  any  soluble  chloride,  with  a solution  of  nitrate  of  oxide  of  silver. 
As  formed  by  precipitation  it  is  quite  white  ; but  by  exposure  to  the 


* Ann.  de  Chim.  i. 

t The  student  cannot  be  too  careful  in  preparing  this  dangerous  substance,  which 
has  caused  several  fatal  accidents.  See  Bruce’s  Min . Jour.,  i.  j and  for  details  Silli- 
man’s  Chen .,  ii.  336. 

*See  Count  Rumford’s  papers,  Phil.  Trans.,  1798. 

§For  processes  see  Silliman’s  Chem .,  ii. 


Alloys  of  Silver.  311 

direct  solar  rays  it  becomes  violet,  and  almost  black,  in  the  course  of  Sect,  vil 
a few  minutes ; and  a similar  effect  is  slowly  produced  by  diffused 
day-light.^  According  to  Berthollet,  the  dark  colour  is  owing  to  se- 
paration of  oxide  of  silver.! 

1248.  It  is  insoluble  in  water,  and  is  dissolved  very  sparingly  by  Of  acids, 
the  strongest  acids  ; but  it  is  soluble  in  ammonia.  Hyposulphurous 

acid  likewise  dissolves  it.  At  about  500°  it  fuses,  and  forms  a semi- 
transparent horny  mass  on  cooling,  which  has  a density  of  5.524.  It 
bears  any  degree  of  heat,  or  even  the  combined  action  of  pure 
charcoal  and  heat,  without  decomposition  ; but  hydrogen  gas  decom- 
poses it  readily. 

1249.  Chloride  of  silver  is  very  soluble  in  ammonia,  by  which  it  Action  of 
is  usefully  distinguished  from  some  other  chlorides,  which,  like  it, ammonia* 
are  white,  and  formed  by  precipitation.! 

1250.  As  chloride  of  silver  is  insoluble  in  water,  and  very  readily  Uses, 
formed,  it  is  often  employed  in  analysis,  as  a means  of  ascertaining 

the  proportion  of  chlorine  present  in  various  compounds. § 

1251.  Sulphuret  of  Silver.  Ag+S,  or  AgS,  108  1 eq.  silver  Sulphuret. 
+ 16.11  eq.  sulph.  = 124.1  equiv.  Silver  has  a strong  affinity 

for  sulphur.  This  metal  tarnishes  rapidly  when  exposed  to  an  at- 
mosphere containing  hydrosulphuric  acid  gas,  owing  to  the  forma- 
tion of  a sulphuret.  On  transmitting  a current  of  this  gas  through 
a solution  of  lunar  caustic,  a dark  brown  precipitate  subsides,  which 
is  a sulphuret  of  silver.  The  silver  glance  of  mineralogists  is  a 
similar  compound,  and  the  same  sulphuret  may  be  prepared  by 
heating  thin  plates  of  silver  with  alternate  layers  of  sulphur.  This 
sulphuret  is  remarkable  for  being  soft  and  even  malleable.il 

1252.  Alloys  of  Silver.  Silver  unites  with  most  other  metals,  Alloys, 
and  suffers  greatly  in  malleability  and  ductility  by  their  presence. 

When  silver  and  steel  are  fused  together,  an  alloy  is  formed,  which 
appears  perfect  while  in  fusion,  but  globules  of  silver  exude  from  it 

on  cooling,  which  shows  the  weak  attraction  of  the  metals.  At  a 
very  high  temperature  the  greater  part  of  the  silver  evaporates,  but 
a portion  equal  to  about  1 in  500  remains,  forming  a perfect  alloy, 
admirably  adapted  to  the  formation  of  cutting  instruments. IT 

1253.  Silver  readily  combines  with  zinc  and  tin,  forming  brittle 
alloys.  The  alloy  of  silver  with  copper  is  of  the  most  importance,  as 
it  constitutes  plate  and  coin.  By  the  addition  of  a small  proportion 
of  copper  to  silver,  the  metal  is  rendered  harder  and  more  sonorous, 


* Advantage  has  been  taken  of  this  in  obtaining  copies  of  paintings,  engravings, 

&c.,  see  Talbot  on  Photogenic  Drawing , in  Lond.  and  Edin.  Philos.  Jour.  xiv.  197. 

t Stat.  Chim.  vol.  i.  p.  195. 

tWe  should  be  cautious  in  applying  heat  to  the  ammoniacal  solution,  as  it  some- 
times forms  a fulminating  precipitate. 

§In  these  cases  some  excess  of  the  precipitant  should  be  used,  and  the  precipitate  CircnmetAnces 
allowed  to  subside  previous  to  separating  it  upon  the  filter;  if  the  supernatant  li-  u),rbeaa1uend«d* 
quor  become  perfectly  clear,  the  whole  of  the  silver  has  fallen  ; if  it  remain  opalescent,  t0- 
a portion  is  probably  retained.  When  the  precipitate  remains  long  suspended,  its 
deposition  may  be  accelerated  by  warmth,  or  by  adding  a little  nitric  acid.  The  chlo- 
ride in  these  cases  should  be  perfectly  dried  in  a silver  crucible,  up  to  incipient 
fusion.  B.  ii.  180. 

||  Iodide  of  Silver.  Ag-4-I,  or  Agl,  1081  eq.  silver-)- 126.3  1 eq.  iodine  = 234.3  equiv. 

TT  Stoddart  and  Faraday,  on  the  Alloys  of  Steel.  Quart.  Jour.  ix.  5 Bost.  Jour . 


312 


Metals — Gold. 


Chap  IV. 


Silvering 
for  dials. 


Native 

gold. 


Separation 
or  quarta- 
tion. 


Method  of 
obtaining 
pure  gold. 


Characters. 


Malleabili- 

ty- 


while  its  colour  is  scarcely  impaired.  With  lead  the  alloy  is  gray 
and  brittle,  as  also  with  antimony,  bismuth,  cobalt,  and  arsenic.^ 

1254.  Amalgam  of  silver  is  sometimes  employed  for  plating ; it 
is  applied  to  the  surface  of  copper,  and  the  mercury  being  evaporated 
by  heat,  the  remaining  silver  is  burnished.  The  better  kind  of 
plating,  however  is  performed  by  the  application  of  a plate  of  silver 
to  the  surface  of  the  copper,  which  is  afterwards  beaten  or  drawn 
out. 

1255.  A mixture  of  chloride  of  silver,  chalk,  and  pearlash,  is  em- 
ployed for  silvering  brass  ; the  metal  is  rendered  very  clean,  and  the 
above  mixture  moistened  with  water  rubbed  upon  its  surface.  In 
this  way  thermometer  scales  and  clock  dials  are  usually  silvered. 

Gold. 

• Symb.  Au  Equiv.  199.2 

1256.  Gold  occurs  in  nature  in  a metallic  state,  alloyed  with  a 
little  silver  or  copper,  and  in  this  state  is  called  native  gold.  Its  co- 
lour is  various  shades  of  yellow  ; its  forms  are  massive,  ramose,  and 
crystallized  in  cubes  and  octohedra.  Large  quantities  of  this  metal 
are  collected  in  alluvial  soils  and  in  the  beds  of  certain  rivers,  more 
especially  those  of  the  west  coast  of  Africa  and  Peru,  Brazil  and 
Mexico.  It  is  found  in  various  parts  of  Europe,  in  the  Uralian 
mountains,  and  in  North  America. t 

1257.  Gold  is  generally  separated  by  amalgamation  and  cupella- 
tion.  The  best  mode  is  by  fusing  the  gold  with  so  much  silver,  that 
the  former  may  constitute  one  fourth  of  the  mass;  nitric  acid  will 
then  dissolve  all  the  silver  and  leave  the  gold.  This  process  is 
termed  quartation. 

1258.  Gold  may  be  obtained  pure  by  dissolving  standard  gold  in 
nitro-hydrochloric  acid, 4 evaporating  the  solution  to  dryness,  re-dis- 
solving  the  dry  mass  in  distilled  water,  filtering,  and  adding  to  it  a 
solution  of  sulphate  of  protoxide  of  iron  ; a black  powder  falls,  which, 
after  having  been  washed  with  dilute  hydrochloric  acid  and  distilled 
water,  affords  on  fusion  a button  of  pure  gold. 

1259.  Gold  is  of  a deep  yellow  colour.  It  melts  at  a bright  red 
heat,  2016°  Daniell,  and  when  in  fusion  appears  of  a brilliant  green 
colour.  Its  specific  gravity  varies  a little  according  to  the  mechani- 
cal processes  which  it  has  undergone ; but  it  may  be  stated  on  the 
average  at  19.257. 

1260.  Gold  is  so  malleable  that  it  may  be  extended  into  leaves 

which  do  not  exceed  of  an  inch  in  thickness.  It  is  also  very 

* The  standard  silver  of  Great  Britain  consists  of  ll^y  of  pure  silver,  and  cop- 
per. A pound  troy  therefore  is  composed  of  11  oz.  2 dwts.  pure  silver,  and  13  dwts. 
of  copper,  and  it  is  coined  into  66  shillings.  B. 

The  standard  silver  of  the  United  States  is  such  that  of  1000  parts  by  weight,  900 
are  pure  and  100  alloy  j the  alloy  being  of  copper.  The  dollar  weighs  412£  grs.,  the 
dime  4 If  grs. 

t For  an  account  of  the  gold  mines  of  North  Carolina  see  Amer.  Jour,  of  Sci.  iv. 
5.  The  gold  received  at  the  United  States’  mint  from  N.  Carolina,  in  1836,  amounted 
to  148,100  dollars  in  value,  and  that  from  all  the  workings  in  United  Stales  to  467,000 
dollars. 

4 Composed  of  two  measures  hydrochloric  and  one  of  nitric  acid. 


Fulminating  Gold . 313 

ductile  and  considerably  tenacious  ; for  a wire  only  °f  an  inch  Sect,  vii. 
in  diameter  will  sustain  a weight  of  150  lbs. 

1261.  It  shows  no  tendency  to  unite  to  oxygen  even  when  exposed  Effect  of 
to  its  action  in  a state  of  fusion ; but  if  an  electric  discharge  be  electricity» 
passed  through  a very  fine  wire  of  gold,  a purple  powder  is  pro- 
duced, which  has  been  considered  as  an  oxide.  Chlorine  appears  to  Of  chlorine, 
be  the  active  agent  in  dissolving  gold. 

1262.  Protoxide  of  Gold,  Au-|-0,  Au,  or  AuO,  199.2  1 eq.  gold  Protoxide, 
-f-  8 1 eq.  oxy.  .=  207.2  equiv.,  is  obtained  by  the  action  of  a cold 
solution  of  potassa  on  the  protochloride.  It  is  precipitated  of  a 

green  colour.  It  undergoes  spontaneous  change  into  metallic  gold 
and  teroxide.  The  purple  oxide  formed  by  the  combustion  of  gold 
is  supposed  to  be  the  binoxide .* 

1263.  Teroxide  of  Gold,  Au-j-30,  Au,  or  AuO3,  199.2  1 eq.  gold.  Teroxide. 
+ 24  3 eq.  oxy.  = 223.2  equiv.,  the  only  well  known  oxide  of  gold, 

may  be  prepared  by  the  following  process  : 

Dissolve  1 part  of  gold  in  the  usual  way,  render  it  quite  neutral  by  evapora-  Process, 
don,  and  redissolve  in  12  parts  of  water  : to  the  solution  add  1 part  of  carbonate 
of  potassa  dissolved  in  twice  its  weight  of  water,  and  digest  at  about  170°.  Car- 
bonic acid  gradually  escapes,  and  the  hydrated  teroxide  of  a brownish-red  colour 
subsides.  After  being  well  washed  it  is  dissolved  in  colourless  nitric  acid  of  sp. 
gr»  1.4,  and  the  solution  decomposed  by  admixture  with  water. 

The  hydrated  teroxide  is  thus  obtained  quite  pure,  and  is  rendered 
anhydrous  by  a temperature  of  212°  F. 

1264.  Teroxide  of  gold  is  yellow  in  the  state  of  hydrate,  and  Properties, 
nearly  black  when  anhydrous,  is  insoluble  in  water,  and  completely 
decomposed  by  solar  light  or  a red  heat.  It  combines  with  alkaline 

bases,  such  as  potassa  and  baryta,  apparently  forming  regular  salts, 
in  which  it  acts  the  part  of  a weak  acid.  This  property,  induced  Aurates 
Pelletier  to  propose  for  it  the  name  of  auric  acid,  its  compounds 
with  alkalies  being  called  aurates. t 

1265.  When  recently  precipitated  teroxide  of  gold  is  kept  in  Action  of 
strong  ammonia  for  about  a day,  a detonating  compound  of  a deep  Ammonia, 
olive  colour  is  generated.  According  to  the  analysis  of  Dumas,  its 
elements  are  in  the  ratio  of  one  equivalent  of  gold,  two  of  nitrogen, 

six  of  hydrogen,  and  three  of  oxygen.  With  regard  to  the  mode  in 
which  these  elements  are  arranged,  different  opinions  may  be  formed. 

It  appears  most  simple  to  consider  it  as  a diaurate  of  ammonia,  ex- 
pressed by  the  formula  2(3H-f-N)~|~Au03.  t.  387. 

1266.  The  compound  known  as  Fulminating  Gold,  is  similar  to  Fulmina- 
the  above,  and  is  obtained  by  digesting  terchloride  of  gold  with  an  ting  soldl 
excess  of  ammonia. 

To  obtain  this  compound  add  a solution  of  ammonia  in  water,  or  the  pure  process  for„ 
liquid  ammonia,  to  the  diluted  chloride  ; a precipitate  will  appear,  which  will  be 
re-dissolved  if  too  much  alkali  be  used.  Let  the  liquor  be  filtered  and  wash  the 
sediment  which  remains  on  the  filter  with  several  portions  of  warm  water.  Dry 
it  by  exposure  to  the  air,  without  any  artificial  heat,  and  preserve  it  in  a wide 
mouthed  bottle,  in  small  packets  of  paper,  closed,  not  with  a glass  stopper,  but 
merely  by  a cork. 

A small  portion  of  this  powder,  less  than  a grain  in  weight,  being 


* Binoxide  of  Gold.  Au+20,  or  AuO2,  199.2  1 eq.  gold  4-  16  2 eq.  oxy.  = 215.2 
equiv.  t An.  de  Ch . et  de  Ph.  xv. 

40 


314 


Metals — Gold. 


Chap.  IV. 


Chlorides. 


Terchlo- 

ride, 


Pure  gold 
from. 


Ethereal 

solution. 


Action  of 
tin. 


placed  on  the  point  of  a knife  and  held  over  a lamp,  detonates  vio- 
lently. The  precise  temperature  which  is  required  is  not  known, 
but  it  appears  to  be  about  290°  F.  At  the  moment  of  explosion,  a 
transient  flash  is  observed.  Two  or  three  grains,  exploded  on  a 
pretty  strong  sheet  of  copper,  will  force  a hole  through  it.  Neither 
electricity  nor  a spark  from  the  flint  and  steel  are  sufficient  to  occa- 
sion its  detonation  ; but  the  slightest  friction  explodes  it,  and  serious 
accidents  have  happened  from  this  cause. 

1267.  Chlorides  of  Gold.  The  terchloride  is  obtained  in  ruby-red 
crystals  by  concentrating  the  solution  of  gold.  It  is  soluble  in  alco- 
hol and  ether,  the  latter  removing  it  from  the  aqueous  solution.  It 
loses  chlorine  at  about  400°  F.,  and  is  changed  into  a mixture  of 
protochloride * and  terchloride,  soluble  in  water. 

1268.  Terchloride  of  Gold , Au-f-3Cl,  or  AuCl3,  199.2  1 eq.  gold 
-f-  106.26  3 eq.  chlor.  = 305.46  equiv.,  is  the  usual  and  most  con- 
venient form  of  obtaining  a solution  of  gold.  On  adding  to  the  so- 
lution sulphate  of  protoxide  of  iron,  a brown  precipitate  ensues, 
which  is  gold  in  very  fine  division,  and  the  solution  contains  tersul- 
phate  of  sesquioxide,  and  sesquichloride  of  iron.  The  action  is  such 
that 

G eq.  sulphate  of  protoxide  of  iron  . . 6(Fe-}-S) 

and  1 eq.  terchloride  of  gold Au-f-oCl 


yield 

2 eq.  tersulphate  of  sesquioxide  of  iron 
1 eq.  sesquichloride  of  iron 
and  1 eq.  gold  ..... 


2(Fe-f3S) 

2Fe+3Cl 

Au 


1269.  The  precipitate,  washed  with  dilute  hydrochloric  acid  to  se- 
parate adhering  iron,  is  gold  in  a state  of  perfect  purity.  A similar 
reduction  is  effected  by  most  of  the  metals.  When  a piece  of  char- 
coal is  immersed  in  a solution  of  gold,  and  exposed  to  the  direct  solar 
rays,  its  surface  acquires  a coating  of  metallic  gold,  and  ribands  may 
be  gilded  by  moistening  them  with  a dilute  solution  of  gold,  and  ex- 
posing them  to  a current  of  hydrogen  or  phosphuretted  hydrogen 
gas. 

1270.  When  a strong  aqueous  solution  of  gold  is  shaken  in  a 
phial  with  an  equal  volume  of  pure  ether,  two  fluids  result,  the 
lighter  of  which  is  an  ethereal  solution  of  gold.  From  this  liquid 
flakes  of  metal  are  deposited  on  standing,  especially  by  exposure  to 
light,  and  substances  moistened  with  it  receive  a coating  of  metallic 
gold.t 

1271.  When  protochloride  of  tin  is  added  to  a dilute  aqueous  so- 
lution of  gold,  a purple-coloured  precipitate,  called  the  purple  of 
Cassius , is  thrown  down  ; and  the  same  substance  may  be  prepared 
by  fusing  together  150  parts  of  silver,  20  of  gold,  and  35.1  of  tin, 
and  acting  on  the  alloy  with  nitric  acid,  which  dissolves  out  the  sil- 
ver and  leaves  a purple  residue,  containing  the  tin  and  gold  which 
were  employed.  To  prevent  the  oxidation  of  the  tin  during  fusion, 
the  three  metals  should  be  projected  into  a red-hot  black-lead  cruci- 
ble, which  contains  a little  melted  borax. 


* Protochloride  of  Gold.  Au-j-Cl,  or  AuCl,  199.2  1 eq.  gold  -|-  35.42  l eq.  chlor.  = 
234.62  equiv. 

+ $ee  an  Essay  on  Combustion  by  Mte  Fulhome,  and  a paper  by  Rumford  is  the 
PkU.  7Vun».  Ayr  1798. 


315 


Alloys  of  Gold . 

1272.  When  the  powder  of  Cassius  is  fused  with  vitreous  sub-  Sect,  vii. 
stances,  such  as  flint-glass,  or  a mixture  of  sand  and  borax,  it  forms  Purple  of 
with  them  a purple  enamel,  which  is  employed  in  giving  pink  co- ^assius* 
[ours  to  porcelain.  The  essential  cause  of  the  colour  is  probably  a Uses* 
compound  of  the  purple  or  supposed  binoxide  of  gold  with  earthy 
natters,  similar  to  the  enamel  formed  by  glass  and  oxide  of  silver.* 

1273.  Alloys  of  GoldA  The  alloy  of  gold  and  iron  is  malleable  With  po- 
ind ductile,  and  harder  than  gold,  its  colour  dull  white,  and  its  spe-  ^®slum> 
fific  gravity  16.885.  The  metals  expand  by  union. 

1274.  With  zinc  the  compound  is  brittle  and  brass-coloured.  With  zinc. 
Specific  gravity  16.937.  The  metals  contract  a little  in  uniting. 

The  fumes  of  zinc  in  a furnace  containing  fused  gold,  make  it 
brittle. 

1275.  Tin  forms  a whitish  alloy,  brittle  when  thick,  but  flexible  in  With  tin. 
;hin  pieces.  Specific  gravity  17.307.  There  is  considerable  con- 
;raction.  The  old  chemists  called  tin  diabolus  metallorum,  from  its 
property  of  rendering  gold  brittle,  but  Bingley’s  experiments  quoted 

by  Hatchett,  show  that  of  tin  does  not  render  gold  brittle. 

1276.  The  alloy  of  lead  is  very  brittle  when  that  metal  only  con- With  lead, 
stitues  '^27  of  the  alloy;  even  the  fumes  of  lead  destroy  the  duc- 
tility of  gold.  The  sp.  gravity  is  18.080 ; and  1000  parts  become 

1005. 

1277.  With  copper  (standard  gold)  the  alloy  is  perfectly  ductile  With  cop- 
and  malleable,  but  harder  than  pure  gold,  and  resists  wear  better  per‘ 
than  any  other  alloy  except  that  with  silver.  Its  specific  gravity  is 
17.157.4 

1278.  Arsenic  and  antimony,  when  alloyed  in  very  small  pro- 
portions with  gold,  destroy  its  colour  and  render  it  quite  brittle. 

1279.  The  analysis  of  most  of  the  alloys  of  gold  is  performed  by  ^noysof 
cupellation.  The  triple  alloy  of  gold,  silver,  and  copper,  may  be 
analyzed  by  digesting  it  in  nitric  acid,  which  takes  up  the  silver  and 
copper,  and  leaves  the  gold  in  the  form  of  a black  powder,  which 

may  be  fused  into  a button  and  weighed.  The  silver  may  be  thrown 
down  in  the  state  of  chloride  by  solution  of  common  salt,  and  the 
copper  precipitated  by  iron. 


* Iodides  of  Gold  are  formed  by  the  action  of  iodide  of  potassium  on  the  terchloride 
of  gold. 

Protiodide  of  Gold . Au+I,  or  Aul,  199.2  1 eq.  gold  -1-  126.3  1 eq.  iod.  = 325.5 
equiv. 

Teriodide  of  Gold.  Au+3l,  or  Aul3,  199-2  l eq.  gold  + 378.9  3 eq.  iod.  = 578. 1 
equiv.* 

t A very  curious  series  of  experiments  upon  the  alloys  of  gold  has  been  published 
in  the  Phil.  Trans . for  1803,  by  Hatchett.  See  also  Thomson’s  Inorgi  Chem.,  i 654. 
t The  standard  gold  of  the  United  States  contains  in  1000  parts  by  weight  900  of 

Eure  metal  and  100  alloy  composed  of  copper  and  silver,  the  latter  not  exceeding  one 
alf  of  the  whole  alloy.  The  legal  weight  of  the  American  eagle  is  253  grs  The 
legal  standard  of  the  British  sovereign  is  22  carats  — 916|  thousandths.  Forty 
pounds  Troy  are  made  into  1869  sovereigns,  the  weight  of  each  = 123.2744  grs.  The 
value  of  the  sovereign  in  gold  of  United  States,  should  be  4 .8665.  Numerous  exami- 
nations of  British  gold  at  the  U.  S.  mint  show  that  the  actual  quality  of  the  gold  does 
not  average  more  than  915^,  or  the  average  weight  more  than  122.88  grs.  The  exa- 
mination of  104,960  sovereigns  (the  Smithsonian  legacy)  at  the  mint,  produced  an 

average  of  4-84  T4T  per  sovereign. 

* See  Johnston’s  experiments  in  Phil.  Mag',  and  Ann.  ix.  266. 

TevsUlplturet  of  Chid.  Au-f&S  or  Au83,  1P9.2  1 eq  gold  -f  48. S 3 eq.  suiph.  =>  947.5  equi?. 


316 


Metals — Platinum . 


Chap.  IV. 
Assay. 


Water  gild- 
ing. 


Carats. 


Ores. 


Characters. 


Action  of 
heat  and 
air. 


Spongy 

platinum. 


1280.  The  assay  of  gold  is  more  complicated  than  that  of  silver, 
in  consequence  of  the  high  attraction  which  it  has  for  copper,  and 
which  prevents  its  complete  separation  by  mere  cupellation.  An  al- 
loy, therefore,  of  copper  with  gold,  is  combined  with  a certain  quan- 
tity of  silver,  previous  to  cupellation  ; this  is  then  cupelled  with  lead 
ih  the  usual  way,  and  the  silver  is  afterwards  separated  by  the  ac- 
tion of  nitric  acid.* 

1281.  Mercury  and  gold  combine  with  great  ease,  and  produce  a 
white  amalgam  much  used  in  gilding.  For  this  purpose  the  amal- 
gam is  applied  to  the  surface  of  the  silver;  the  mercury  is  then 
driven  off  by  heat,  and  the  gold  remains  adhering  to  the  silver,  and 
is  burnished.  This  process  is  called  water  gilding. 

1282.  In  gilding  porcelain,  gold  powder  is  generally  employed, 
obtained  by  the  decomposition  of  the  chloride  ; it  is  applied  with  a 
pencil,  and  burnished  after  it  has  been  exposed  to  the  heat  of  the 
porcelain  furnace. 

1283.  The  degree  of  purity  of  gold  is  expressed  by  the  number  of 
parts  of  that  metal,  contained  in  the  24  parts  of  any  mixture.  Thus 
gold,  which  in  24  such  parts  (termed  carats ,)  contains  22  of  the  pure 
metal  is  said  to  be  22  carats  fine.  Absolutely  pure  gold,  using  the 
same  language,  is  24  carats  fine  ; and  gold  alloyed  with  an  equal 
weight  of  another  metal,  12  carats  fine.f 

Platinum. 

Symb.  Pt  Equiv.  98. 8 

1284.  This  valuable  metal  occurs  in  Brazil,  Peru,  and  other  parts 
of  South  America  in  rounded  or  flattened  grains  mingled  with  seve- 
ral other  metals.  In  1826  it  was  discovered  by  Bousingault  in  a 
sienitic  rock  in  the  province  of  Antioquia,  in  South  America,  and 
since  then  it  has  been  found  in  larger  quantity  in  the  Uralian  moun- 
tains. t 

1285.  It  is  a white  metal,  much  resembling  silver,  and  is  the  heaviest 
metal  known ; after  forging  its  density  being  about  21.25,  and  in  the 
state  of  wire  21.5.  It  is  malleable,  and  may  be  drawn  into  wire  the 
diameter  of  which  does  not  exceed  the  two  thousandth  part  of  an 
inch.  It  is  soft,  and  has  the  valuable  property  of  welding.  It  is  a 
less  perfect  conductor  of  heat  than  several  other  metals. § 

1286.  It  is  unaltered  by  the  joint  action  of  heat  and  air ; but 
small  wires  of  it  are  fused  and  burn  in  the  Voltaic  circuit,  and  before 
the  oxyhydrogen  blow-pipe.  No  pure  acids  attack  it.  Its  solvents 
are  chlorine,  or  solutions  that  supply  chlorine,  as  nitrohydrochloric 
acid. 

1287.  Spongy  platinum  has  been  discovered  by  Dobereiner  to  have 


* The  real  quantity  of  gold  or  silver  taken  for  an  assay  is  very  small ; from  18  to  36 
grains,  for  instance,  for  silver,  and  from  6 to  12  for  gold ; whatever  the  quantity  may 
be  it  is  called  the  assay  pound.  The  silver  assay  pound  is  divided  into  12  ounces,  ana 
each  ounce  into  20  pennyweights.  The  gold  assay  pound  is  subdivided  into  24  carats, 
and  each  carat  into  4 assay  grains.  Aiken’s  Dicl .,  art.  Assay. 

t Many  curious  facts  relating  to  the  properties  of  gold,  and  its  uses  in  the  arts,  will 
be  found  m Lewis’s  Phil.  Com.  of  the  Arts. 

J Edin.  Jour,  of  Sci.,  v.  323. 

§ For  many  important  details  respecting  platinum,  see  Wollaston’s  paper  in  Phil. 
Trans .,  1829,  and  Brande’s  Manual , ii.  20C. 


317 


Protochloride  of  Platinum . 

the  remarkable  property  of  causing  the  union  of  oxygen  and  hydro-  Sect,  vn.  , 
gen  gases  (387)  ; and  Dulong  and  Thenard  have  shown  that  the  same 
effect  takes  place,  though  in  a lower  degree,  with  platinum  foil  and 
wire.^ 

1288.  According  to  Faradayf  the  gases  must  be  pure  and  the  pla- 
tinum  free  from  foreign  matters,  pure  water  excepted,  which  is  ef-tions. 
fected  by  fusing  pure  potassa  on  its  surface,  washing,  then  dipping 

the  platinum  in  hot  oil  of  vitriol,  and  again  washing  with  pure 
water. 

1289.  In  this  state  platinum  foil  acts  so  rapidly  at  common  tern-  Action  of. 
peratures  on  oxygen  and  hydrogen  gases  mixed  in  the  ratio  of  1 to 

2,  that  it  often  becomes  red-hot  and  kindles  the  mixture.  Handling 
the  platinum,  wiping  it  with  a towel,  or  exposing  it  to  the  atmos- 
phere for  a few  days,  suffices  to  soil  the  surface  of  the  metal,  and 
thereby  diminish  or  prevent  its  action. 

1290.  These  phenomena  are  supposed  to  result  from  the  concur-  Theory  of. 
ring  influence  of  two  forces,  the  self-repulsive  energy  of  similar 
gaseous  particles,  and  the  adhesive  attraction  exerted  between  them 

and  the  platinum.  Each  gas,  repulsive  to  itself  and  not  repelled  by 
the  platinum,  comes  into  the  most  intimate  contact  with  that  metal, 
and  both  gases  are  so  condensed  upon  its  surface,  that  they  are 
brought  within  the  sphere  of  their  mutual  attraction  and  combine. 

1291.  Protoxide  of  Platinum,  Pt-f-O,  Pt,  or  PtO,  98.8  1 eq.  plat.  Protoxide. 
+ 8 1 eq.  oxy.  ==  106.8  equiv.,  is  prepared  by  digesting  protochlo- 
ride of  platinum  in  a solution  of  pure  potassa,  avoiding  a large  ex- 
cess of  the  alkali,  since  it  dissolves  a portion  of  the  oxide,  and 
thereby  acquires  a green  colour.  In  this  state  it  is  a hydrate  which 

loses  first  its  water  and  then  oxygen  when  heated,  and  dissolves 
slowly  in  acids,  yielding  solutions  of  a brownish-green  tint. 

1292.  Binoxide  of  Platinum . Pt-f-20,  Pt,  or  PtO2,  98.8  1 eq.  Binoxide. 
plat,  -f-  16  2 eq.  oxy.  i==  114.8  equiv.  This  oxide  is  prepared  with 
difficulty.  Berzelius  recommends  that  it  should  be  prepared  by  ex- 
actly decomposing  sulphate  of  binoxide  of  platinum  with  nitrate  of 
baryta,  and  adding  pure  soda  to  the  filtered  solution,  so  as  to  precipi- 
tate about  half  of  the  oxide  ; since  otherwise,  a sub-salt  would  sub- 
side. The  oxide  falls  in  the  form  of  a bulky  hydrate,  of  a yellowish- 
brown  colour  ; it  resembles  rust  of  iron  when  dry,  and  is  nearly 

black  when  rendered  anhydrous. $ 

1293.  Protochloride  of  Platinum.  Pt— |— Cl,  or  PtCl,  98.8  1 eq.  Protochlo- 
plat.  -j-  35.42  1 eq.  chlor.  = 134,22  equiv.  When  the  bichloride  ride- 

is  heated  to  450°,  half  of  its  chlorine  is  expelled,  and  the  protochlo- 
ride of  a greenish-gray  colour  remains.  It  is  insoluble  in  water, 
sulphuric  acid,  and  nitric  acid  ; but  hydrochloric  acid  partially  dis- 
solves it,  yielding  a red  solution.  At  a red-heat  its  chlorine  is  dri- 
ven off,  and  metallic  platinum  is  left.  It  is  dissolved  by  a solution 
of  the  bichloride. 


* Ann.  de  Chim.  et  de  Phys .,  xxiii.  and  xxiv.  + Phil.  Trans.  1834,  part  i. 
t Sesquioxide  of  Platinum.  2PH-30,  or  Pt203,  197.6  2 eq.  plat.  + 24  3 eq  oxy.  = s«aquioxide.  j 
221. 6, equiv.  This  oxide,  of  a gray  colour,  is  prepared  according  to  its  discoverer,  E. 

Davy,  by  heating  fulminating  platinum  with  nitrous  acid ; but  the  nature  of  the  com- 
pound so  formed  has  not  yet  been  decisively  determined.  Phil,  Trans  , 1820. 


318 


Metals — Platinum. 


Solutions 

recognized 


.chap,  iv.  1294.  Bichloride  of  Platinum.  Pt-f-2Cl,  or  PiCP,  98.8  1 eq. 

Bichloride,  plat.  -J-  70.84  2 eq.  chlor.  = 169.64  equiv.  This  chloride  is  ob- 
tained by  evaporating  the  solution  of  platinum  in  nitro-hydrochloric 
acid  to  dryness  at  a very  gentle  heat,  when  it  remains  as  a red  hy- 
drate, which  becomes  brown  when  its  water  is  expelled.  It  is  deli- 
quescent, and  very  soluble  in  water,  alcohol,  and  ether ; its  solution, 
if  free  from  the  chlorides  of  palladium  and  iridium,  being  of  a pure 
yellow  colour.  Its  ethereal  solution  is  decomposed  by  light,  metal- 
lic platinum  being  deposited. 

1295.  A solution  of  platinum  is  recognized  by  the  following  cha- 
racters. When  to  an  alcoholic  or  concentrated  aqueous  solution  of 
the  bichloride,  a solution  of  chloride  of  potassium  is  added,  a crys- 
talline double  chloride  of  a pale  yellow  colour  subsides,  which  is 
insoluble  in  alcohol,  and  sparingly  soluble  in  water  ; at  a red  heat  it 
yields  chlorine  gas,  and  the  .residue  consists  of  metallic  platinum  and 
chloride  of  potassium.  With  a solution  of  hydrochlorate  of  ammo- 
nia a similar  yellow  salt  falls,  which  when  ignited  leaves  pure  pla- 
tinum in  the  form  of  a delicate  spongy  mass,  the  power  of  which  in 
kindling  an  explosive  mixture  of  oxygen  and  hydrogen  gases  has 
already  been  mentioned*  (1287). 

Biniodide.  1296.  Biniodide  of  PlatiJium,  Pt-f-2I,  or  PtP,  98.8  1 eq.  plat,  -f- 
252.6  2 eq.  iod.  = 351.4  equiv.,  prepared  by  the  action  of  iodide  of 
potassium  on  a rather  dilute  solution  of  bichloride  of  platinum.  At 
first  the  liquid  acquires  an  orange-red  and  then  a claret  colour, 
without  any  precipitation  ; but  when  the  solution  is  boiled,  a black 
precipitate  subsides,  which  should  be  washed  with  hot  water  and 
dried  at  a heat  not  exceeding  212°.  This  biniodide  is  a black  pow- 
der, sometimes  crystalline,  is  tasteless  and  inodorous,  insoluble  in 
water,  and  may  be  boiled  in  water  without  change.  By  alcohol  it  is 
sparingly  dissolved,  especially  when  heated.  Acids  act  feebly  upon 
it ; but  it  is  decomposed  by  alkalies  ; and  begins  to  lose  iodine  at 
270°. t 


Protosul- 

phuret. 


Bisulphu- 

ret. 


Fulmina- 

ting. 


1297.  P rotosulphuret  of  Platinum , Pt-j-S,  or  PtS,  9S.8  1 eq. 
plat,  -f-  16.1  1 eq.  sulph.  '=  114.9  equiv.,  is  formed  by  heating  the 
ammoniaeal  chloride  with  half  its  weight  of  sulphur,  until  all  the  sal 
ammoniac  and  excess  of  sulphur  are  expelled. 

1298.  Bisulphuret  of  Platinum , Pt-j-2S,  or  PtS2,  98.S  1 eq.  plat, 
-f-  32.2  2 eq.  sulph.  = 131  equiv.,  is  formed  by  dropping  a solution 
of  bichloride  of  platinum  into  a solution  of  sulphuret  of  potassium,  or 
by  transmitting  hydrosulphuric  acid  gas  into  a solution  of  the  double 
chloride  of  platinum  and  sodium.  It  should  be  dried  in  vacuo. 

1299.  Fulminating  platinum  may  be  prepared  by  the  action  of 
ammonia  in  slight  excess  on  a solution  of  sulphate  of  protoxide  of 
platinum.  When  boiled  in  potassa,  washed  and  dried,  it  was  found 
by  E.  Davy  to  explode  at  about  420°  with  a very  loud  report.^  One 
grain  laid  on  a thin  sheet  of  copper  and  exploded  produces  a report 


* Protiodide  of  Platinum , Pt+I.or  PtI,  98.8  1 eq.  plat.  + 126  3 1 eq.  iod.  =225.1 
equiv.,  prepared  by  digesting  the  protochloride  of  platinum  in  a rather  strong  solution 
ot  iodide  of  potassium,  when  the  protiodide  gradually  appears  in  the  form  a black 
powder,  which  is  insoluble  in  water  and  alcohol  It  is  unchanged  by  the  sulphuric, 
nitric,  and  hydrochloric  acids,  decomposed  by  the  alkalies,  and  at  a red  heat  gives  on 
its  iodine.  t An.  de  Oh.  etdt  PA.,li.  113.  t Phii.  Trans.  lSlf. 


Osmium  and  Iridium . 


319 


louder  than  that  of  a pistol,  and  the  copper  is  deeply  indented.  It  is  Sect,  vn. 
incapable  of  being  exploded  by  percussion. 

1300.  Palladium , Rhodium , Osmium , and  Iridium.  These  metals  Associated 
are  found  associated  in  the  ore  of  platinum,  and  have  been  procured  meta  s‘ 
but  in  small  quantity. 

1301.  Palladium,  Pd,  53.3  eq.,  was  discovered  by  Wollaston  ; it  Palladium, 
resembles  platinum  in  colour  and  lustre;  it  is  ductile  and  malleable; 

its  sp.  gr.  is  11.3  to  118. 

1302.  In  fusibility  it  is  intermediate  between  gold  and  platinum,  Properties, 
and  is  dissipated  in  sparks  when  intensely  heated  by  the  oxy hydro- 
gen blow-pipe.  At  a red  heat  in  oxygen  gas,  its  surface  acquires  a 

fine  blue  colour,  owing  to  superficial  oxidation  ; but  the  increase  of 
weight  is  so  slight  as  not  to  be  appreciated. 

1303.  Palladium  is  oxidized  and  dissolved  by  nitric  acid,  and  even  Action  of 
the  sulphuric  and  hydrochloric  acids  act  upon  it  by  the  aid  of  heat;  acids* 
but  its  proper  solvent  is  nitro-hydrochloric  acid.  Its  protoxide  forms 
beautiful  red-coloured  salts,  from  which  metallic  palladium  is  preci- 
pitated by  sulphate  of  protoxide  of  iron,  and  by  all  the  metals  de- 
scribed in  the  foregoing  sections,  excepting  silver,  gold,  and  pla- 
tinum. 

1304.  Rhodium , R,  52,2  eq.,  was  discovered  by  Wollaston  at  the  Rhodium 
time  he  was  occupied  with  the  discovery  of  palladium.  He  obtained  oblained> 
it  in  the  form  of  a black  powder,  which  requires  the  strongest  heat 

that  can  be  produced  in  a wind  furnace  for  fusion,  and  when  fused 
has  a white  colour  and  metallic  lustre. 

1305.  It  is  brittle,  is  extremely  hard,  and  has  a specific  gravity  of  Properties, 
about  11.  It  attracts  oxygen  at  a red  heat,  a mixture  of  peroxide 

and  protoxide  being  formed.  It  is  not  attacked  by  any  of  the  acids 
when  in  its  pure  state , but  if  alloyed  with  other  metals,  such  as 
copper  or  lead,  it  is  dissolved  by  nitro-hydrochloric  acid,  a circum- 
stance which  accounts  for  its  presence  in  the  solution  of  crude  pla- 
tinum. 

1306.  It  is  oxidized  by  being  ignited  either  with  nitre,  or  bisul-  Oxidized, 
phate  of  potassa.  When  heated  with  the  latter,  sulphurous  acid  gas 

is  evolved,  and  a double  sulphate  of  peroxide  of  rhodium  and  potassa 
is  generated,  which  dissolves  readily  in  hot  water,  and  yields  a yel- 
low solution.  The  presence  of  rhodium  in  platinum,  iridium,  and 
osmium  may  thus  be  detected,  and  by  repeated  fusion  a perfect  se- 
paration be  accomplished-^  Most  of  its  salts  are  either  red  or 
yellow. 

1307.  Osmium  and  Iridium.  Os,  99.7  eq.  These  metals  were  Osmium 
discovered  by  Tennant  in  the  year  1803, t and  the  discovery  of  iridi-  Indl" 
um  was  made  about  the  same  time  by  Descotils  in  France.  Wol- 
laston detected  them  as  an  alloy  in  the  black  powder  accompanying 

the  ore  of  platinum.  Osmium  acquires  a metallic  lustre  by  friction  ; 
its  sp.  gr.  is  7 to  10.  It  takes  fire  when  heated  in  the  open  air,  and 
is  readily  oxidized  and  dissolved  by  fuming  nitric  acid. 

1308.  The  highest  stage  of  oxidation  of  Os.  is  the  volatile  compound  Osmicacid, 
Osmic  Acid,  Os+40,  or  OsO4,  99.7  1 eq.  osmium  + 32  4 eq.  oxy. 

= 131.7  equiv.,  which  is  the  product  of  the  oxidation  of  osmium  by 


* Berzelius, 


t Phil.  Trans.  1804. 


320 


Salts . 


Chap.  V. 


Iridium. 


Latanium, 


Oxide  of, 


Salts  of. 


Application 
of  the  term 
salt* 

ft 


Orders. 


Oxysalts, 

what. 


. acids,  by  combustion,  or  by  fusion  with  nitre  or  alkalies.  Its  vapour 
is  very  acrid,  exciting  cough,  irritating  the  eyes,  and  producing  a 
copious  flow  of  saliva;  its  odour  is  disagreeable  and  pungent,  some- 
what like  that  of  chlorine,  hence  the  name  osmium  from  oo/tTj,  odour. 
With  infusion  of  gall  nuts  it  gives  a purple  solution,  which  after- 
wards acquires  a deep  blue  lint,  a delicate  test  of  the  acid. 

1309.  Iridium  is  a brittle  metal,  apt  to  fall  to  powder  when  burnished, 
but  with  care  may  be  polished  and  then  resembles  platinum.  It  is 
the  most  infusible  of  all  metals  ; sp.  gr.  15.8629  ; equiv.  98.8.  It 
forms  with  oxygen  4 oxides,  and  with  chlorine  4 chlorides. 

1310. $These  metals  combine  with  oxygen,  chlorine,  and  sulphur, 
for  an  account  of  the  compounds  the  student  is  referred  to  Turner’s 
Elements,  and  Brande’s  Manual. 

1311.  Latanium.  In  submitting  the  cerite  of  Bastnaes  to  exami- 
nation Mosander  has  very  recently  obtained  this  new  metal,  and 
which  was  named  from  its  being,  as  it  were,  hidden  by  the  cerium. 

It  was  prepared  by  calcining  the  nitrate  of  cerium  mixed  with  nitrate 
of  latanium.  The  oxide  of  cerium  loses  its  solubility  in  weak  acids  ; j 
and  the  oxide  of  latanium,  which  is  a very  strong  base,  may  be  sepa- 
rated by  nitric  acid,  mixed  with  100  parts  of  water. 

1312.  The  oxide  is  of  a brick-red  colour,  owing  to  the  presence  of 
oxide  of  cerium ; it  is  converted  by  hot  water  into  a white  hydrate 
which  restores  the  blue  colour  of  litmus  paper:  it  is  rapidly  dis- 
solved by  dilute  acids,  and  when  used  in  excess  is  converted  into 
a sub-salt. 

1313.  Its  salts  have  an  astringent  taste,  without  any  mixture  of 
sweetness ; and  the  crystals  are  of  a rose-red  colour.  The  atomic  , 
weight  of  latanium  is  smaller  than  that  of  cerium.* 


CHAPTER  V. 

Section  1.  Salts. 

1314.  The  term  salt  has  been  applied  to  a very  extensive  range  of 
compounds,  where  acids  are  combined  with  oxides,  or  other  com- 
pounds having  similar  properties.  The  oxide  or  other  substance 
united  with  the  acid  is  called  a base  or  salifiable  base.  Each  acid, 
with  few  exceptions,  is  capable  of-uniting  with  every  alkaline  base, 
and  frequently  in  two  or  more  proportions. 

1315.  The  class  of  salts  has  been  divided  into  four  orders  (330), 
and  many  of  their  characters  have  been  already  described. t 

Order  lsL  Oxysalts. 

1316.  Of  the  common  salts,  a large  proportion  contain  oxygen 
both  in  the  acid  and  in  the  base,  thus  in  the  phosphate  of  soda  it  is 
associated  with  phosphorus  in  the  phosphoric  acid,  and  with  sodium 
in  the  soda,  and  hence  such  are  termed  oxysalts. 


* Lond.  and  Edin.  Phil.  Mag.,  May,  1839. 

t Graham  has  been  led  to  the  conclusion  that  all  salts  are  neutral  in  their  constitu- 
tion,  with  the  exception  of  certain  classes.  See  Turner,  403.  Thomson  has  divided 
the  salts  into  nine  classes.  See  Chem.  of  Inorg.  Bodiet , vol.  ii.  378. 


Sulphates . 321 

1317.  Those  salts  which  consist  of  the  same  acid  united  with  dif-  Sect,  i. 
ferent  salifiable  bases,  possess  certain  characters  in  common,  and 

may  be  considered  as  constituting  one  family. 

The  combination  of  salts  with  one  another  gives  rise  to  compounds  Double 
which  were  formerly  called  triple  salts ; but  the  term  double  salt,  salts, 
proposed  by  Berzelius,  gives  a more  correct  idea  of  their  nature  and 
constitution.  These  salts  may  be  composed  of  one  acid  and  two 
bases,  of  two  acids  and  one  base,  and  of  two  different  acids  and  two 
different  bases.  Most  of  the  double  salts  hitherto  examined  consist 
of  the  same  acid  and  two  different  bases. 

1318.  All  the  powerful  alkaline  bases,  excepting  ammonia,  are  the 
protoxides  of  an  electro-positive  metal,  such  as  potassium,  barium 
or  iron  ; so  that  if  M represent  an  eq.  of  any  one  of  those  metals 
M-j-O,  or  MO  is  the  strongest  alkaline  base,  and  often  the  only  one 
which  that  metal  can  form.  A single  eq.  of  acid  neutralizes  MO, 
forming  with  it  a neutral  salt.  Thus,  indicating  an  equivalent  of 
sulphuric  and  nitric  acid  by  the  signs  SO3  and  NO5,  all  the  neutral 
sulphates  and  nitrates  of  protoxides  are  indicated  by  MO-j-SO3  and 
MO-j-NO5.  There  is,  therefore,  in  the  neutral  protosalts  of  each  fa-  Remarka- 
mily,  a constant  ratio  in  the  oxygen  of  the  base  and  acid,  resulting  blelaw. 
from  the  composition  of  each  acid,  that  ratio  for  sulphates  being  as 

1 to  3,  and  for  nitrates  as  1 to  5.  If  the  metal  M of  a neutral  sul- 
phate pass  into  a higher  grade  of  oxidation,  becoming  a binoxide 
MO2,  then  will  that  binoxide  be  disposed  to  unite  with  two  eq.  of 
acid,  and  form  a bisalt,  MQ2-|-2S03,  in  which  the  oxygen  of  the 
base  and  acid  is  still  as  1 to  3 ; and  if  the  metal  yield  a sesquioxide, 

M203,  then,  if  sufficient  acid  be  supplied,  the  resulting  salt  will  con- 
sist of  M203-(-3S03,  the  ratio  of  1 to  3 being  preserved.* 

Sulphates. 

1319.  The  acid  of  the  sulphates  is  readily  detected  by  chloride  of  Sulphates 
barium  (551).  An  insoluble  sulphate  may  be  detected  by  mixing  it,  detec  ted 
in  fine  powder,  with  three  times  its  weight  of  carbonate  of  potassa 

or  soda,  and  exposing  the  mixture  to  a red  heat  for  half  an  hour,  in 
a platinum  crucible.  Double  decomposition  ensues  ; and  on  digest- 
ing the  residue  in  water,  filtering  the  solution,  neutralizing  the  free 
alkali  by  pure  hydrochloric,  nitric,  or  acetic  acid,  and  adding  chlo- 
ride of  barium,  the  insoluble  sulphate  of  that  base  is  precipitated. 

1320.  Many  sulphates  exist  in  nature,  and  those  of  lime  and  ba-  Natural, 
ryta  are  the  most  abundant.  They  may  all  be  formed  by  the  action  Arljficiaj 
of  sulphuric  acid  on  the  metals,  their  oxides  or  their  carbonates,  or 

by  double  decomposition.  They  vary  in  solubility  in  water  ; most  Solubility, 
of  them  are  decomposed  by  a white  heat  with  the  escape  of  one  part 
of  the  sulphuric  acid,  while  the  other  part  is  resolved  into  sulphurous 
acid  and  oxygen.  They  are  decomposed  by  carbonaceous  mat- ^comP°* 
ter  with  the  aid  of  heat,  carbonic  acid  being  formed  and  a sulphuret 
of  the  metal. 

1321.  The  composition  of  neutral  protosulphates  is  expressed  by  Composi- 

the  formula  MQ-f-SQ3;  the  acid  containing  three  times  as  much  j‘a?sul-eU 
— — ; = phates  ex- 

* This  curious  law  relative  to  oxy-salts,  which  is  very  general,  was  first  noticed  by  pressed. 
Gay  Lussac  {Mem.  d'Arcueil , ii.),  and  Berzelius  has  found  it  to  hold  in  earthy  mine  - 
rals, and  employed  it  as  a guide  in  studying  their  composition.  T. 

41 


322 


Salts — Sulphates. 


chap,  v.  oxygen  as  the  base ; and  if  both  were  deprived  of  it  a metallic  pro- 
tosulphuret  would  result,  M-f-S.* 

Sulphate  of  1322.  Sulphate  of  Potassa.  KO+SO3,  47.15  1 eq.  base  + 40.1 
1 eq.  acid  = 87.25  equiv.  The  sal  de  duohus  of  the  old  chemists, 
potasscB  sulphas  of  the  Pharmacop.  This  salt  is  the  result  of  several 
chemical  operations  in  the  arts  ; and  is  procured  abundantly  by  neu- 
tralizing with  carbonate  of  potassa  the  residue  of  the  operation  for 
preparing  nitric  acid  (471). 

1323.  Its  taste  is  saline  and  bitter.  Its  crystals  belong  to  the 
right  prismatic  system  ; they  are  unchanged  by  exposure  to  the  air, 
but  decrepitate  when  heated.  Soluble  in  sixteen  times  their  weight 
of  water  at  60°,  and  five  of  boiling  water. 

1324.  Intensely  heated  with  one  fifth  its  weight  of  powdered  char- 
coal, it  produces  sulphuret  of  potassium. 

About  two  parts  of  sulphate  of  potassa  and  one  of  lampblack  intimately  mixed 
in  fine  powder,  heated  to  redness  in  a coated  phial,  with  great  care  to  exclude 
the  air  during  cooling,  afford  a compound  which  takes  fire  on  exposure  to  the 
air.  It  appears  to  contain  a compound  of  potassium  which  powerfully  attracts 
oxygen,  and  thus  excites  heat  enough  to  inflame  the  charcoal  and  sulphur.  Gay 
Lussac  attributes  the  combustibility  of  common  pyrophorus  to  this  compound. 

1325.  Bisulphate  of  Potassa.  K0-|-2S03,  eq.  127.35 ; with  1 
water  136.35.  This  salt  is  formed  by  adding  S to  a hot  so- 


potassa, 


Properties, 


Effect  of 
heat  and 
carbon, 


Bisulphate 

formed, 


eq 


weight  of  S in  a 


Properties. 


Old  names. 


lution  of  KO-f-SOs,  or  by  boiling  it  with  half  its 
platinum  crucible,  till  none  of  the  acid  escapes  when  the  heat  ap 
proaches  redness.  It  is  obtained  in  crystals  from  a concentrated 
solution  at  high  temperatures,  as  in  the  cold  the  neutral  sulphate  is 
formed.  The  form  is  a right  rhombic  prism,  generally  tabular.  Ac- 
cording to  Graham  they  contain  1 eq.  water  (basic),  the  bisulphate 
being  a double  sulphate  of  water  and  potassa. 

1326.  It  has  a sour  taste,  and  is  more  soluble  than  the  neutral 
sulphate,  requiring  only  twice  its  weight  of  water  at  60°,  and  less 
than  an  equal  weight  at  212°. 

1327.  It  is  formed  in  the  process  for  nitric  acid  (471),  and  is 
called  sal  enixum — formerly  arcanum  duplicatum  and  panacea  Hoi - 
satica.  It  is  used  for  cleaning  coin  and  other  works  in  metal. 

Sulphate  of  132S.  Sulphate  of  Soda — Glauber's  Salt.  NaO-f-SO3,  31.3  1 eq. 

soda.  base  — |—  40. 3 1 eq.  acid  = 71.4  equiv. ; in  crystals  with  10  eq.  water, 
161.4  eq.  This  salt  occurs  in  the  earth  and  in  the  waters  of  certain 
springs.  It  may  be  obtained  by  saturating  sulphuric  acid  with  carbo- 
nate of  soda.  Large  quantities  are  obtained  as  the  residuum  in  the 
processes  for  hydrochloric  acid  and  chlorine  (610,  629). 

Properties.  1329.  Its  crystals  belong  to  the  right  prismatic  system,  containing 
ten  eq.  of  water,  which  is  lost  by  efflorescence  on  exposure  to  the 
air  ; by  heat  they  undergo  the  watery  fusion.  The  taste  is  bitter, 
cooling,  and  saline.  100  parts  of  water  at  32°  dissolve  12  parts  of 
the  crystals;  at  64.5°  48  parts;  at  77°  100  parts;  at  91.5°  322 
parts. 


Clau  of  iul- 


In  accordance  with  the  views  of  Graham  (22),  the  sulphates  may  be  divided  into 


phate*  accord-  three  classes  : 1st,  anhydrous  sulphates  without  the  eq.  of  constitutional  water ; 2d, 
mg  to  Graham,  ^ose  jn  which  it  is  an  essential  part ; 3d,  double  salts,  produced  from  the  second  by 
the  eq.  of  constitutional  water  being  replaced  by  an  eq.  of  a sulphate  of  the  first 
class.  T. 


323 


Sulphate  of  Baryta . 

1330.  Sulphate  of  soda  is  sometimes  decomposed  for  the  purpose  Sect,  i. 
of  obtaining  soda,  by  igniting  it  with  chalk  and  charcoal.* * * §  Its  Uses, 
principal  use  is  in  pharmacy  and  in  the  manufacture  of  glass. 

1331.  Sulphate  of  Lithia.  LO-f-SO3,  14.44  1 eq.  base  -f-  40.1  1 Sulphate  of 
eq.  acid  ==  54.54  eq.  in  crystals  with  9 1 eq.  water.  This  salt  is  kthia, 
very  soluble  in  water,  fuses  by  heat  more  readily  than  the  sulphates 

of  the  other  alkalies,  and  crystallizes  in  flat  prisms  resembling  sul- 
phate of  soda,  but  not  efflorescent.  Taste  saline. 

1332.  Sulphate  of  Oxide  of  Ammonium — Sulphate  of  Ammonia.  Of  ammo- 
H4N0-f-S03,  26.15  I eq.  base  -f-  40.1  1 eq.  acid  ==  66.25  eq.,  innia» 
crystals  with  9 or  1 eq.  water  = 75.25.  It  is  obtained  by  neutral- 
izing sulphuric  acid  with  carbonate  of  ammonia  ; or  by  decomposing 
hydrochlorate  of  ammonia  by  sulphuric  acid. 

1333.  It  is  important  as  a source  of  the  hydrochlorate  of  ammonia  use. 
which  is  obtained  from  a mixture  of  common  salt  and  sulphate  of 
ammonia  by  sublimation ; by  this  process  sulphate  of  soda  is  also 
formed.!  It  is  contained  in  the  soot  from  coal. 

1334.  It  crystallizes  in  long  flattened  six  sided  prisms  ; dissolves  properties, 
in  two  parts  of  water  at  60°,  and  in  an  equal  weight  of  boiliqg  water. 

In  a warm  dry  air  it  effloresces,  losing  1 eq.  of  water.  Sharply 
heated  it  fuses  and  is  decomposed,  yielding  nitrogen  gas,  water,  and 
sulphate  of  oxide  of  ammonium. 

1335.  Native  Sulphate  of  Ammonia  is  sometimes  found  in  volcanic  Native, 
countries ; it  has  been  procured  from  fissures  in  the  earth  near  cer- 
tain small  lakes  in  Tuscany,  and  is  known  by  the  name  of  Mascag- 
nine.t 

1336.  Sulphate  of  Baryta — heavy  spar.  BaO-j-SO3,  76.7  1 eq.  Sulphate  of 
base  -f-  40.1  1 eq.  acid  = 116.8  eq.  This  is  an  abundant  natural  Bai7ta- 
product,  insoluble  in  hot  and  cold  water,  and  precipitated  when  sul- 
phuric acid  or  any  soluble  sulphate  is  added  to  any  soluble  salt  of 

baryta  (551).  So  extremely  delicate  is  baryta  as  a test  of  sulphuric 
acid,  that  it  shows  the  presence  of  1 part  of  sulphate  of  soda  in  JJ®  as  a 
400,000  of  water.§ 

1337.  Heavy  spar  occurs  associated  with  metallic  ores,  especially  Occurs  in 
those  of  lead,  massive  and  crystallized.  The  form  of  the  crystals  is  naure' 
variable,  being  sometimes  prismatic  and  sometimes  tabular,  deducible 

from  a right  rhombic  prism.  Its  density  is  about  4.4.  It  is  easily 
formed  by  double  decomposition. 

1338.  When  native  sulphate  of  baryta  is  heated  it  decrepitates,  Bologna 
and,  at  a high  temperature,  fuses  into  an  opaque  white  enamel;  it  P^ospho- 
was  employed  in  the  manufacture  of  jasper  ware , by  Wedgwood. 

When  heated  to  redness,  it  acquires  the  property  of  phosphores- 
cence. This  was  first  ascertained  by  Vincenzo  Cascariolo,  of 
Bologna,  whence  the  term  Bologna  phosphorus  is  applied  to  it. II 


*For  a full  account  of  the  processes  for  decomposing  this  salt  see  Aiken’s  Did.  art. 
Mur.  Soda,  and  Brande’s  Manual,  i.  426. 

t In  the  arts  it  is  obtained  by  treating  sulphate  of  lime  with  the  carbonate  of  ammo- 
nia procured  from  animal  matter  by  distillation. 

t From  the  name  of  its-discoverer. 

§ Sulphate  of  baryta  is  sometimes  very  obstinate  in  subsiding  from  water,  and  will 
not  only  long  remain  suspended,  but  even  pass  through  filtering  paper  5 heat  and  a 
little  excess  of  acid  generally  facilitate  its  deposition.  B. 

||  To  prepare  this  substance  the  native  sulphate,  powdered  after  being  ignited,  is  to 


324 


Salts — Sulphates . 

ChaP  v-  This  kind  of  phosphorus,  after  being  exposed  for  a few  minutes  to 
the  sun’s  rays,  shines  in  the  dark  sufficiently  to  render  visible  the 
dial  of  a watch.  This  property  is  lost  by  repeated  use,  in  conse- 
quence of  the  oxygenation  of  the  sulphur  ; but  it  may  be  restored  by 
a second  calcination.* 

1339.  As  the  native  sulphate  is  a common  and  abundant  com- 
Methods  of  pound,  several  processes  have  been  contrived  for  obtaining  from  it 
obtaining  pUre  baryta, 
pure  baryta  . J 

from  native  This  may  be  effected  by  reducing  the  crystallized  sulphate  to  a fine  powder, 
sulphate.  and  heating  it  red-hot  for  half  an  hour  in  a silver  crucible  with  three  parts  of 
carbonate  of  potassa,  the  fused  mass  is  then  boiled  repeatedly  in  water,  till  it  no 
longer  affords  anything  soluble  in  that  liquid;  the  insoluble  residue,  consisting 
chiefly  of  carbonate  of  baryta,  may  be  digested  in  dilute  nitric  acid,  by  which  ni- 
trate of  baryta  is  formed,  and  which  will  yield  the  pure  earth  by  exposure  to  heat. 
Henry’s  The  following  method  has  been  recommended  by  Henry.  The  sulphate  of 
process.  baryta  is  to  be  finely  powdered,  mixed  with  three  or  four  times  its  weight  of  car- 
bonate of  potassa,  and  boiled  with  a proper  quantity  of  water  for  a considerable 
time,  in  an  iron  kettle,  stirring  it,  and  breaking  down  the  hard  lumps,  into  which 
it  is  apt  to  run,  by  an  iron  pestle.  It  is  then  to  be  washed  with  boiling  water, 
as  long  as  this  acquires  any  taste.  On  the  addition  of  dilute  hydrochloric  acid,  a 
violent  effervescence  will  ensue,  and  a considerable  portion  of  the  earth,  probably 
along  with  some  metals,  will  be  dissolved.  To  the  saturated  solution,  add  solu- 
tion of  pure  baryta  in  water,  as  long  as  it  disturbs  the  transparency  of  the  liquor. 
This  will  throw  down  any  metals  that  may  be  present;  and  the  excess  of  baryta 
may  afterwards  be  precipitated  in  the  state  of  a carbonate  by  a stream  of  carbonic 
acid.  Decompose  the  hydrochloric  solution  by  any  alkaline  carbonate  ; let  the 
precipitated  earth  be  well  washed  with  distilled  water  ; and  if  the  pure  baryta  is 
to  be  obtained  from  it,  let  it  be  treated  as  directed  page  238. 

Another.  Another  method  consists  in  exposing  to  a red  heat,  in  an  earthen  crucible,  a 
mixture  of  six  parts  of  finely  powdered  sulphate  of  baryta,  with  one  of  powdered 
charcoal,  for  half  an  hour.  This  converts  the  sulphate  into  sulphuret  which  is 
to  be  dissolved  in  hot  water,  the  solution  filtered  and  mixed  with  solution  of  car- 
bonate of  soda  as  long  as  it  occasions  a precipitate,  which  when  washed  and 
dried,  is  carbonate  of  baryta.  Or,  by  adding  hydrochloric  acid  to  the  liquid  sul- 
phuret, sulphur  is  thrown  down,  hydrosulphuric  acid  gas  evolved,  and  hydro 
chlorate  of  baryta  formed,  which  maybe  filtered  off,  and  if  required,  decomposed 
by  carbonate  of  potassa.  Or  the  sulphuret,  as  it  comes  out  or  the  crucible,  may 
be  thrown  into  dilute  nitric  acid,  by  which  hydrosulphuric  acid  gas  is  evolved, 
and  a nitrate  of  baryta  formed,  which  may  be  separated  from  the  remaining  im- 
purities by  copious  washings  with  hot  water. 

strontfa6  1340.  Sulphate  of  Strontia.  SrO+SO3,  51.8  l eq.  base  -f-  40.1 
1 eq.  acid  = 91.9equiv.  This  salt  occurs  native.  It  is  nearly  in- 
soluble, 1 part  requiring  for  solution  4000  parts  of  cold,  and  3840  of 
hot  water.  Heated  with  charcoal,  its  acid  is  decomposed  and  sul- 
phuret of  strontium  is  formed,  which  affords  nitrate  of  strontia  by 
the  action  of  nitric  acid.  This  process,  equally  practicable  upon  sul- 
phate of  baryta  (884),  is  adopted  to  obtain  strontia. 

Native.  1341.  Native  Sulphate  of  Strontia  is  sometimes  of  a blue  tint,  and 
has  hence  been  called  celestine.  Sometimes  it  is  colourless  and 
transparent.  It  occurs  of  great  beauty  in  Sicily  associated  with  sul- 


be  formed  into  a paste  with  mucilage  of  gum  arabic,  and  divided  into  cylinders  or 
pieces  of  one  fourth  of  an  inch  in  thickness.  These,  after  being  dried  in  a moderate 
heat,  are  to  be  exposed  to  the  temperature  of  a wind  furnace,  placed  in  the  midst  of  the 
charcoal.  When  the  fuel  is  half  consumed,  it  must  be  replenished,  and  suffered  to 
burn  out.  The  pieces  will  be  found,  retaining  their  original  shapes,  among  the  ashes, 
from  which  they  may  be  separated  by  the  blast  of  a pair  of  bellows.  They  must  be 
preserved  in  a well-stopped  phial.  H.  1.  584. 

* The  artificial  sulphate  of  baryta  is  used  as  a pigment,  under  the  name  of  perma- 
nent white.  It  is  very  useful  for  marking  phials  and  jars  in  the  laboratory. 


325 


Sulphate  of  Magnesia. 

phur,  in  anhydrous  prismatic  crystals.  Magnificent  crystals  have  Sect,  i. 
been  met  with  on  Strontian  Island  in  Lake  Erie.* 

1342.  Sulphate  of  Lime.  CaO-j-SO3,  28.5  1 eq.  base  -f-  40-1  Sulphate  of 
1 eq.  acid  = 68.6  eq. ; as  gypsum  with  18  or  2 eq.  of  water  = 86.6.  iime> 

This  salt  is  easily  formed  by  mixing  in  solution  a salt  of  lime  with 

any  soluble  sulphate  (61,  exp.  2).  It  occurs  abundantly  as  a natural 
production.  The  mineral  called  anhydrite  is  anhydrous  sulphate  of  Anhydrite, 
lime,  and  all  the  varieties  of  gypsum  are  composed  of  the  same  salt  Gypsum, 
united  with  water.  The  pure  crystallized  specimens  are  called  sele- 
nite, and  the  white  compact  variety  is  known  as  alabaster.  Alabaster, 

1343.  The  crystals  of  anhydrite  belong  to  the  right  prismatic  sys- Crystalline 
tern,  and  are  isomorphous  with  the  sulphates  of  baryta  and  strontia,  f°rmsi 
while  the  forms  of  gypsum  are  oblique  prismatic.  They  contain  2 

eq.  water,  one  only  of  which  is  considered  by  Graham  to  be  water  of 
crystallization,  the  other  being  constitutional.  The  former  is  readily 
lost  by  exposing  pounded  gypsum  to  a temperature  of  212°  in  vacuo , 
and  the  whole  water  is  expelled  by  a temperature  below  300°.  Thus 
dried,  it  constitutes  the  well  known  plaster  of  Paris,  which,  when  mixed  piaster  of 
with  a proper  proportion  of  water,  rapidly  becomes  dry  and  solid,  Paris, 
owing  to  the  reproduction  of  gypsum.f 

1344.  Nearly  all  spring  and  river  waters  contain  this  salt,  and  in  Contained 
those  waters  which  are  termed  hard  it  is  abundant.  It  gives  them  a 
slightly  nauseous  taste. 

Pour  a quantity  of  hard  water  into  two  glasses,  solution  of  baryta  dropped  into  Exp. 
one  will  detect  the  sulphuric  acid,  and  a solution  of  oxalic  acid  dropped  into  the 
other,  will  detect  the  lime. 

1345.  Sulphate  of  lime  has  hardly  any  taste.  It  is  more  soluble  Solubility, 
than  sulphate  of  baryta  or  strontia,  requiring  for  solution  about  500 

parts  of  cold,  and  450  of  boiling  water. 

rf  1346.  Sulphate  of  Magnesia — Epsom  Salt.  MgO-}-S03HO,  Epsom 
20.7  1 eq.  base  -f-  40.1  1 eq.  acid  9 aq.  1 eq.  = 69.8 ; in  crys-  salt> 
tals  with  54  6 eq.  water  = 123.8  eq.  This  salt  is  usually  obtained  Bowob- 
from  sea-water,  the  residue  of  which,  after  the  separation  of  common  tained. 
salt,  is  known  by  the  name  of  bittern,  and  contains  sulphate  and  hy- 
drochlorate of  magnesia ; the  latter  is  decomposed  by  sulphuric  acid  ; 
a portion  of  the  hydrochlorate  often  remains  in  the  sulphate  and  renders 
it  deliquescent : it  is  also  occasionally  obtained  from  saline  springs  ; 
and  sometimes  by  the  action  of  sulphuric  acid  on  magnesian  lime- 
stone. It  was  procured  from  the  springs  of  Epsom,  in  England, 
and  hence  called  Epsom  salt.  It  has  been  found  native,  constituting 
the  bitter  salt  and  hair  salt  of  mineralogists:  it  not  unfrequently  oc- 
curs as  a fine  capillary  incrustation  upon  the  damp  walls  of  cellars 
and  new  buildings. I 


* Discovered  by  Delafield,  see  Amer.  Jour.  iv.  279. 

tit  is  remarkable  that  gypsum  which  has  lost  only  1 eq.  water,  as  well  as  that 
which  is  dried  by  a heat  exceeding  270°  will  not  act  in  a similar  manner.  In  the  lat- 
ter case  the  powder  is  a perfect  anhydrite.  (Phil.  Mag.  vi.  417.)  Raw  gypsum,  ac- 
cording to  Ernmet,  finely  pulverized,  is  capable  of  undergoing  immediate  and  perfect 
solidification  when  mixed  with  certain  solutions  of  potassa.  See  Auier.  Jour,  xxiii. 
209. 

tThe  sulphate  of  magnesia  of  commerce  is  occasionally  adulterated  with  small 
crystals  of  sulphate  of  soda  5 the  fraud  is  detected  by  the  inferior  weight  of  the  preci- 


326 


Salts — Sulphates . 

ChaP-  v-  1347.  Sulphate  of  magnesia  may  be  made  by  neutralizing  dilute 
Taste  and  sulphuric  acid  with  carbonate  of  magnesia.  It  has  a saline,  bitter, 
formtalline  a.  nauseous  taste>  and  crystallizes  in  small  quadrangular  prisms, 
which  effloresce  slightly  in  a dry  air.  It  is  obtained  also  in  larger 
crystals,  the  principal  form  of  which  is  a right  rhombic  prism. 
Solubility.  1348.  The  crystals  are  soluble  in  an  equal  weight  of  water  at  60°, 
and  in  three  fourths  their  weight  of  boiling  water.  They  undergo 
the  watery  fusion,  and  the  anhydrous  salt  is  deprived  of  a portion  of 
its  acid  at  a white  heat.  Dried  at  212°  it  retains  2 eq.  of  water,  but 
one  of  these  is  expelled  at  270°,  while  the  other  is  retained  till  the 
temperature  rises  to  460°. * 

of  alumina,  1349.  Sulphate  of  Alumina.  A1203+S03,  51.4  1 eq.  base  -f- 
’40.1  1 eq.  acid  = 91.5;  in  crystals  with  81  9 eq.  water  = 172.5. 

Ter  sulphate.  A1203+3S0*,  51.4  acid  -f  120.3  3 eq.  base  = 
171.7  eq. ; in  crystals  with  162  18  eq.  water  = 333.7  eq. 

Tersul-  The  tersulphate  is  prepared  by  saturating  dilute  sulphuric  acid 
phate.  with  hydrated  alumina,  and  evaporating.  It  crystallizes  in  thin  flex- 
ible plates  of  a pearly  lustre,  containing  18  eq.  of  water  and  soluble 
in  twice  their  weight  of  water. 

Hydrated  1350.  The  hydrated  disulphate  is  known  to  mineralogists  under 
sulphate,  the  name  0f  aluminite. t 

Sulphates  1351.  Sulphate  of  Protoxide  of  Iron.  FeO-f-S03HO,  36  1 eq. 
of  iron,  base  -f-  40.1  1 eq.  acid  -f-  9 aq.  1 eq.  =85.  1 ; in  crystals  with  45 
5 eq.  water  = 130.1.  Sulphuric  acid  with  the  protoxide  of  iron 
forms  sulphate  of  the  protoxide , green  vitriol , or  copperas.X  It  is 
Copperas,  prepared  in  large  quantities  for  commercial  purposes,  by  exposing  the 
native  protosulphuret  of  iron  to  air  and  moisture,  the  iron  being  con- 
verted into  an  oxide,  and  the  sulphur  into  sulphuric  acid  by  attract- 
ing oxygen. 

Process.  On  the  small  scale  it  may  be  prepared  by  mixing  C parts  of  iron  with  10  of  S 
and  00  of  water,  evaporating  the  solution  in  a glass  or  earthen  vessel,  after  the 
effervescence  lias  ceased,  and  continuing  the  heat,  till  a rod  dipped  into  it  pre- 
sents appearances  of  crystallization,  when  taken  out  and  held  in  the  air.  The 
solution  may  then  bo  filtered,  and  green  crystals  of  the  sulphate  will  be  formed 
as  it  cools. 

Properties.  1352.  This  salt  has  a strong  styptic  taste.  When  pure  it  does 
not  change  vegetable  blue  colours,  though  generally  stated  to  do  so, 
the  reddening  effect  being  only  produced  when  some  of  the  iron 


pitate,  occasioned  by  adding  carbonate  of  potassa ; 100  parts  of  pure  crystallized  sul- 
phate of  magnesia  furnishing  a precipitate  of  about  40  parts  of  dry  carbonate.  B. 

Much  of  the  sulphate  found  in  the  shops  contains  some  hydrochlorate  ofmagnesia,\vhich 
renders  it  deliquescent,  and  consequently,  it  requires  to  be  preserved  iu  close  and  co- 
vered jars.  It  is  often  adulterated  with  Glauber’s  salt,  which  is  made  to  resemble 
Epsom  salt,  by  stirring  it  briskly,  when  it  is  about  to  crystallize.  It  may  be  detected 
by  precipitating  the  magnesia  by  pure  ammonia,  aiding  by  heat;  filtering  and  evapo- 
rating the  filtered  fluid  to  dryness  by  a heat  sufficient  to  volatilize  the  sulphate  of  am- 
monia ; if  it  contains  Glauber's  salt  the  soda  will  remain  fixed.  Or  it  may  be  detected 
by  no  precipitation  ensuing,  on  adding  carbonate  of  potassa  to  the  solution.  Hydro- 
chlorate of  lime  is  detected  by  the  oxalic  acid.  Thomson’s  Lond.  Disp.  407. 

♦On  the  manufacture  of  this  salt  from  magnesite  see  Amer.  Jour.  iv.  22,  and 
xiv.  10. 

t Sulphate  of  Protox.  Manganese.  MnO+S03HO,  35.7  1 eq.  base  -f  40.1  1 eq. 
acid  + 9 aq-  1 eq.  = 84.8  eq. 

t Native  Green  Vitriol  is  frequently  found  associated  with  iron  pyrites,  being  pro- 
duced by  its  decomposition ; it  occurs  in  some  coal  mines. 


Sulphate  of  Zinc.  327 

passes  into  a higher  state  of  oxidation.  This  is  prevented  by  a few  sect,  i. 
drops  of  sulphuric  acid  in  excess,  and  the  resulting  crystals  have  a 
distinctly  blue  colour.  The  common  green  tint  is  a delicate  test  of 
•the  presence  of  sesquioxide  of  iron.* 

The  crystals  belong  to  the  oblique  prismatic  system,  and  contain  6 Crystalline 
eq.  of  water,  one  of  which  is  retained,  according  to  Graham,  till  the  form- 
temperature  rises  to  535°.  By  operating  carefully  it  may  be  ren- 
dered anhydrous  without  the  loss  of  acid.  It  is  soluble  in  two  parts 
of  cold,  and  in  three  fourths  its  weight  of  boiling  water.  This  salt 
is  employed  in  the  manufacture  of  fuming  sulphuric  acid  (540). 

1353.  When  heated  it  fuses,  and  at  a high  temperature  evolves  a Effect  of 

mixture  of  sulphurous  and  sulphuric  acids,  and  the  oxide  remaining  ileat" 
was  formerly  called  caput  mortuum  vitrioli , or  colcothar.  Colcothar. 

1354.  Tersulphate  of  the  Sesquioxide , Fe203-f-3S03,  80  1 eq.  base  Tersul- 
+ 120.3  3 eq.  acid  = 200.3  eq.,  is  formed  by  mixing  a solution  of  Phale- 

the  protosulphate  with  half  as  much  S as  that  salt  contains,  and 
adding  to  the  mixture  in  a boiling  state  successive  portions  of  nitric 

acid  until  N fumes  cease  to  appear.  The  solution  is  then  evaporated 

to  dryness  to  expel  the  excess  of  N,  and  the  tersulphate  remains 
as  a white  salt. 

1355.  It  dissolves  in  water,  after  being  strongly  heated  ; and  at  a Solubility, 
red  heat  gives  out  all  its  acid,  sesquioxide  of  iron  remaining.  Its  &c. 
solution  in  water  is  yellow.t 

1356.  Sulphate  of  Protoxide  of  Zinc — White  Vitriol,  ZnO  + Sulphate  of 
S03HO,  40.3  1 eq.  base  + 40.1  1 eq.  acid  + 9aq.  1 eq.  = 89.4;  *inc. 

in  crystals  with  54  6 eq.  water  = 143.4.  This  salt  is  the  residue 
of  the  process  for  obtaining  hydrogen  gas,  (378.)t  It  is  also  made 
for  the  purposes  of  commerce,  by  roasting  native  sulphuret  of  zinc. 

1357.  Its  crystalline  form  is  a flattened  four  sided  prism  of  the  Crystalline 
right  prismatic  system,  and  isomorphous  with  Epsom  salt.  The  form,  solu- 
crystals  dissolve  in  2£  parts  of  cold,  and  are  still  more  soluble  in  bi,lty>  &c- 
boiling  water.  Its  taste  is  strongly  styptic.  It  reddens  vegetable 

blue  colours,  though  a neutral  salt. 

1358.  This  salt  is  almost  always  contaminated  with  iron,  and  impUrites 
often  with  copper  and  lead.  Hence  the  yellow  spots  which  are  vis-  removed, 
ible  on  it ; and  hence  also  the  reason  why  its  solution  in  water  lets 

fall  a dirty  brown  sediment.  It  may  be  purified  by  dissolving  it  in 
water,  and  putting  into  the  solution  a quantity  of  zinc  filings ; ta- 
king care  to  agitate  occasionally.  The  zinc  precipitates  the  foreign 
metals  and  takes  their  place.  The  solution  is  then  to  be  filtered 


*BonsdorfFin  Pogg.  Ann.,  xxxi.  81. 

t The  disulphate  of  the  sesquioxide  falls  as  a hydrate  of  an  ochreous  colour,  when  a 
solution  of  the  protosulphate  is  kept  in  an  open  vessel. 

t Hydrogen  gas  holding  zinc  in  solution,  may  be  obtained  by  a process  of  Vauque-  Hydmincic 
lin.  A mixture  of  the  ore  of  zinc,  (blende,  or  calamine)  with  charcoal,  is  to  be  put  gas. 
into  a porcelain  tube,  which  is  to  be  placed  horizontally  in  a furnace,  and  when  red- 
hot,  the  vapour  of  water  is  to  be  driven  over  it.  The  gas  produced  is  a mixture  of 
carbonic  acid,  carburetted  hydrogen,  and  a solution  of  zinc  in  hydrogen  gas,  which 
has  been  called  hydrozincic  gas.  The  zinc  is  deposited  on  the  surface  of  the  water, 
over  which  this  gas  is  kept ; but  if  burned  when  recently  prepared,  the  gas  exhibits, 
in  consequence  of  this  impregnation,  a distinctly  blue  flame. 


328 


Chap.  V. 


Sulphate  of 
nickel. 


Sulphate  of 
cobalt. 


Sulphate  of 
copper. 


Process. 


Disulphate, 


Sulphate  of 
protox. 
cop.  and 
ammonia. 


Salts — Sulphates. 

and  the  sulphate  of  zinc  may  be  obtained  from  it  in  crystals  by 
proper  evaporation.* 

1359.  In  the  dose  of  a scruple  or  a drachm,  sulphate  of  zinc  is  one 
of  the  most  immediate  emetics  we  possess  ; and  it  is  to  be  inferred, 
that  if  larger  doses  are  rejected,  as  is  the  fact,  with  equal  rapidity, 
they  will  in  general  cause  no  more  harm  than  the  medicinal  dose.  In 
some  instances,  however,  persons  have  suffered  severely  from  over- 
doses of  this  salt,  and  a few  have  even  perished.  It  has  also  been 
said  to  have  proved  fatal  when  applied  externally. t 

1360.  Sulphate  of  Protoxide  of  Nickel , NiO-f-SOsHO,  37.5  base 
1 eq.  -f-  40.1  acid  1 eq.  + 9aq.  = 86.6,  like  most  of  the  salts  of 
nickel  this  of  a green  colour,  and  crystallizes  from  its  solution  in 
pure  water  in  right  rhombic  prisms,  similar  to  the  sulphates  of  zinc 
and  magnesia.  If  an  excess  of  acid  is  present  the  crystals  are 
square  prisms,  containing  less  water  and  more  acid  than  the  prece- 
ding.t  Soluble  in  about  three  times  its  weight  of  water  at  60°. 

1361.  Sulphate  of  Protoxide  of  Cobalt , CoO-{-S03HO,  37.5  1 
eq.  base  -f-  40.1  1 eq.  acid  — |—  9 aq.  1 eq.  =86.6,  is  obtained  by  di- 
gesting protoxide  of  cobalt  in  dilute  S,  evaporation  and  crystalliza- 
tion. The  crystals  are  red,  and  isomorphous  with  Fe0-j-S03H0.§ 

1362.  Sulphates  of  the  Oxides  of  Copper. — Blue  Vitriol , CuO-(- 
S03H0,  39.6  1 eq.  base  -f-  40.1  1 eq.  acid  — 9aq.  1 eq.  = 88.7  eq. 
in  crystals  with  36  4 eq.  water  = 124.7.  The  sulphate  of  the 
black  or  protoxide  of  copper  is  made  by  roasting  the  native  sulphu- 

ret,  or  by  dissolving  the  protoxide  in  dilute  S and  crystallizing  by 
evaporation.  It  forms  crystals  of  a blue  colour,  which  contain  5 eq. 
of  water,  4 of  which  are  lost  at  212°  in  dry  air,  but  the  fifth  is  re- 
tained till  the  temperature  exceeds  430°.  It  is  then  a white  powder, 
combining  readily  with  water  with  development  of  heat.  It  is  iso- 
morphous with  MnO-f-S03HO. 

1363.  In  the  large  way  the  the  copper  is  oxidized  by  igniting  it  in  an  oven  ; 
the  scale  of  oxide  is  then  beaten  off  and  the  copper  is  heated  again  till  the  whole 
is  thus  oxidized ; the  scales  heated  in  the  acid  will  partially  dissolve  without 
decomposing  the  latter.|| 

1364.  When  pure  potassa  is  added  to  a solution  of  this  salt,  in  a 
quantity  insufficient  for  separating  the  whole  of  the  acid,  the  disul- 
phate, of  a pale  bluish  green  colour,  is  thrown  down. 

1365.  By  adding  cautiously,  a solution  of  ammonia  to  the  sul- 
phate, until  the  subsalt  thrown  down  is  nearly  all  dissolved,  sulphate 
of  protoxide  of  copper  and  ammonia  is  generated.  The  solution  is 
a rich  blue  from  which  crystals  are  deposited  by  the  addition  of  al- 
cohol. It  may  be  formed  also  by  triturating  carbonate  of  ammonia 


* Thomson’s  Intrg.  Chem.  ii,  610. 

+ Christison  on  Poisons,  375.  For  method  of  detecting  in  contents  of  the  stomach 
see  ibid,  374. 

t Ann.  Philos,  xxii.  439. 

§ Brooke  in  Ann.  Philos.  NS.  vi.  120.  They  are  insoluble  in  alcohol,  but  dissolve 
in  about  24  parts  of  cold  water. 

||  The  composition  of  these  scales  is  variable,  they  are  often  a pure  protoxide,  and 
when  treated  with  hot  S become  peroxide  of  copper,  which  dissolves  and  finely  di- 
vided metallic  copper  subsides.  Their  texture  is  crystalline  and  they  readily  dissolve 
in  ammonia,  and  give,  in  close  vessels,  a colourless  solution.  ( Hayes.) 


Sulphate  of  Silver. 


329 


with  crystals  of  sulphate  of  copper;  carbonic  acid  is  disengaged  and  Sect,  i. 
the  mass  becomes  moist,  the  water  of  the  blue  vitriol  being  liberated. 

This  is  the  cuprum  ammoniatum  of  the  U.  S.  Phar.  and  contains 

S,  Cu-j-0  and  NH3?  It  loses  NH3  by  exposure  to  the  air. 

1366.  Sulphates  of  the  Oxides  of  Mercury.  Sulphate  of  the  Pro - Sulphates 
toxide  HgO-f-SO3  210  l eq.  base  + 40.1  1 eq.  acid  = 250.1  eq.,  isofMercul7- 
obtained  when  two  parts  of  mercury  are  gently  heated  in  three 

parts  of  strong  S,  so  as  to  cause  effervesence  (530). 

1367.  If  a strong  heat  is  employed  so  as  to  excite  brisk  efferves-  Effect  of 
cence,  and  the  mixture  is  brought  to  dryness,  a bisulphate  of  the  pe- heat- 
roxide  results,  both  being  anhydrous.^ 

This  salt  is  employed  in  making  corrosive  sublimate  (1217).  Turpeth 
When  thrown  into  hot  water,  it  is  decomposed,  and  a yellow  sub-mmera  ' 
salt,  formerly  called  Turpeth  mineral ,t  subsides,  according  to  Phil- 
lips it  consists  of  3 eq.  of  acid  and  4 eq.  of  peroxide. 

1368.  Sulphate  of  Oxide  of  Silver.  AgO-j-SO3,  116  1 eq.  base  Sujphate  of 
— |—  40. 1 1 eq.  acid  = 156.1  eq.  This  salt  is  deposited  when  sul- 
phate of  soda  is  mixed  with  nitrate  of  silver.  It  is  also  formed  by 
boiling  silver  with  its  weight  of  sulphuric  acid. 

1369.  It  is  white  and  easily  fusible,  requiring  about  80  times  its  Properties, 
weight  of  hot  water  for  solution,  and  the  greater  part  is  deposited  in 

small  needles  on  cooling. X ■ 

1370.  A compound  acid,  which  may  be  called  nitro-sulphuric, 

consisting  of  one  part  of  nitre  dissolved  in  about  ten  of  S,  dissolves 
silver  at  a temperature  below  200°,  and  the  solution  admits  of  mode- 
rate dilution  before  sulphate  of  silver  separates  from  it.  This  acid 
scarcely  acts  upon  copper,  lead,  or  iron,  unless  diluted  with  water ; 
it  is,  therefore,  useful  in  separating  the  silver  from  old  plated  arti- 
cles : the  precious  metal  may  afterwards  be  separated  either  in  the 
form  of  chloride,  by  adding  common  salt ; or  by  diluting  the  acid  and 
continuing  the  immersion  of  the  pieces  of  copper  which  have  lost 
their  silvering,  and  which  will  now  dissolve  in  the  diluted  acid  and 
occasion  the  precipitation  of  metallic  silver.^ 

1371.  Sulphate  of  oxide  of  silver  forms  with  ammonia  a double  Action  of 
salt,  which  crystallizes  in  rectangular  prisms,  the  solid  angles  and  ammonia, 
lateral  edges  being  replaced  by  tangent  planes.  It  consists  of  1 eq. 

AgO,  1 acid,  and  2 NH3 ; it  is  formed  by  dissolving  AgO-f-SO3  in  a 
hot  concentrated  solution  of  ammonia,  from  which,  on  cooling,  the 
crystals  are  deposited.  It  is  isomorphous  with  the  double  chromate 
and  seleniate  of  oxide  of  silver  and  ammonia.il 


* Donovan  in  Arm.  Philos,  xiv.  + Hydrarg.  sulphas  flavus  of  the  U.  S.  Pharm. 

JUpon  the  large  scale  small  portions  of  gold  may  be  economically  separated  from  Economical 

. . _ method  of  sepa* 

large  quantities  of  silver,  by  heating  the  finely  granulated  alloy  in  S;  the  gold  remains  rating  gold, 
in  the  form  of  a black  powder,  and  the  sulphate  of  silver  may  be  decomposed  by  the 
action  of  metallic  copper  5 the  silver  is  precipitated  in  a pulverulent  state,  and,  with  a 
little  borax  or  other  vitrifiable  flux,  is  fused,  and  cast  into  ingots  3 the  sulphate  of 
copper  is  easily  obtained  in  the  crystallized  state  by  evaporating  the  residuary  liquor. 

B.  ii.  187.  § Keir  in  Phil.  Trans,  lxxx. 

||  Mitscherlich  in  Ann.  de  Chim.  el  de  Phys.,  xxxviii.  62, 

42 


330 


Chap.  V. 


Glauberite. 


Alum, 
Process  for, 


Properties, 

Crystalline 

form, 


Pyropho- 

TUS, 

Process, 


Hare’s, 


Theory  of 
its  combus 
lion, 


Salts — Double  Sulphates. 

Double  Sulphates. 

1372.  Sulphate  of  Soda  and  Lime.  NaO,  S03-f-CaO,  SO3,  71.4 
1 eq.  sulph.  sod.  6S.6  1 eq.  sulp.  lime  = 140  eq.  This  salt,  de- 
scribed by  mineralogists  under  the  name  of  Glauberite , is  found  in 
the  salt  mines  of  New  Castile.  It  may  be  made  by  fusing  together 
its  constituents  in  the  ratio  of  their  equivalents.* 

1373.  Sulphate  of  Potassa  and  Alumina — Alum.  KO,  S03-|- 
A1203,  3S03,  87.25  1 eq.  sulph.  potassa  -j-  171.7  1 eq.  tersulph.  alu. 
= 258.95  eq. ; do.  with  216  or  24  eq.  water  = 474.95.  Common 
alum  is  prepared  by  roasting  and  lixiviating  certain  clays  containing 
iron  pyrites ; to  the  leys  a proper  quantity  of  sulphate  of  potassa  is 
added,  and  the  salt  is  obtained  by  crystallization.  In  Italy  it  is  made 
from  alum  stone  which  occurs  at  Tolfa  near  Rome.  It  occurs  in 
volcanic  countries,  being  probably  formed  by  the  action  of  sulphu- 
rous acid  vapours  on  felspathic  rocks.t 

1374.  Alum  has  a sweetish  taste.  It  is  soluble  in  five  parts  of 
water  at  60°,  and  a little  more  than  its  own  weight  of  boiling  water. X 

1375.  Alum  crystallizes  readily  in  octohedrons  or  in  segments  of 
octohedrons.  When  the  crystals  are  heated,  they  froth  up,  parting 
with  their  water  and  forming  anhydrous  alum,  alumen  exsiccatum  of 
the  U.  S.  Pharmacop. 

1376.  When  alum  is  ignited  with  charcoal,  a spontaneously  in- 
flammable compound  results,  which  has  long  been  known  under  the 
name  of  Homberg’s  Pyrophorus. 

It  is  made  by  mixing  equal  weights  of  alum  and  brown  sugar,  and  stirring  the 
mass  over  the  fire  in  an  iron  ladle  till  quite  dry.  It  is  then  reduced  to  powder 
and  introduced  into  a phial  coated  with  clay  in  a crucible  filled  with  sand.§  The 
whole  is  heated  to  redness,  and  when  a blue  flame  appears  at  the  neck  of  the 
phial,  allow  it  to  burn  about  five  minutes,  then  remove  it  from  the  fire  ; stop  the 
phial  with  a piece  of  soft  clay,  and  when  cool  substitute  a good  cork,  to  exclude 
the  air. 

Hare  recommends  the  following  method,  which  affords  a pyrophorus  that  rarely 
fails.  Take  3 parts  of  lampblack,  4 of  calcined  alum,  and  8 of  pearlashes  ; 
mix  them  thoroughly,  and  heat  them  in  an  iron  tube  to  a bright  cherry  red  for 
one  hour.  On  removal  from  the  fire  the  tube  should  be  carefully  stopped-  \\  hen 
well  prepared  and  poured  out  upon  a glass  plate,  and  especially  when  breathed 
upon,  the  pyrophorus  kindles  with  a series  of  small  explosions.  This  pyropho- 
rus should  be  removed  from  the  tube  with  great  caution,  as  it  has  been  found  to 
explode  violently  on  the  introduction  of  a rod  for  the  purpose  of  loosening  it.|| 

1377.  From  some  experiments  by  Gay-Lussac,  it  appears  that 
' the  essential  ingredient  of  Homberg‘s  pyrophorus  is  sulphuret  of 


* Sulphate  of  Potassa  and  Magnesia , KO,  SOH-MgO,  SO3,  87.25  1 eq.  sulph.  pot. 
+ 60.8  1 eq.  sulph.  magnes.  = 148.05  eq.,  is  formed  on  mixing  solutions  of  the  two 
salts  ; the  crystals  belong  to  the  oblique  prismatic  system. 

Sulph . Ox.  Ammon,  and  Magnes.  H-iNO,  S03+MgO,  SO3,  66.25  l eq.  sulph.  ox. 
ammon.  + 60.8  1 eq.  sulph.  mag.  = 127.05  eq. ; do.  with  54  or  6 eq-  of  water  = 
181.05- 

+ Large  quantities  are  manufactured  in  the  United  States  from  the  purer  clays,  as 
that  of  Martha’s  Vineyard. 

t The  variable  solubility  of  alum  as  stated  by  different  chemists,  may  have  arisen 
from  the  want  of  care  in  selecting  specimens  for  trial.  Hayes  informs  me  that  we 
have  several  varieties  of  alum  in  commerce,  which  vary  in  "solubility ; he  finds  that 
the  pure  potash  alum  is  not  more  soluble  than  has  been  stated  by  Ure,  (1  in  16  water 
at  60°).  W. 

§ I usually  prefer  a small  cast  iron  bottle,  or  retort.  W. 

||  Silliman  in  Amer.  Jour.  o fSci x.  367 


Alum — Varieties. 


331 


potassium  in  a state  of  minute  division.  The  charcoal  and  alumina  Sect,  i. 
act  only  by  being  mechanically  interposed  between  its  particles;  but 
when  the  mass  once  kindles,  the  charcoal  takes  fire  and  continues 
the  combustion.  He  finds  that  an  excellent  pyrophorus  is  made  by 
mixing  27  parts  of  sulphate  of  potassa  with  15  parts  of  calcined  lamp- 
black, and  heating  the  mixture  to  redness  in  a common  Hessian  cru- 
cible, of  course  excluding  the  air  at  the  same  time.* * * § 

1378.  Alum  is  of  extensive  use  in  the  arts,  more  especially  in  uses, 
dyeing  and  calico-printing,  in  consequence  of  the  attraction  which 
alumina  has  for  colouring  matter. 

1379.  Alum,  having  the  same  form,  composition,  appearance,  and  Other  al- 
taste  as  the  salt  just  described,  maybe  made  with  ammonia,!  the  ums- 
sulphate  of  which  replaces  sulphate  of  potassa.  It  is  met  with  occa- 
sionally as  a natural  product,  and  may  be  prepared  by  evaporating  a 
solution  of  sulphate  of  ammonia  with  tersulphate  of  alumina. 

A soda  alum  may  also  be  prepared,  similar  in  form  and  composi- 
tion to  the  preceding  alums,  except  that  it  contains  twentysix  equi- 
valents of  water.!  This  salt  is  disposed  to  effloresce  in  the  air.§ 

1380.  Iron  Alum.  By  mixing  sulphate  of  potassa  with  tersul-  Iron  alum, 
phate  of  sesquioxide  of  iron,  and  crystallizing  by  spontaneous  evapo- 
ration, crystals  are  obtained  similar  to  common  alum,  in  form,  colour , 

taste,  and  composition.  This  salt  has  often  a pink  tint,  but  is  some- 
times quite  colourless.  A similar  double  salt,  quite  colourless,  may 
be  made  with  ammonia  instead  of  potassa.  In  both  these  alums  the 
alumina  is  simply  replaced  by  an  equivalent  quantity  of  oxide  of 
iron. 

1381.  Chrome  Alums.  The  tersulphate  of  sesquioxide  of  chromi-  Chrome  al- 
um forms  with  the  sulphates  of  potassa  and  ammonia  double  salts 

which  are  exactly  similar  in  form  and  composition  to  the  preceding 
varieties  of  alum.  They  appear  black  by  reflected,  but  ruby-red  by 
transmitted  light. 

1382.  Manganese  Alum.  Mitscherlich  obtained  this  salt  by  mix- Manganese 
ing  a solution  of  tersulphate  of  sesquioxide  of  manganese  with  sul-  alum* 
phate  of  potassa,  and  evaporating  to  the  consistence  of  syrup  by  a 

very  gentle  heat.|| 

1383.  The  salts  to  which  the  term  alum  is  applied,. are  character-  Character- 
ized by  two  common  properties  ; they  all  crystallize  in  the  octohedral  peJtiesof 
system,  and  they  are  all  constituted  as  represented  by  the  formula  alum. 
R0S03+R2033S03-|-24Aq.  ; where  RO  represents  an  eq.  of  po- 

tassa,  or  oxide  of  ammonium,  and  R'O3  any  one  of  the  isomorphous 
sesquioxides  of  aluminium,  iron,  manganese,  and  chromium.  As 
remarked  by  Berzelius,  the  formula  and  crystalline  form  serve  to 
determine  the  genus  alum,  and  the  oxidized  bases  its  species. IT  t.  and 
L.  667. 

* An.  de  Ch.  et  de  Ph.,  xxxvii.  415* 

+ H4NO,  S03+A1203,  3S03,  66.25  1 eq.  sulph.  ox.  ammon.  + 171.7  1 eq.  tersulph. 
alumina  = 237.95  eq.  5 do.  with  216  or  24  eq.  water  = 453.95. 

t Berzelius. 

§ NaO,  S03+A1203  3S03,  71.4  1 eq.  sulph.  soda  + 171-7  1 eq.  tersulph.  alumina  = 

243.1,  eq.  5 do-  with  234  or  26  eq.  water  = 477.1. 

||  KO,  S03+MnO,  SO3,  87.25  1 eq.  sulph.  potassa + 75.8  1 eq.  sulph.  protox.  mang. 

= 163.05  eq. ; do  with  54  or  6 eq.  water  = 217.05. 

IT  For  Sulphates  of  Protoxide  of  Iron  and  Alumina  and  remarks  on  Anhydrous 
Sulphates  with  Ammonia,  see  Turner  and  Liebig’s  Chem.,  667. 


332 


Salts — Nitrates. 


Chap.  V. 
Sulphites.  J 


Effect  of 
heat. 


Nitrates. 


Effect  of 
heat,  &c. 


Oxidize. 


Deflagra- 

tion. 


Sulphites. 

1384.  The  salts  of  sulphurous  acid  have  not  hitherto  been  mi- 
nutely examined.  The  sulphites  of  potassa,  soda,  and  ammonia, 
made  by  neutralizing  those  alkalies  with  sulphurous  acid,  are  solu- 
ble in  water,  but  most  of  the  other  sulphites  are  of  sparing  solubili- 
ty. The  sulphites  of  baryta,  strontia,  and  lime  are  very  insoluble. 

The  stronger  acids  decompose  all  the  sulphites  with  effervescence, 
owing  to  the  escape  of  sulphurous  acid,  which  may  easily  be  recog- 
nised by  its  odour.  Nitric  acid,  by  yielding  oxygen,  converts  the 
sulphites  into  sulphates. 

1385.  When  the  sulphites  of  the  fixed  alkalies  and  alkaline  earths 
are  strongly  heated  in  close  vessels,  a sulphate  is  generated,  and  a 
portion  of  sulphur  sublimed.  In  open  vessels  at  a high  tempera- 
ture they  absorb  oxygen,  and  are  converted  into  sulphates ; and  a 
similar  change  takes  place  even  in  the  cold,  especially  when  they 
are  in  solution. 

The  kyposulphates  and  hyposulphites  are  of  little  practical  impor- 
tance.* 

Nitrates. 

13S6.  The  nitrates  may  be  prepared  by  the  action  of  nitric  acid 
on  metals,  on  the  salifiable  bases  themselves,  or  on  carbonates.  As 
nitric  acid  forms  soluble  salts  with  all  alkaline  bases,  the  acid  of 
the  nitrates  cannot  be  precipitated  by  any  reagent.  They  are  readi- 
ly distinguished  from  other  salts,  however,  by  the  characters  already 
described.  (484.) 

1387.  All  the  nitrates  are  decomposed  without  exception  by  a 
high  temperature;  but  the  changes  which  ensue  are  modified  by  the 
nature  of  the  oxide.  Nitrate  of  oxide  of  palladium  is  decomposed 
at  a moderate  temperature.  Nitrate  of  protoxide  of  lead  requires  a 
red  heat,  by  which  it  is  resolved  into  oxygen  and  nitrous  acid.  In 
some  instances  the  changes  are  more  complicated. 

1388.  As  the  nitrates  are  easily  decomposed  by  heat  alone,  they 
must  necessarily  suffer  decomposition  by  the  united  agency  of  heat  | 
and  combustible  matter.  The  nitrates  on  this  account  are  much  I 
employed  as  oxidizing  agents,  and  frequently  act  with  greater  effica- 
cy even  than  nitro-hydrochloric  acid. 

The  efficiency  of  nitre,  which  is  the  nitrate  usually  employed  for 
the  purpose,  depends  not  only  on  the  affinity  of  the  combustible  for 
oxygen,  but  likewise  on  that  of  the  oxidized  body  for  potassa.  The 
process  for  oxidizing  substances  by  means  of  nitre  is  called  deflagra- 
tion, and  is  generally  performed  by  mixing  the  inflammable  body 
with  an  equal  weight  of  the  nitrate,  and  projecting  the  mixture  in 
small  portions  at  a time  into  a red-hot  crucible. 

All  the  neutral  nitrates  of  the  fixed  alkalies  and  alkaline 
earths,  together  with  most  of  the  neutral  nitrates  of  the  common 
metals,  are  composed  of  one  equivalent  of  nitric  acid,  and  one  equiv- 
alent of  a protoxide.  Consequently,  the  oxygen  of  the  oxide  and 
acid  in  all  such  salts  must  be  in  the  ratio  of  1 to  5,  the  general  for- 
mula being  MO-f-NO5. 

* For  their  characters  see  T.  & L.  Elem.  307,  and  Heeren  in  Ann.  de  Chirn.  et 
Phys,  ad.  30. 


Nitrate  of  Potassa. 


333 


The  only  nitrates  found  native  are  those  of  potassa,  soda,  lime,  Sect,  i. 
and  magnesia. 

1389.  Nitrate  of  Potassa — Nitre , KO+NO5,  47.15  1 eq.  base-f-  Nitrate  of 
54.15  1 eq.  acid  =101.3  eq.  This  salt  is  an  abundant  natural  pro- potassa. 
duct,  and  is  principally  brought  to  this  country  from  the  East  Indies, 
where  it  is  produced  by  lixiviation  of  certain  soils.* * * § 

The  rough  nitre  is  in  broken  crystals,  of  a brown  colour,  and  more 
or  less  deliquescent:  exclusive  of  other  impurities,  it  often  contains 
a very  considerable  proportion  of  common  salt,  which  reacting  upon 
the  nitre,  induces  the  production  of  nitrate  of  soda  and  chloride  of 
potassium. 

1390.  In  Germany  and  France  it  is  artificially  produced  in  what  Artificial 

are  termed  nitre-beds. t Thenard  has  described  the  French  process  production 
at  length.  ofwlre- 

It  consists  in  lixiviating  old  plaster  rubbish, t which  when  rich  in  nitre,  affords 
about  five  per  cent.  Refuse  animal  and  vegetable  matter  which  has  putrefied 
in  contact  with  calcareous  soils  produces  nitrate  of  lime,  which  affords  nitre  by 
mixture  with  subcarbonate  of  potassa.  In  the  same  way  it  is  abundantly  pro- 
duced in  some  parts  of  Spain.  Exudations  containing  saltpetre  are  not  uncom- 
mon upon  new  walls,  where  it  appears  to  arise  from  the  decomposition  of  ani- 
mal matter  contained  in  the  mortar.  It  was  long  ago  shown  by  Glauber,  that  a 
vault  plastered  over  with  a mixture  of  liriie,  wood-ashes,  and  cows’  dung,  soon 
becomes  covered  with  efflorescent  nitre,  and  that  after  some  months,  the  mate- 
rials yield,  on  lixiviation,  a considerable  proportion  of  that  salt. 

1391.  Nitre  crystallizes  in  six-sided  prisms,  it  dissolves  in  7 parts  Properties, 
of  water  at  60°  and  in  its  own  weight  at  212°.  Its  taste  is  cooling 

and  peculiar.  It  contains  no  water  of  crystallization,  but  its  crys- 
tals are  never  quite  free  from  water  lodged  mechanically  within 
them. 

1392.  When  exposed  to  a white  heat,  nitre  is  decomposed  into  Effect  of 
oxygen,  (365)  nitrogen,  and  dry  potassa.  By  distilling  it  in  an  earth- heat- 
en  retort,  or  in  a gun-barrel,  oxygen  gas  may  be  obtained  in 

great  abundance,  one  pound  of  nitre  yielding  about  12,000  cubic 
inches,  of  sufficient  purity  for  common  experiments,  but  not  for  pur- 
poses of  accuracy.  It  fuses  at  a heat  below  redness,  and  congeals 
on  codling  into  cakes  called  sal  prunelle. 

If  the  temperature  of  nitre  be  so  far  increased  as  to  allow  a por- 
tion of  oxygen  to  escape,  the  remaining  salt,  as  Scheele  first  observed, 
remains  neutral,  and  in  this  state  it  has  been  considered  as  forming 
a nitrite  of  potassa. 

1393.  It  is  decomposed  by  charcoal  at  a red  heat,  and  if  excess  Decompo- 

sed by 

of  charcoal  be  used  the  results  are  C,  C,  N and  KO-j-CO.  It  is  charcoal, 
also  decomposed  by  sulphur  with  different  results,  according  to  the 
temperature  and  proportions  employed. 

This  may  be  shown  by  mixing  two  parts  of  powdered  nitre  with  one  of 
powdered  charcoal,  and  setting  fire  to  the  mixture  in  an  iron  vessel  under  a 
chimney. § 


* In  Kentucky  and  other  parts  of  the  U.  S.  the  caverns  in  limestone  afford  abun- 
dant supplies  of  nitrate  of  lime  from  which  nitre  is  obtained.  The  potassa  is  ob- 
tained from  wood  ashes.  In  some  places  1 bushel  of  the  earth  yields  from  3 to  10 
lbs.  of  the  salt.  Amer.  Jour.  1.  321. 

+ TraiU  de  Chim.  Elem.  ii.  511. 

t The  greater  part  of  the  nitre  made  in  France  is  thus  obtained, 

§ The  residuum  is  known  as  white  flux. 


334 


Salts — JVitrutes. 


Chap  v. 
Exp. 


Exp. 


Combus- 
tion with 
phospho- 
rus, &c. 


Fulmina- 
ting pow- 
der. 


Use  of 
nitre  in 
chemistry, 


In  the  arts. 


Composition  of 
gunpowders. 


Mix  powdered  nitre  and  sulphur,  and  throw  the  mixture,  by  a little  at  a time, 
' into  a red-hot  crucible.  The  sulphur  will  unite  with  the  oxygen  of  the  nitric 
acid,  and  form  sulphuric  acid;  which,  combining  with  the  potassa,  will  afford 
sulphate  of  potassa.  The  production  of  the  latter  salt  will  be  proved  by  dissolv- 
ing the  mass  remaining  in  the  crucible,  and  crystallizing,  when  a salt  will  be 
obtained  exhibiting  the  characters  of  the  sulphate. 

Mix  a portion  of  sulphur  with  one  sixth  or  one  eighth  its  weight  of  nitrate  of 
potassa ; put  the  mixture  into  a tin  cup ; and  raise  it,  by  a small  stand,  a few 
inches  above  the  surface  of  water,  contained  in  a flat  shallow  dish.  Set  fire  to 
the  mixture,  and  cover  it  with  a bell-shaped  receiver.  In  this  case,  also,  sulphu- 
ric acid  will  be  formed;  but  it  will  not  combine,  as  before,  with  the  alkali  of  the 
nitre,  which  alkali  is  present  in  sufficient  quantity  to  absorb  only  a part  of  the 
acid  produced.  The  greater  part  of  the  acid  will  be  condensed  on  the  inner  sur- 
face of  the  glass  bell,  and  by  the  water,  which  will  thus  become  intensely  acid. 
The  operation  may  be  repeated  three  or  four  times,  using  the  same  poriion  of 
water.  When  the  water  is  partly  expelled,  by  evaporation  in  a glass  dish,  con- 
centrated sulphuric  acid  remains.  II.  1.  520. 

When  phosphorus  is  thrown  upon  nitre,  and  inflamed,  a vivid 
combustion  ensues,  and  a phosphate  of  potassa  is  formed.  Sulphur 
sprinkled  upon  hot  nitre  burns,  and  produces  a mixture  of  sulphate 
and  sulphite  of  potassa.  This  salt  used  formerly  to  be  employed  in 
medicine,  under  the  name  of  Glaser's  polyckrest  salt.  Most  of  the 
metals,  when  in  filings  or  powder,  detonate  and  burn  when  thrown 
on  red-hot  nitre  ; some  of  the  more  inflammable  metals  produce  in 
this  way  a considerable  explosion. 

1394.  A mixture  of  three  parts  of  nitre,  two  of  dry  subcarbonate 

of  potassa,  and  one  of  sulphur,  forms  fulminating  powder .*  If  a 

little  of  this  compound  be  heated  upon  a metallic  plate,  it  blackens, 
fuses,  and  explodes  with  much  violence,  in  consequence  of  the  rapid 
action  of  the  sulphur  upon  the  nitre. 

1395.  Nitre  is  employed  in  chemistry  as  an  oxidizing  agent,  and 
in  the  formation  of  nitric  acid  (471).  It  is  employed  in  the  East 
Indies  for  the  preparation  of  cooling  mixtures  ; an  ounce  of  nitre 
dissolved  in  five  ounces  of  water  reduces  its  temperature  15°.  It  is 
highly  antiseptic  and  much  used  in  the  preservation  of  animal  sub- 
stances. 

1396.  Its  chief  use  in  the  arts  is  in  making  gunpowder,  which 
consists  of  a very  intimate  mixture  of  nitre,  sulphur,  and  charcoal.t 


♦Or  nitre  2 parts,  neutral  carbonate  of  potassa  2,  sulphur  1,  and  sea-salt  6,  all  in 
fine  powder.  Ferussac’s  Bulletin , 1828. 

+ The  proportions  vary.  For  a description  of  the  manufacture,  &c.,  see  Ure’s  Diet. 
Arts  and  Manuf.  p.  620,  from  which  the  following  table  of  composition  of  different 
gunpowders  is  taken. 


Nitre.  Charcoal. 

Sulphur. 

Royal  Mills,  Waltham  Abbey,  - 

France,  national  establishment, 

French,  for  sportsmen, 

“ “ mining,  - 

U.  S.  of  America, 

Prussia,  ------- 

Russia,  - --  --  --  - 

Austria  (musquet), 

Spam, 

Sweden, 

Switzerland  (a  round  powder),  - 

Chinese, * 

Theoretical  proportions, 

75 

75 

78 

65 

75 

75 

73.75 

72 

76.47 

76 
76 
75 
75 

15 

12.6 

12 

15 

12.5 

13.5 
13.59 
17 

10.78 

15 

14 

14.4 

13.23 

10 

12.5 

10 

20 

12.5 

11.5 
12.63 
16 

12.75 

9 

10 

9.9 

11.79 

335 


Nitrate  of  Baryta. 

1397.  Gunpowder  explodes  at  600°  F.  The  violence  of  the  eX-  Sect.  i. 
plosion  depending  upon  the  sudden  production  of  gaseous  matter  Products  of 
resulting  from  the  action  of  the  combustibles  upon  the  nitre. ^ explosion 

C,  C,  N,  and  S are  the  principal  gaseous  results.  der\UnP°W 

1398.  Gunpowder  maybe  inflamed  by  a violent  blow  ; if  mixed  Inflamed 
with  powdered  glass,  or  any  other  harder  substance,  and  struck  with  bY  fnctlon* * 
a heavy  hammer  upon  an  anvil,  it  almost  always  explodes. 

1399.  Nitrate  of  Soda.  NaO-j-NO5,  31.3  1 eq.  base  -f-  54.15  1 Nitrate  of 
eq.  acid  = 85.45  eq.  This  salt,  the  cubic  nitre  of  old  writers, soda’ 

is  analogous  in  chemical  properties  to  the  preceding.  It  crystallizes 
in  oblique  rhombic  prisms ; but  more  commonly  in  the  form  of  an 
obtuse  rhombohedron.  It  occurs  in  the  soil  of  India,  and  covers 
large  districts  in  Peru. 

1400.  Mixed  with  charcoal  and  sulphur  it  burns,  but  more  slowly 
than  nitre.  It  may  be  advantageously  used  in  the  manufacture  of 

both  S and  N. 

1401.  Nitrate  of  Oxide  of  Ammonium.  H4N0-f-N05,  26.15,  Of  ammo- 
base  -J-  54.15  acid  — 80.3  eq.  This  salt  may  be  procured  by  the  nia’ 
direct  union  of  ammonia  with  nitric  acid;  or  more  easily  by  satu- 
rating dilute  N with  carbonate  of  ammonia,  and  evaporating  the  so- 
lution. The  state  of  the  salt  varies  with  the  temperature  at  which 

the  evaporation  is  carried  on.t  At  100°  it  is  obtained  in  prismatic 
crystals  isomorphous  with  nitre  ; at  212°  it  is  fibrous,  at  300°  it 
forms  a compact  mass  on  cooling.  The  fibrous  and  compact  varie-. 
ties  still  contain  water,  the  former  8.2  per  cent.,  and  the  latter  5.7. 

All  the  varieties  deliquesce  and  are  very  soluble. 

1402.  It  is  the  source  of  N (446).  When  heated  to  600  it  ex-  Use. 
plodes,$  being  resolved  into  water,  N,  N,  and  N.  The  fibrous  vari- 
ety yields  the  largest  quantity  of  N ; from  one  pound  of  the  salt 
nearly  three  cubic  feet  of  gas  may  be  obtained. 

1403.  Nitrate  of  Baryta.  BaO-f-NO5,  76.7  1 eq.  base  -J-  54. 15  Nitrate  of 
1 eq.  acid  = 130.85  eq.  It  maybe  obtained  by  dissolving  car- barYta- 

bonate  of  baryta  in  N,  evaporating  to  dryness,  redissolving  and 
crystallizing  ; it  forms  transparent  anhydrous  octohedrons,  and  is  apt 


The  portfire  used  for  firing  artillery  is  mane  of  three  parts  of  nitre,  two  of  sulphur, 
and  one  of  gunpowder,  well  mixed  and  rammed  m cases. 

Signal  lights  are  generally  composed  ot  mire  and  sulphur,  with  a small  quantity  of  nalUohu 
some  metallic  sulphuret,  as  that  of  arsenic  or  antimony.  Mix  600  grains  of  nitre  with  i,sna  18 
200  of  sulphur  and  100  of  the  yellow  sulphuret  of  arsenic  ; put  the  mixture  into  a cone 
of  paper,  and  touch  it  (out  of  doors  or  under  a large  chimney),  with  a red-hot  iron  ; it 
will  hum  rapidly  with  a brilliant  white  light. 

Mix  1 0ft  or  20Q  grains  of  sulphuret  of  antimony  with  the  same  proportions  of  nitre 
and  sulphur ; it  will  burn  with  a vivid  light  having  a bluish  tinge.  For  other  compo- 
sitions used  in  pyrotechny,  see  Ure’s  Did.  and  Gray’s  Oper.  Chem.  496. 

* The  volume  of  gases  produced  from  gunpowder  is  at  60°,  250  times,  and  at  the  mo- 
ment of  discharge  1000  times  greater  than  that  of  the  powder;*  as  each  additional  of  ex' 
vol.  of  gas  exerts  a force  equal  to  that  of  the  atmosphere,  1000X  15=15.000  lbs.  on  a pansi0n’ 
square  inch,  which -will  project  a bullet  with  a force  of  2000  feet  in  a second.  (Murray.) 

Ure  estimates  it  theoretically  at  upwards  of  2000  times  Did.  627. 

+ Davy’s  Researches. 

* Hence  it  was  formerly  called  nitrum  Jlammans . 

* Robbins’  Essay  on  Gunnery , and  Nicholson’s  Jour.  iv.  258. 


336 


Salts — Nitrates. 


Chap.  V. 


Nitrate  of 
strontia. 


Nitrate  of 
lime 


Nitrate  of 
copper. 

Effect  of 
heat. 

Exp. 


Green  fire. 


Red  fire. 


to  decrepitate  by  heat  unless  previously  reduced  to  powder.  It  re- 
quires 12  parts  of  water  at  60°  and  3 or  4 of  boiling  water  for  solu- 
tion. It  is  used  as  a reagent,* * * §  and  for  preparing  pure  baryta. t 

1404.  Nitrate  of  Strontia.  SrO-f-NO5,  51.8  1 eq.  base  -f-  54.15 
l eq.  acid  = 105.95  eq. ; in  prisms  with  45  or  5 eq.  water  = 
150.95  eq.  This  salt  may  be  made  from  the  sulphate  or  carbonate 
of  strontia  in  the  same  manner  as  the  preceding.  It  crystallizes  in 
anhydrous  octohedons  ; it  sometimes  contains  30  per  cent,  of  water 
of  crystallization  and  then  assumes  the  form  of  the  oblique  prismatic 
system.! 

1405.  Nitrate  of  Lime.  CaO-f-NO5,  28.5  1 eq.  base  -|-  54.15  l 
eq.  acid  = 82.65  eq.  Nitrate  of  lime  is  a deliquescent  salt,  soluble 
in  4 parts  of  water  at  60°.  it  is  found  in  old  plaster  and  mortar, 
from  the  washings  of  which,  nitre  is  procured  by  the  addition  of 
carbonate  of  potassa  (1381).  When  moderately  heated  it  fuses,  and 
on  cooling  concretes  into  a semitransparent  mass  known  as  Bald - 
loin's  phosphorus 

1406.  Nitrate  of  Protoxide  of  Copper , CuO+NO5  39.6  1 eq. 

base  4-  54.15  acid  = 93.75  eq.,  is  obtained  by  the  action  of  N on 
copper  (455).  It  crystallizes  in  prisms  of  a deep  blue  colour,  soluble 
in  water  and  alcohol,  and  deliquescent.  By  exposure  to  a heat  of 
400°,  a green  insoluble  subsalt  is  obtained.il 

1407.  When  this  salt  is  heated  to  redness,  it  yields  pure  oxide  of 
copper.  It  is  sometimes  used  as  an  escharotic.  It  is  decomposed  by 
tin  with  the  evolution  of  heat  and  N. 

Spread  a drachm  or  two  of  the  salt  in  coarse  powder  on  a piece  of  tin-foil,  se- 
veral inches  square,  moisten  it  with  a few  drops  of  water,  fold  it  up  quickly, 
and  lay  it  upon  a plate  ; much  heat  will  be  evolved  and  the  metal  often  takes 
fire. IT 

1408.  Nitrates  of  the  Oxides  of  Mercury — Nitrate  of  the  Pro- 
toxide,, HgO+NO5,  210  base  1 eq.  + 54.15  1 eq.  acid  = 264.15; 
in  crystals  with  18  or  2 eq.  water  = 282.15  eq. 


* If  a moderately  strong  solution  of  this  salt  he  added  to  N,  a precipitation  of  nitrate 
of  baryta  lakes  place,  in  consequence  of  the  insolubility  of  the  nitrate  in  the  acid  ; 

hence  in  using  nitrate  of  baryta  as  a test  of  S,  the  latter  should  be  considerably  diluted 
previous  to  its  application.  B. 

t This  salt  is  employed  in  pyrotechny  to  impart  a green  colour  to  flame.  The  green 
fire  is  composed  of  13*parts  sulphur,  77  nitrate  of  baryta,  chlorate  of  potassa  5,  arsenic 
2,  and  charcoal  3.  The  nitrate  should  be  well  dried,  powdered,  and  mixed  with  the 
other  ingredients,  the  powdered  chlorate  being  added  afterwards,  and  mixed,  with 
caution, on  a sheet  of  paper,  and  with  an  ivory  or  wooden  spatula. 

tThis  salt  is  used  in  the  red,  fire  employed  at  the  theatres,  which  consists  of  40 
parts  dry  nitrate  of  strontia,  13  sulphur,  5 chlorate  of  potassa.  and  4 sulphuret  of  anti- 
mony. The  chlorate  and  sulphuret  should  be  separately  powdered,  and  mixed  on  pa- 
per with  the  other  ingredients  j a very  small  quantity  of  powdered  charcoal  may  also 
be  added. 

§ Birch’s  Hist  of  Roy.  Soc.,  iii.  323. 

H The  neutral  salt  contains  3 eq.  of  constitutional  water,  and  may  be  represented  by 
the  formula  CuO  NO’  3 HO ; the  subsalt  is  supposed  to  be  similarly  constituted,  being 
a nitrate  of  water  with  3 eq.  of  constitutional  oxide  of  copper,  and  may  be  represented 
by  the  formula  HO  NOo  3CuO.  T.  673. 

IT  Nitrate  of  Protoxide  of  Lead  PbO+NO5,  111.6  1 eq.  base  -f  54.15  1 eq.  acid 
= 165.75  eq.,  is  formed  by  digesting  litharge  in  dilute  N. 


Nitrate  of  Silver. 


337 


Sect.  T. 


Protoni- 
trate of 
mercury. 


Pernitrate 
of  mercury. 


Nitrate  of  the  Peroxide,  Hg02-)-N05,  218  1 eq.  base -f- 54.15 
acid  = 272.15. 

Dinitrate , 2HgQ2-|-N05,  436  2 eq.  base  -f-  54.15  acid  — 490.15 
eq. 

The  protonitrate  is  obtained  by  digesting  mercury  in  N,  diluted 
with  3 or  4 parts  of  water,  until  the  acid  is  saturated,  and  then  al- 
lowing the  solution  to  evaporate  spontaneously  in  an  open  vessel. 

The  solution  always  contains,  at  first,  some  nitrate  of  the  peroxide  ; 
but  if  metallic  mercury  is  left  in  the  liquid,  a pure  protonitrale  is 
gradually  deposited.* * * § 

1409.  When  mercury  is  heated  in  an  excess  of  strong  N,  it  is 
dissolved  with  brisk  effervescence,  owing  to  the  escape  of  N,  and 
transparent  prismatic  crystals  of  the  pernitrate  are  deposited  as  the 
solution  cools.  When  put  into  hot  water  it  is  resolved  into  a solu- 
ble salt  the  composition  of  which  is  unknown,  and  into  a yellow 
dinitrate  of  the  peroxide  ;t  this  is  the  nitrous  turpeth  of  old  wrh 
ters.l 

1410.  Nitrate  of  Oxide  of  Silver , AgO-f-NO5,  116  1 eq.  base 
-j-  54.15  1 eq.  acid  — 170.15.  Nitric  acid  diluted  with  three  parts 
of  water,  readily  dissolves  silver,  with  the  disengagement  of  N.  If 
the  acid  contain  the  least  portion  of  hydrochloric,  the  solution  will 
be  turbid,  and  deposit  a white  powder  ; and  if  the  silver  contain 
copper,  it  will  have  a permanent  greenish  hue  ; or  if  gold,  that  met- 
al  will  remain  undissolved  in  the  form  of  a black  powderA 

The  solution  should  be  perfectly  clear  and  colourless ; it  is  caus- 
tic, and  tinges  animal  substances  of  a deep  yellow,  which,  by  ex- 
posure to  light,  becomes  a deep  purple,  or  black  stain,  and  is  indeli- 
ble, or  peels  off  with  the  cuticle : it  consists  of  reduced  silver. 

1411.  It  may  be  obtained  in  transparent  tabular  crystals,  by  evap-  Crystals, 
oration.  These  crystals,  which  are  anhydrous,  undergo  the  igneous 
fusion  at  426°,  and  yield  a crystalline  mass  on  cooling  ; but  at  600° 

or  700°,  complete  decomposition  ensues,  the  acid  being  resolved  into 

O and  N,  and  metallic  silver  is  left. 

1412.  When  heated  in  a silver  crucible  it  fuses,  and  if  cast  into  Lunar 
small  cylinders,  forms  the  lapis  infernalis , or  lunar  caustic  of causUc- 


Nitrate  of 
silver. 


* According  to  Mitscherlich,  it  is  a sub-salt,  in  which  the  protoxide  and  acid  are  in 
the  ratio  of  20S  to  36.  The  neutral  protonitrale  is  said  to  be  obtained  in  crystals,  by 

dissolving  the  former  salt  in  pure  water,  acidulated  with  N,  and  evaporating  sponta- 
neously without  the  contact  of  metallic  mercury  or  uncombined  oxide.  Pog.  Ann. 
ix.  387. 

t Ann.  de  Ch.  et  Phys.  xix. 

t In  preparing  these  salts  for  different  purposes,  great  attention  should  be  paid  to 
the  strength  of  the  acid  employed,  the  temperature,  and  the  relative  proportions,  as 
all  these  circumstances  have  an  important  influence  upon  the  oxidation  of  the  mercu- 
ry and  the  nature  of  the  resulting  salt.  R. 

§ A very  useful  solvent  of  silver  is  formed  by  dissolving  one  part  of  nitre  in  about  Nitr0-suiphim 
eight  or  ten  parts  by  weight  of  concentrated  sulphuric  acid*  This  compound  (which  acid, 
may  be  called  nitro-sulphuric  acid)  when  heated  to  between  100°  and  200°  F.  dis- 
solves one  fifth  or  one  sixth  its  weight  of  silver,  with  an  extrication  of  nitrous  gas  ; 
and  leaves  untouched,  any  copper,  gold,  lead,  or  iron,  with  which  the  silver  may  be 
combined.  Hence  it  is  a most  useful  agent  in  extracting  silver  from  old  plated 
goods.  The  silver  may  be  recovered  from  the  solution  by  adding  common  salt,  and 
the  chloride  of  silver  formed  may  be  decomposed  by  carbonate  of  soda. 

43 


338 


Salts — Nitrates. 


Chap  V. 


Solubility. 


Effect  of 
light. 


Action  of 

sulphur, 

&c. 

Exp. 


Exp. 


Exp. 


Arbor  Di- 
anas. 

Indelible 

ink. 


pharmacy  ; the  argenti  nitras  of  the  Pharmacop.  In  forming  this 
preparation,  care  should  be  taken  not  to  overheat  the  salt,  and  the 
moulds  should  be  warmed.  When  pure  it  is  white  and  transparent, 
and  does  not  deliquesce  on  exposure  to  the  air  ; but  common  lunar 
caustic  is  often  dark  and  opaque,  and  dissolves  imperfectly  in  water, 
owing  to  some  of  the  nitrate  being  decomposed  during  its  prepara- 
tion. It  is  impure,  also,  containing  nitrate  of  protoxide  of  copper, 
and  traces  of  gold. 

1413.  The  pure  salt  is  soluble  in  its  own  weight  of  cold  and  in 
half  its  weight  of  hot  water.  It  dissolves  also  in  4 times  its  weight 
of  alcohol.  Its  aqueous  solution,  if  preserved  in  clear  glass  ves- 
sels, undergoes  little  or  no  change  even  in  the  direct  rays  of  the 
sun  ; but  when  exposed  to  light,  especially  to  sunshine,  in  contact 
with  paper,  the  skin,  or  any  organic  substance,  a black  stain  is  pro- 
duced, owing  to  decomposition  of  the  salt  and  reduction  of  its  oxide 
to  the  metallic  state.  This  change  is  so  constant,  that  this  salt 
constitutes  an  extremely  delicate  test  of  the  presence  of  organic 
matter.  Its  solution  is  a delicate  test  also  of  chlorine  and  hydro- 
chloric acid. 

1414.  Sulphur,  phosphorus,  charcoal,  hydrogen,  and  several  of 
the  metals,  decompose  this  nitrate. 

A few  grains  mixed  with  a little  sulphur,  and  struck  upon  an  anvil  with  a 
heavy  hammer,  produce  a detonation  ; phosphorus  occasions  a violent  explosion 
when  about  halt  a grain  of  it  is  placed  upon  a crystal  of  the  nitrate,  upon  an 
anvil,  and  struck  sharply  with  a hammer;  and  if  heated  with  charcoal,  it  defla- 
grates, and  the  metal  is  reduced. 

If  a piece  of  silk  dipped  into  a solution  of  nitrate  of  silver  be  exposed  while 
moist  to  a current  of  hydrogen  gas,  it  is  first  blackened,  and  afterwards  becomes 
iridescent  from  the  reduction  of  portions  of  the  metal/ * 

A stick  of  clean  phosphorus,  introduced  into  a solution  of  nitrate  of  silver, 
soon  becomes  beautifully  incrusted  with  the  metal,  which  separates  upon  it  in 
arborescent  crystals.  A plate  of  copper  occasions  a brilliant  precipitation  of 
silver,  and  the  copper  is  oxidized  and  dissolved  by  the  acid. 

The  precipitation  of  silver  by  mercury  produces  a peculiar  ar- 
rangement, called  the  arbor  Diana  (1244.) 

1415.  Nitrate  of  silver  is  employed  for  writing  upon  linen  under 
the  name  of  indelible  or  marking  ink, t and  is  an  ingredient  in  many 
of  the  liquids  which  are  sold  for  the  purpose  of  changing  the  col- 
our of  hair;  but,  when  thus  employed,  it  should  be  very  much  di- 
luted, and  used  with  extreme  caution. 

1416.  White  paper,  or  white  leather,  when  stained  with  a solution  of  nitrate 
of  silver,  in  the  proportion  of  ten  parts  of  water  to  one  of  the  salt,  undergoes 
no  change  in  the  dark;  but  when  exposed  to  the  light  of  day,  it  gradually  ac- 
quires colour,  and  passes  through  a succession  of  changes  to  black.  The  com- 
mon sun-beams,  passing  through  red  glass,  have  very  little  effect  upon  it;  yellow 
and  green  are  more  efficacious;  but  blue  and  violet  produce  the  most  decidedly 
powerful  effects.  Hence  this  property  furnishes  a method  of  copying  paintings 
on  glass,  and  transferring  them  to  leather  or  paper. t 


♦See  Mrs  Fulhame’s  Essay  on  Combustion. 

+ 100  grs.  of  the  nitrate  may  be  dissolved  in  distilled  water,  and  2 or  3 drachms  of 
mucilage  be  added.  The  preparatory  liquid  maybe  made  with  half  an  ounce  of  car- 
bonate of  soda  dissolved  in  2 or  3 ounces  of  water,  adding  half  an  ounce  of  mucilage. 
This  ink  is  discharged  by  chlorine  and  ammonia. 

t See  description  of  the  process  by  Wedgwood  in  Nicholson’s  Jour.  iii.  167,  and 
Talbot  on  Photogenic  drawing,  Lond.  and  Edin.  Phil.  Mag.  xiv. 


339 


Chlorate  of  Potassa. 

By  a similar  process,  ivory  may  be  covered  with  silver.  Let  a slip  of  ivory  Sect.  I.' 
be  immersed  in  a dilute  solution  of  pure  nitrate  of  silver,  till  the  ivory  has  ac-  g-|verjn  In- 
quired a bright  yellow  colour.  Then  remove  it  into  a tumbler  filled  with  dis-  • ° 

tilled  water,  and  expose  it  to  the  direct  light  of  the  sun.  After  two  or  three 
hours’  exposure,  it  will  have  become  black  ; but  on  rubbing  it  a little,  the  sur- 
face will  be  changed  into  a bright  metallic  one,  resembling  a slip  of  pure  silver. 

As  the  solution  penetrates  deep  into  the  ivory,  the  bright  surface  when  worn 
away,  is  replaced  by  a succession  of  others.  H.  2.  124. 

1417.  Nitrites. — Our  knowledge  of  the  compounds  of  nitrous 
acid  with  alkaline  bases  is  imperfect. 

1418.  Chlorates. — The  salts  of  chloric  acid  are  very  analogous  to  chlorates, 
the  nitrates.  As  the  chlorates  of  the  alkalies,  alkaline  earths,  and 

most  of  the  common  metals,  are  composed  of  1 eq.  of  chloric  acid 
and  1 eq.  of  a protoxide,  M0-|-C105,  it  follows  that  the  oxygen  of 
the  latter  to  that  of  the  former  is  in  the  ratio  of  1 to  5. 

1419.  The  chlorates  are  decomposed  by  a red  heat,  nearly  all  of  Decompo- 
thern  being  converted  into  metallic  chlorides,  with  evolution  of  pure  sedbyheat. 
oxygen  gas.  They  deflagrate  with  inflammable  substances  with 
greater  violence  than  nitrates,  yielding  oxygen  with  such  facility 

that  an  explosion  is  produced  by  slight  causes. 

Mix  a few  grains  of  sulphur  with  three  times  its  weight  of  chlorate  of  potas-  gXp 
sa,  wrap  the  mixture  in  tin  foil,  and  strike  it  forcibly  upon  an  anvil.* 

1420.  All  the  chlorates  are  soluble  in  water,  and  are  distin-  solubility 
guished  by  the  action  of  strong  hydrochloric  and  sulphuric  acids,  the  ofchlo- 
former  of  which  occasions  the  disengagement  of  chlorine  and  pro- rates- 
toxide  of  chlorine  (641),  and  the  latter  of  peroxide  of  chlorine 
(652).  t. 

1421.  Chlorate  of  Potassa.  This  salt,  formerly  called  oxymuriate  Chlorate  of 
or  hyper -oxijmuriate  of  potassa , is  formed  by  passing  chlorine  potassa. 
through  a solution  of  potassa.  Chloride  of  potassium  is  one  of  the 
results,  the  other  is  the  chlorate  of  potassa. 

This  salt  is  prepared,  upon  the  large  scale,  by  charging  Woulfe’s  bottles  (634  jqow  0b_ 
note),  with  solution  of  carbonate  of  potassa,  and  passing  chlorine  slowly  through  tained. 
it  :t  the  gas  is  absorbed,  and  the  liquor  effervesces  chiefly  from  the  escape  of  car- 
bonic acid;  when  this  has  ceased,  the  liquor  may  be  put  aside  in  a cold  dark 
place  for  about  24  hours,  when  it  will  be  found  to  have  deposited  a considerable 
portion  of  the  crystallized  chlorate  which  may  be  taken  out,  drained,  and  purified 
by  solution  in  hot  water,  which,  during  cooling  again,  deposits  the  salt  in 
white  crystalline  scales.  The  liquor  is  generally  of  a pinkish  hue,  from  the  pre- 
sence of  manganese. 4 

1422.  The  crystals  are  four  and  six  sided  scales,  of  a pearly  lustre.  Crystals. 
Its  forms,  according  to  Brooke,  belong  to  the  oblique  prismatic  sys- 
tem. It  is  soluble  in  16  times  its  weight  of  water  at  60°,  and  in  two 

and  a half  of  boiling  water.  It  is  anhydrous,  and  when  exposed  to 
a temperature  of  400°  or  500°,  fuses.  By  an  increase  of  heat,  nearly 
4)  to  redness,  pure  oxygen  gas  is  disengaged  (365-4). 

1423.  It  acts  very  energetically  upon  many  inflammables.  onlnflam' 

Rub  two  grains  into  powder  in  a mortar,  and  add  one  grain  of  sulphur.  Mix  mabieg, 

them  very  accurately,  by  gentle  triture,  and  then,  having  collected  the  mixture  Exp. 


* This  experiment  requires  caution,  and  is  made  more  safely  by  placing  the  mix- 
ture under  a long  bar  of  wood,  fitted  to  a groove,  which  can  be  driven  down  by  a 
smart  blow.  W. 

t The  tube  which  is  immersed  in  the  alkaline  solution,  should  be  at  least  half  an 
inch  in  diameter,  to  prevent  its  being  choaked  by  crystals  that  may  form, 
t See  another  process  by  Hayes  in  Amer.  Jour.,  xvii.  408. 


340 


Salts — Chlorates. 


Chap.  V. 
Exp. 

Action  of 
sulphuric 
acid. 


Exp. 


Exp. 


Caution. 


Chlorate  of 
baryta, 

Process. 


Crystals. 


M&tchr*. 


Percussion 

powder. 


Snbititu'ed  for 
nitre  in  gun- 
powder. 


to  one  part  of  the  mortar,  press  the  pestle  down  upon  it  suddenly,  and  forcibly. 

A loud  detonation  will  ensue. 

Mix  five  grains  of  the  salt  with  half  the  quantity  of  powdered  charcoal  in  a 
similar  manner.  On  triturating  the  mixture  strongly,  it  will  inflame,  especially 
with  the  addition  of  a grain  or  two  of  sulphur,  but  not  with  much  noise. 

1424.  When  sulphuric  acid  is  poured  upon  mixtures  of  this  salt 
and  combustibles,  instant  ignition  ensues  in  consequence  of  the  evo- 
lution of  peroxide  of  chlorine;  and  when  sulphuric  or  nitric  acids 
are  poured  upon  similar  mixtures  under  water  by  means  of  a long 
funnel,  inflammation  also  ensues. 

Mix  a 9mall  quantit)'  of  sugar  with  half  its  weight  of  the  salt,  and  on  the  mix- 
ture pour  a little  sulphuric  acid.*  A sudden  and  vehement  inflammation  will  be 
produced. 

Phosphorus  may  be  inflamed  under  the  surface  of  the  water,  by  means  of  this 
salt.  Put  into  a tall  wine  glass,  one  part  of  phosphorus  with  two  of  the  salt ; fill 
it  nearly  with  water,  and  slowly  pour  in,  by  means  of  a glass  tube,  reaching  to 
the  bottom,  three  or  four  parts  of  sulphuric  acid.  The  phosphorus  takes  fire,  and 
burns  vividly  under  the  water.  These  experiments  require  caution  lest  the  in- 
flamed substances  should  be  thrown  into  the  eyes.  Oil  may  also  be  thus  in- 
flamed on  the  surface  of  water,  the  experiment  being  made  with  the  omission  of 
the  phosphorus,  and  the  substitution  of  a little  olive  or  linseed  oil. 

1425.  Chlorate  of  potassa  should  not  be  kept  mixed  with  sulphur 
in  considerable  quantity,  as  the  mixture  may  explode  spontane- 
ously.! 

1426.  A few  grains  of  chlorate  of  potassa  put  into  a tea-spoonful 
of  hydrochloric  acid,  and  then  diluted  with  water,  form  an  extempo- 
raneous bleaching  liquor. 

1427.  Chlorate  of  Baryta  is  the  compound  employed  in  the  for- 
mation of  chloric  acid  (657.) 

The  readiest  mode  of  preparing  it  is,  to  digest  for  a few  minutes  a concentrated 
solution  of  chlorate  of  potassa  with  a slight  excess  of  silicated  hydrofluoric  acid, 
the  alkali  is  precipitated  in  the  form  of  an  insoluble  double  fluoride  of  silicon 
and  potassium,  while  chloric  acid  remains  in  solution.  The  liquid  after  filtra- 
tion is  neutralized  by  carbonate  of  baryta,  which  throws  down  the  excess  of  sili- 
cated hydrofluoric  acid,  and  chlorate  of  baryta  is  left  in  solution 

By  evaporation  it  yields  prismatic  crystals,  requiring  for  solution 
four  times  their  weight  of  cold,  and  a still  smaller  quantity  of  hot 
water.  They  are  composed  of  76.7  parts  1 eq.  of  baryta,  75.42  I 
eq.  of  chloric  acid,  and  9 or  1 eq.  of  water.  T.  677. 

* A mixture  of  this  kind  is  the  basis  of  matches,  for  the  purpose  of  procuring  instan- 
taneous light-  The  bottle  into  which  they  are  dipped,  contains  concentrated  sulphuric 
acid  which  is  prevented  from  escaping  by  a quantity  o!  finely  spun  glass  or  the  fibres 
of  amianthus.  30  parts  of  powdered  chlorate  of  potassa,  10  cf  powdered  sulphur,  8 of 
sugar,  5 of  gum  arahic.  and  a little  cinnabar.  Tne  sugar,  gum,  and  salt  are  first  rub- 
bed together  into  a paste  with  sufficient  water;  the  sulphur  is  then  added,  and  the 
whole  being  well  beaten  together,  small  brimstone  matches  are  dipped  in,  so  as  to  retain 
a thin  coat  of  the  mixture  upon  their  sulphuretted  points.  ^ 

A very  convenient  method  of  obtaining  a flame,  is  to  dip  the  end  of  a piece  of  paper  “ 
in  spirits  of  turpentine,  drop  upon  it  a few  scales  of  the  salt,  aud  then  a drop  of  sul- 
phuric acid 

One  of  the  compounds  occasionally  employed  in  percussion  gun-locks  contains  this 
salt ; 10  parts  of  gunpowder  are  rubbed  with  water,  and  the  soluble  part  poured  off; 
the  remaining  paste  is  then  mixed  with  5$  parts  of  finely  powdered  chlorate  of  potassa, 
and  a drop  of  it  put  into  each  of  the  small  copper  caps  adapted  to  the  peculiar  touch- 
hole  of  the  gun.  The  great  disadvantage  of  this  compound  is  that  it  forms  products 
which  corrode  the  toucnhole;  lulminating  mercury  is  preferable. 

t It  was  proposed  by  Berthollet  to  substitute  this  salt  for  nitre,  in  the  preparation 
of  gunpowder  and  the  attempt  was  made  at  Essone  in  1788  ; but,  as  might  have  been 
expected,  no  sooner  was  the  mixture  of  the  chlorate  with  the  sulphur  and  charcoal 
submitted  to  trituration  than  it  exploded  with  violence,  and  proved  fatal  to  several 
people. 


Iodates. 


341 


1428.  Perchlorates.  The  neutral  proto-salts  of  perchloric  acid  Sect-  r 
consist  of  1 eq.  acid  and  base,  as  is  expressed  by  the  formula  MO+  Perchlo- 
C1207.  Most  of  these  salts  are  deliquescent,  very  soluble  in  water, rates- 
and  soluble  in  alcohol.  Heated  to  redness  they  yield  oxygen  gas  Effect  of 
and  metallic  chlorides  ; and  they  are  distinguished  from  the  chlorates  heat. 

by  not  acquiring  a yellow  tint  on  the  addition  of  hydrochloric  acid. 

1429.  The  solubility  in  alcohol  of  the  perchlorates  of  baryta,  soda,  Solubility 
and  oxide  of  silver,  is  a property  which  the  analytical  chemist  may  af(^°  ° 
avail  himself  of  in  analysis,  for  the  separation  of  potassa  and  soda 

from  each  other. 

1430.  Chlorites.  The  alkaline  salts  of  chlorous  acid  are  readily  Chlorites, 
made  by  transmitting  a current  of  chlorous  acid  gas  into  a solution 

of  the  pure  alkalies.  They  are  soluble  in  water,  and  are  remarkable 
for  their  bleaching  and  oxidizing  properties.  By  the  latter  proper-  Recog- 
ties  and  the  evolution  of  chlorous  acid  on  the  addition  of  any  of  the  nised. 
stronger  acids  their  presence  is  readily  recognised. 

1431.  Hypochlorites.  The  hypochlorites  may  be  produced  by  the  Hypochlo- 
addition  of  chlorine  gas  on  the  salifiable  bases.  The  most  impor-  rites, 
tant  of  them  is  hypochlorite  of  lime,  the  well  known  bleaching 
powder  (901).  During  absorption  of  the  chlorine,  chloride  of  calci- 
um and  hypochlorite  of  lime  are  produced  in  equivalent  propor- 
tions.^ 

1432.  It  is  a dry  white  powder,  with  the  odour  of  chlorine  and  a Bleaching 
strong  taste.  It  dissolves  partially  in  water  and  the  solution  bleaches  ; powder, 
it  contains  both  chlorine  and  lime;  the  undissolved  portion  is  hy- 
drate of  lime,  retaining  a small  quantity  of  chlorine.  The  solution 

is  decomposed  by  exposure,  its  chlorine  being  set  free,  and  carbonate 
of  lime  generated. 

1433.  It  is  largely  employed  in  bleaching,  for  the  purpose  of  re-  Uses, 
moving  offensive  odours,  and  of  arresting  putrefaction.!  With  hy- 
drochlorate of  ammonia  it  affords  nitrogen  gas  from  the  decomposi- 
tion of  the  ammonia  (420). 

Into  a small  tubulated  retort  introduce  the  bleaching  salt,  add  sufficient  water 
to  bring  it  to  the  consistence  of  cream;  drop  in  lumps  of  the  hydrochlorate  of 
ammonia  ; effervescence  will  take  place,  and  the  nitrogen  be  disengaged. 

1434.  Iodates.  The  general  character  of  the  iodates  is  similar  to  Iodates, 
that  of  the  chlorates.  In  all  neutral  protiodates  the  oxygen  contained  ^jec^|reancer' 
in  the  oxide  and  acid  is  in  the  ratio  of  1 to  5.  They  deflagrate  with  ler) 
combustibles,  and  yield  oxygen  gas  at  a red  heat,  a metallic  iodide 
remaining. 

1435.  The  iodates  are  recognised  by  the  facility  with  which  their  Bycog- 
acid  is  decomposed  by  deoxidizing  agents.  Hydrosulphnric  acid  oc- ruse 
casions  the  formation  of  hydriodic  acid,  by  y^ielding  hydrogen  to  the 
iodine.  Hence  an  iodate  of  potassa  may  be  converted  into  the  iodide 

by  transmitting  a current  of  HS  through  its  solution.  The  iodates 
are  very  sparingly  soluble,  or  actually  insoluble  in  water,  excepting 
the  iodates  of  the  alkalies. 

1438.  Iodate  of  Potassa  may  be  procured  by  adding  iodine  to  a Todate  of 
concentrated  hot  solution  of  pure  potassa,  until  the  alkali  is  com-P°tassa’ 
pletely  neutralized. 

* Turner. 

t For  details  respecting  its  manufacture,  &c.,  see  Ure’s  Did.  of  Arts,  &c.,  and  for 
the  methods  of  estimating  the  value  of  this  substance,  see  page  243. 


342 


Chap.  V. 


Process, 


Another. 


Henry’s. 


Use. 


Phos- 

phates. 


Three  fam- 
ilies. 


Protophos- 

phates. 

Triphos- 

phates. 


Effect  of 
heat. 


Soluble 

phosphates 

detected, 


FcrrtuU. 


W Her  a base. 


Test  of  phos- 
phoric aciJ. 


Salts — Phosphates. 

The  liquid,  which  contains  an  iodate  and  iodide  is  evaporated  to  dryness  by 
" a gentle  heat,  and  the  residue,  when  cold,  is  treated  by  repeated  portions  of  boil- 
ing alcohol.  The  iodate,  which  is  insoluble  in  that  menstruum,  is  left,  while 
the  iodide  of  potassium  is  dissolved. 

A better  process  is  founded  on  the  property  which  iodide  of  potassium  pos- 
sesses, of  absorbing  oxygen  while  in  the  act  of  escaping  from  decomposing  chlo- 
rate of  potassa.  For  this  purpose, 

Iodide  of  potassium  is  fused  in  a capacious  Hessian  crucible,  and  when,  after 
removal  from  the  fire,  it  is  yet  semi-fluid,  successive  portions  of  pulverized  chlo- 
rate of  potassa  are  projected  into  it,  stirring  well  after  each  addition.  The  ma- 
terials froth  up  considerably,  and  when  the  action  is  over,  a white,  opaque, 
cellular  mass  remains,  easily  separable  from  the  crucible;  tepid  water  dissolves 
out  the  chloride  of  potassium,  and  leaves  the  iodate.  Convenient  proportions 
are  one  part  of  iodide  of  potassium  and  rather  more  than  one  and  a half  of  chlo- 
rate of  potassa.* 

1437.  From  this  salt  all  the  insoluble  iodates  may  be  procured  by 
double  decomposition.  Thus  iodate  of  baryta  may  be  formed  by*  | 
mixing  chloride  of  barium  with  a solution  of  iodate  of  potassa. 

The  Bromates  have  many  characters  in  common  with  the  chlo- 
rates and  iodates.  t. 

1438.  Phosphates.  As  there  are  three  isomeric  modifications  of  1 
the  same  acid,  which  have  been  described  under  the  names  of  phos- 
phoric, pyrophosphoric , and  vietaphosphoric  acid  (page  174),  it  is  ne- 
cessary to  have  three  corresponding  families  of  salts,  the  phosphates,  i 
pyrophosphates  and  metaphosphates .t 

1439.  All  the  protophosphates  which  are  neutral  in  composition  are 
soluble  in  water,  and  redden  litmus  paper ; whence  they  are  com- 
monly called  superphosphates.  The  triphosphates,  except  those  j 
of  the  pure  alkalies,  are  either  sparingly  soluble  or  insoluble  in  wa- 
ter ; but  they  are  all  dissolved  bv  dilute  nitric  or  phosphoric  acid, 
being  converted  into  the  soluble  phosphates.  All  the  triphosphates 
with  fixed  and  strong  bases  bear  a red  heat  without  change  ; but  the 
phosphates  and  diphosphates,  to  judge  from  experiments  on  the  soda  : 
salts,  are  converted  into  metaphosphates  and  pyrophosphates.  Most 
of  the  phosphates  of  the  second  class  of  metals  are  resolved  into  | 
phosphurels  by  the  conjoint  agency  of  heat  and  combustible  matter. 

The  phosphates  of  the  alkalies  are  only  partially  decomposed  un- 
der these  circumstances,  and  the  phosphates  of  baryta,  strontia,  and 
lime,  undergo  no  change. 

1440.  The  presence  of  a soluble  phosphate  may  be  distinguished 
by  the  test  for  phosphoric  acid-t 

The  insoluble  phosphates  are  decomposed  when  boiled  with  a 


* Jour,  de  Phar.,  July,  1832 

t An  cquiv.  of  each  of  the  three  acids,  is  a compound  of  31. 4 parts  or  2 eq.  of  phos- 

Jihorus  -f-  40  parts  or  5 eq.  of  oxygen  = 71.4,  expressed  by  the  formula  P2!)5.  To 
brm  a salt  neutral  in  composition  1 eq.  of  an  alkaline  base  is  requisite,  and  in  the  case 
of  any  protoxide,  indicated  by  MO.  the  general  formula  will  be  MO-f-FHJ5.  If  2 eq. 
of  a protoxide  are  united  with  one  of  the  acid,  we  have  a disalt,  2MCH-P205;  and  if  3 
eq.  of  a base  combine  with  1 eq.  of  the  acid,  it  is  a trisalt , 3M04-P205.  It  seems  also 
that  water  plays  the  part  of  an  alkaline  base  towards  each  of  the  three  acids,  either 
alone  or  conjointly  with  another  base;  the  salts  with  such  compound  bases  can 
scarcely  he  viewed  in  the  light  of  double  salts,  since  the  two  bases  act  together  as  one 
electro-positive  element. 

t When  phosphoric  acid  is  neutralized  by  ammonia  and  mixed  with  nitrate  of  oxide 
of  silver,  the  yellow  phosphate  of  that  oxide  subsides,  a character  by  which  it  is  dis- 
tinguished from  all  adds,  except  the  arsenious.  T.  316. 


343 


Triphosphates . 

strong  solution  of  carbonate  of  potassa  or  soda,  the  acid  uniting  with  Sect,  i. 
the  alkali  so  as  to  form  a soluble  phosphate  ; the  earthy  phosphates  Insoluble, 
require  continued  ebullition,  and  should  preferably  be  fused  with  an  decompo- 
alkaline  carbonate,  like  an  insoluble  sulphate,  t. 

1441.  Triphosphate  of  Soda.  3N0-j-P205,  93.9  3 eq.  base  -f-  . 

71.4  1 eq.  acid  = 165.3 ; in  crystals  with  216  or  24  eq.  water  = Soda,°S 
381.3.  This  salt  is  made  by  adding  pure  soda  to  a solution  of  the  Process, 
succeeding  compound  until  the  liquid  feels  soapy  to  the  fingers,  an 
excess  of  soda  not  being  injurious.  The  liquid  is  then  evaporated 

until  a pellicle  appears,  and  the  crystals  which  form  on  cooling  are 
quickly  redissolved  in  water  and  recrystallized. 

1442.  The  crystals  are  colourless  six-sided  prisms,  with  a strong  properties, 
alkaline  taste  and  reaction,  requiring  five  times  their  weight  of  wa- 
ter at  60°  for  solution.  They  fuse  at  170°,  and  may  be  exposed  to 

a red  heat,  without  losing  their  characters  of  a phosphate.  The 
feeblest  acids  deprive  the  salt  of  one  third  of  its  soda. 

1443.  Triphosphate  of  Soda  and  Basic  Water.  2NaO.HQ-|-  Triphos- 
P O5,  62.6  2 eq.  soda,  9 l eq.  water  -f-  71.4  1 eq.  acid  = 143  ; in  goda^and 
crystals  with  216  or  24  eq.  water  ='  359,  with  135  or  15  eq.  water  basic  wa- 
— 278.  This  salt  is  the  most  common  of  the  phosphates, .'being' p^cess 
manufactured  on  a large  scale  by  neutralizing  with  carbonate  of  soda 

the  acid  phosphate  of  lime  procured  by  the  action  of  sulphuric  acid 
on  burned  bones  (p.  169).  It  is  generally  described  as  the  neutral 
phosphate  of  soda. 

1444.  It  crystallizes  best  out  of  an  alkaline  solution  ; but  however  crystals, 
prepared  is  always  alkaline  to  test  paper.  The  crystals  effloresce, 

and  require  four  times  their  weight  of  cold,  and  twice  their  weight 
of  hot  water  for  solution. 

1445.  Acid  Triphosphate  of  Soda  and  Basic  Water.  NaO.  2HO  AcidTriph. 
-f-P205,  31.3  1 eq.  sod.  18  2 eq.  water  -f-  71.4  1 eq.  acid  *=  120.7  ; and 

in  crystals  with  18  or  2 eq.  water  = 138t7.  This  salt,  commonly  water‘ 
called  biphosphate  of  soda,  may  be  formed  by  adding  phosphoric  acid 
to  a solution  of  carbonate  of  soda,  or  to  either  of  the  preceding  phos- 
phates, until  it  ceases  to  give  a precipitate  with  chloride  of  barium.  Crystals. 
Being  very  soluble  in  water,  the  solution  must  be  concentrated  in 
order  that  it  may  crystallize.  This  salt  is  capable  of  yielding  two 
different  kinds  of  crystals  without  varying  its  composition.^ 

1446.  Triphosphate  of  Soda,  Oxide  of  Ammonium,  and  Basic 

Water,  NaO., H4NO.  HG+P205,  31.3  1 eq  soda,  26.15  1 eq.  ox. 
am.  9 1 eq.  water  -j-  71.4  1 eq.  acid  .==  137.85  eq.  ; in  crystals 
with  72  or  8 eq.  water  =209.85.  Prepared  by  mixing  1 eq.  of 

hydrochlorate  of  ammonia  and  2 eq.  of  the  neutral  phosphate  of 
soda,  each  being  previously  dissolved  in  a .small  quantity  of  boiling 
water.  It  has  been  long  known  as  microcosmic  salt,  and  is  much  mic  salt*" 


* For  which  see  Liebig  and  Turner’s  Elem.  684. 

Triphosphate  of  Potassa.  3KO+P205,  141.45  3 eq.  base  + 71.4  1 eq.  acid  = 
212.85.  Formed  by  adding  caustic  potassa  in  excess  lo  a solution  of  phosphoric  acid. 

Triphosphate  of  Potassa  and  Basic  Water.  2K0.HQ+P205,  94.3  2 eq.  KO,  9 1 eq. 
HO  -j-  71.4  1 eq.  acid  — 174.7.  Prepared  by  neutralizing  the  superphosphate  of  lime 
from  bones  with  carbonate  of  potassa. 

Acid  Triphosphate  of  Potassa  and  Basic  Water.  KO2HO+P2O5,  47.15  1 eq.  pot. 
18  2 eq.  water  + 71.4  1 eq.  acid  — 136.55  eq.  Formed  by  adding  phosphoric  acid  to 
carbonate  of  potassa  until  the  liquid  ceases  to  give  a precipitate  with  chloride  of  bari- 
um, and  setting  aside  to  crystallize. 


344 


Chap.  V. 


Phosphates 
of  lime, 


Triphos- 

phate, 


Acid  tri- 
phosphate 
and  basic 
water. 


Of  magne- 


Phosphate 
of  ammonia 
and  magne- 
sia. 


Salts — Triphosphates. 

employed  in  experiments  with  the  blotv-pipe.  When  heated  it  parts 
with  its  water  and  ammonia,  and  a very  fusible  metaphosphate  of 
soda  remains.* 

1447.  Phosphates  of  Lime.  The  peculiar  compound  called  the 
bone  phosphate ,t  exists  in  bones  after  calcination,  and  falls  as  a gela- 
tinous precipitate  on  pouring  chloride  of  calcium  into  a solution  of 
the  rhombic  phosphate  of  soda,  or  on  adding  ammonia  to  a solution 
of  any  phosphate  of  lime  in  acids. t 

1448.  Triphosphate  of  Lime  and  Basic  Water , 2CaO.  HO-f- 
FO5,  57  2 eq.  lime,  9 1 eq.  water  -f-  71.4  1 eq.  acid  = 137.4  eq. 
This  salt  is  commonly  called  neutral  phosphate ; it  falls  as  a 
granular  precipitate  when  the  rhombic  phosphate  of  soda  is  added 
drop  by  drop  to  chloride  of  calcium  in  excess.  The  triphosphate  of 
lime  occurs  in  the  mineral  called  apatite. 

1449.  Acid  Triphos.  of  Lime  and  Basic  Water , Ca02H0  -j- 
FO3,  28.5  1 eq.  lime,  IS  2 eq.  water  -(-71.4  1 eq.  acid  = 117.9. 
This  is  called  the  biphosphate  from  its  acid  reaction,  and  is  formed 
by  dissolving  either  of  the  preceding  salts  in  a slight  excess  of  phos- 
phoric acid.  It  exists  in  the  urine. 

1450.  Triphosphate  of  Magnesia  and  Basic  Water,  is  formed 
by  mixing  hot  saturated  solutions  of  the  rhombic  phosphate  of  soda 
and  sulphate  of  magnesia,  and  separates  on  cooling  in  small  crys- 
tals which  contain  13  eq.  of  water  to  1 of  the  salt. 

1451.  The  phosphate  of  ammonia  and  magnesia , subsides  as  a 
pulverulent  granular  precipitate  from  neutral  or  alkaline  solutions, 
containing  phosphoric  acid,  ammonia,  and  magnesia.  It  is  readily 
dissolved  by  acids  and  is  sparingly  soluble  in  pure  water,  especially 
when  carbonic  acid  is  present ; but  it  is  insoluble  in  a solution  of 
most  neutral  salts,  such  as  hydrochlorate  of  ammonia.  It  consti- 
tutes one  variety  of  urinary  concretions,  according  to  Berzelius  it 
consists  of 

Phosphoric  acid  . 71.4 

Magnesia  . 41.4 

Ammonia  . 34.3 

Water  90 


1 eq. 

2 eq. 


10  eq. 


POo. 

2MgO. 

2H3N. 

1HO. 


Effect  of 
beat. 


Triphos- 
phate of 
silver. 


1452.  By  a red  heat  it  loses  its  water  and  ammonia,  and  the 
residue  is  diphosphate  of  magnesia,  which  contains  36.67  per  cent, 
of  pure  magnesia.  At  a strong  red  heat  it  fuses,  and  appears  when 
cold  as  a white  enamel. 

1453.  Triphosphate  of  Oxide  of  Silver  subsides,  of  a character- 
istic yellow  colour,  (1440)  when  the  rhombic  phosphate  of  soda  is 

mixed  in  solution  with  nitrate  of  oxide  of  silver,  N being  set  free  at 

the  same  time.  This  salt  is  very  soluble  in  N and  P,  forming  the 


* Triphosphate  of  Oxide  of  Am.  and  Basic  M ater,  2IPNO-  HO  P205,  52.30  2 
eq.  ox.  Am.  9*1  eq  water  + 71.4  l eq.  acid  = 132-70  eq.,  formed  hy  adding  ammo- 
nia to  concentrated  phosphoric  acid  until  a precipitate  appears.  On  applying  heat, 
the  precipitate  is  dissolved,  and  on  abandoning  the  solution  to  itself,  the  neutrai  salt 
crystallizes-  The  crystals  are  oblique  rhombic  prisms,  the  smaller  angle  being  84° 
30/. 

t Bone  Phosphate  of  Lime , 8Ca0-f-3P-*05,  223  8 eq.  base  + 214.2  3 eq.  acid  = 
442.2  eq. 

t Triphosphate  of  Lime,  3Ca0+P205,  85.5  3 eq.  base  + 71.4  1 eq.  acid  = 156.9. 


Chromates . 


345 


soluble  phosphate  and  in  ammonia.  It  is  blackened  by  exposure  to  Sect,  i. 
light. 

1454.  When  phosphoric  acid,  with  the  aid  of  heat  is  made  to 
combine  with  2 eq.  either  of  water  or  some  fixed  base,  the  modifica- 
tion of  phosphoric  acid,  termed  pyrophosphoric  (569)  is  procured.  Pyrophos- 

Combined.  with  bases  it  forms  pyrophosphates*  phates. 

1455.  The  oxides  of  most  metals  of  the  second  class  yield  with 
this  acid  insoluble  or  sparingly  soluble  salts,  which  may  be  pre- 
pared by  double  decomposition  with  dipyrophosphate  of  soda-t 

1456.  Arseniates . Arsenic  acid  resembles  the  phosphoric  in  com-  Arseniates. 
position  and  in  many  of  its  properties.  It  forms  tribasic  salts.  Those 

with  2 eq.  of  basic  water  are  soluble  in  water  and  redden  litmus; 
with  1 eq.  of  basic  water,  in  which  the  oxygen  of  the  alkaline  base 
and  acid  is  as  2 to  5,  the  salt  is  usually  called  a neutral  arseniate. 

When  no  basic  water  is  present,  the  salt  is  usually  described  as  a 
subarseniate. 

1457.  Many  of  the  arseniates  bear  a red  heat  without  decomposi-  Effect  of 
tion,  but  they  are  all  decomposed  when  heated  to  redness  along  with  heat- 
charcoal,  metallic  arsenic  being  set  at  liberty. 

The  soluble  arseniates  are  easily  recognised  by  the  tests  for  arsenic  Arseniates 
(1053),  and  the  insoluble  arseniates,  when  boiled  in  a strong  solu-  recognised, 
tion  of  the  fixed  alkaline  carbonates,  are  deprived  of  their  acid, 
which  may  then  be  detected  in  the  usual  manner.  The  free  alkali, 
however,  should  first  be  exactly  neutralized  by  pure  nitric  acid. 

1458.  Arsenites.  The  arsenites  of  potassa,  soda,  and  ammonia,  Arsenites. 
may  be  prepared  by  acting  with  those  alkalies  on  arsenious  acid; 

they  are  very  soluble  in  water,  have  an  alkaline  reaction,  and  have  ProPerties* 
not  been  obtained  in  regular  crystals.  Most  of  the  other  arsenites 
are  insoluble,  or  sparingly  soluble,  in  pure  water  ; but  they  are  dis- 
solved by  an  excess  of  their  own  acid,  with  great  facility  by  N,  and 
by  most  other  acids  with  which  their  bases  do  not  form  insoluble 
compounds.  The  insoluble  arsenites  are  easily  formed  by  double 
decomposition. 

1459.  All  the  arsenites  are  decomposed  when  heated  in  close 
vessels,  the  arsenious  acid  being  either  dissipated  in  vapour,  or  con- 
verted, with  disengagement  of  some  metallic  arsenic,  into  arseniates. 

Heated  with  charcoal  or  black  flux,  the  acid  is  reduced  (1054.) 

1460.  The  soluble  arsenites,  if  quite  neutral,  are  characterized  by  Soluble  ar- 
forming  a yellow  arsenite  of  oxide  of  silver  when  mixed  with  the  senites  dis- 
nitrate  of  that  base,  and  a green  arsenite  of  protoxide  of  copper, tinguis  e 
Scheele's  green , with  sulphate  of  that  oxide.  When  acidulated  with  Schoeie,s 
acetic  or  hydrochloric  acid,  hydrosulphuric  acid  gas  causes  the  forma- 

tion  of  orpiment.  The  insoluble  arsenites  are  all  decomposed  when 
boiled  in  a solution  of  carbonate  of  potassa  or  soda.  The  arsenite 
of  potassa  is  the  active  principle  of  Folder's  arsenical  solution. 

1461.  Chromates.  The  salts  of  chromic  acid  are  mostly  either  Chromates, 
of  a yellow  or  red  colour,  the  latter  tint  predominating  whenever 


* For  which  see  Turner  and  Liebig’s  Elem.  687. 

+ For  description  of  Metaphosphates  see  T.  and  L.  Elem.  6S9  ; and  Graham  in 
Philos.  Trans.  1833,  part  2d. 

44 


346 


Salts — Borates. 


Chap  V. 

Effect  of 
heat, 


Anil  com- 
bustibles. 


Distin- 

guished. 


Chromate 
of  poiassa. 


Properties. 


Bichro- 

mate. 


Crystals. 


Insoluble 

chromates. 

Chromate 
of  lead. 
Borates. 


Dichromate. 


Process. 


the  acid  is  in  excess.  The  chromates  of  oxides  of  the  second  class 
of  metals  are  decomposed  by  a strong  red  heat,  by  which  the  acid  is 
resolved  into  the  green  oxide  of  chromium  and  oxygen  gas  ; but  the 
chromates  of  the  fixed  alkalies  sustain  a very  high  temperature 
without  decomposition.  They  are  all  decomposed  by  the  united 
agency  of  heat  and  combustible  matter.  The  neutral  chromates  of 
protoxides  are  similar  in  constitution  to  the  sulphates,  being  formed 
of  1 eq.  of  the  base  and  l of  chromic  acid,  the  formula  being  MO+ 
CrO3. 

1462.  The  chromates  are  in  general  sufficiently  distinguished  by 
their  colour.  They  may  be  known  chemically  by  the  following 
characters  : on  boiling  a chromate  in  hydrochloric  acid  mixed  with 
alcohol,  the  chromic  acid  is  at  first  set  free,  and  is  then  decomposed, 
a green  solution  of  the  chloride  of  chromium  being  generated. 

1463.  Chromates  of  Potassa.  The  neutral  chromate  from  which 
all  the  compounds  of  chromium  are  directly  or  indirectly  prepared, 
is  made  by  heating  to  redness  the  native  oxide  of  chromium  and 
iron,  chromate  of  iron,  with  nitrate  of  potassa  (1077),  when 
chromic  acid  is  generated,  and  unites  with  the  alkali  of  the  nitre. 

1464.  Chromate  of  potassa  has  a cool,  bitter  and  disagreeable 
taste  ; it  is  soluble  to  great  extent  in  boiling  water,  and  in  twice  its 
weight  of  that  liquid  at  60°;  but  it  is  insoluble  in  alcohol.  Ac- 
cording to  Thomson  it  is  neutral  in  composition,  consisting  of  52 
parts  or  1 eq.  of  chromic  acid,  and  47.15  parts  or  1 eq.  of  potassa.* 

1465.  Bichromate  of  Potassa  is  made  in  large  quantity  for  dye- 
in?*  .by  acidulating  the  neutral  chromate  with  sulphuric,  or  still  bet- 
ter with  acetic  acid,  and  allowing  the  solution  to  crystallize  by 
spontaneous  evaporation.  When  slowly  formed  it  is  deposited  in 
four-sided  tabular  crystals,  the  form  of  which  is  an  oblique  rhombic 
prism.  They  have  a rich  red  colour,  are  anhydrous,  and  consist  of 
1 eq.  of  the  alkali,  and  2 eq.  of  chromic  acid.t  They  are  soluble 
in  about  ten  times  their  weight  of  water  at  60°,  and  the  solution 
reddens  litmus  paper. 

1466.  The  insoluble  salts  of  chromic  acid  such  as  the  chromates 
of  baryta  and  oxides  of  zinc,  lead,  mercury  and  silver,  are  prepared 
by  mixing  the  soluble  salts  of  those  bases  with  a solution  of  chro- 
mate of  potassa.  The  yellow  chromate  of  lead  is  much  used  as  a 
pigment,  it  consists  of  1 eq.  of  acid  and  1 eq.  of  oxide. t 

1467.  Borates.  Boracic  acid  is  a feeble  acid  and  neutralizes  im- 
perfectly, hence  the  borates  of  soda,  potassa  and  oxide  of  ammo- 
nium hare  always  an  alkaline  reaction.  For  the  same  reason,  when 
the  borates  are  digested  in  any  of  the  more  powerful  acids,  the  bo- 


* Ann.  of  Philos,  xvi.  t Thomson. 

t The  chromate  of  oxide  of  zinc  may  be  used  for  the  same  purpose.  A dichromate 
composed  of  1 eq.  chromic  acid  and  2 ea-  protox.  lead,  may  be  formed  by  boiling  the 
carbonate  of  that  oxide  with  excess  of  chromate  of  potassa.  It  is  of  a beautiful  red 
colour,  and  has  been  recommended  as  a pigment  {Ann.  Philos,  xxv.  303.)  It  may 
also  be  made  by  boiling  the  neutral  chromate  with  ammonia  or  lime  water ; or  by 
fusing  nitre  at  a low  red  heat,  and  adding  chromate  of  oxide  of  lead  by  degrees  un- 
til the  nitre  is  nearly  exhausted.  The  chromate  of  potassa  and  nitre  are  then  re- 
moved by  water,  and  the  dichromate  is  left  crystalline  in  texture,  and  of  a beautiful 
tint.  ( Pog . An.  xxi.  580.)* 

* For  Chromates  of  Silver,  and  of  Chloride  of  Potassium,  see  T.  and  L.  Elem.  695. 


347 


Carbonate  of  Potassa. 

tacic  acid  is  separated  from  its  base.  But  at  a red  heat  this  acid  Se&t- l- 
decomposes  all  salts,  the  acid  of  which  is  volatile. 

1463.  The  borates  of  the  alkalies  are  soluble  in  water,  but  most  Properties, 
of  the  salts  of  this  acid  are  of  sparing  solubility.  They  are  not  de-  &c- 
composed  by  heat,  and  the  alkaline  and  earthy  borates  resist  the 
action  of  heat  and  combustible  matter.  They  are  remarkably  fusi* 
ble,  a property  owing  to  the  great  fusibility  of  the  acid  itself. 

1469.  The  borates  are  distinguished  by  the  following  character  : Distin- 
by  digesting  any  borate  in  a slight  excess  of  strong  sulphuric  acid,  Suished. 
evaporating  to  dryness,  and  boiling  the  residue  in  strong  alcohol,  a 
solution  is  formed  which  has  the  property  of  burning  with  a green 
flame. 

1470.  Biborate  of  Soda— -Borax.  This  salt,  which  has  been  Borax, 

very  long  known,  is  imported  from  India  in  the  impure  state,  under 

the  name  of  Tincal , which,  after  being  purified,  constitutes  the 
refined  borax  of  commerce.  It  is  frequently  called  sub-borate  of 
soda. 

1471.  It  crystallizes  in  prisms  of  the  oblique  system,  which  efflor-  Crystals, 
esce  ; they  require  20  parts  of  cold,  and  6 of  boiling  water,  for  so- 
lution. Exposed  to  heat  the  crystals  lose  their  water  of  crystalliza- 
tion, fuse,  and  then  form  a vitreous  substance  called  glass  of  borax. 

The  crystals  are  composed  of  69.8  parts  or  2 eq.  of  acid,  31.3  or 
1 eq.  soda,  and  90  or  10  parts  of  water. 

1472.  The  chief  use  of  borax  is  as  a flux,  and  for  the  preparation  Use. 
of  boracic  acid.^ 

1473.  Carbonates . The  carbonates  are  distinguished  by  being  de-  Carbon- 
composed  with  effervescence,  owing  to  the  escape  of  C,  by  nearly  actersof, 
all  the  acids ; and  all  of  them,  except  the  carbonates  of  potassa,  so- 

da  and  lithia,  may  be  deprived  of  their  acid  by  heat.  The  carbo- 
nates of  baryta  and  strontia,  especially  the  former,  require  an  in- 
tense heat  for  decomposition  ; those  of  lime  and  magnesia  are  re- 
duced to  the  caustic  state  by  a full  red  heat ; and  the  other  carbo- 
nates part  with  their  carbonic  acid  when  heated  to  dull  redness. 

1474.  All  the  carbonates,  except  those  of  potassa,  soda  and  am-  Solubility, 
monia,  are  of  sparing  solubility  in  pure  water;  but  all  of  them  are 

more  or  less  soluble  in  an  excess  of  carbonic  acid,  owing  probably 
io  the  formation  of  supersalts.  Several  of  the  carbonates  occur  na- 
tive. , 

1475.  Carbonate  of  Potassa,  KO+CO!,  47.15  1 eq.  base+22.12 
1 eq.  acid  = 69  27  eq.  This  is  a salt  of  great  importance  in 
many  arts  and  manufactures,  and  is  known  in  commerce  in  differ- 
ent states  of  purity,  under  the  names  of  wood-ash , pot-ash,  and  pearl- 
ash.  It  is  the  subcarbonate  of  potassa  of  the  U.  S.  Pharmacop. 

The  simplest  mode  of  showing  the  absorption  of  carbonic  acid  by  potassa,  is  Exp. 
the  following : Fill  a common  phial  with  carbonic  acid  gas  over  water ; and 

* The  Boracite  of  mineralogists  is  a biborate  of  magnesia.  A new  biborate  of  New  biborate  of 
soda,  containing  half  as  much  water  of  crystallization  as  the  above,  has  been  des-  ssda. 
cribed.  It  is  harder  and  denser  than  borax,  is  not  efflorescent,  and  crystallizes  in  oc- 
tohedrons.  It  is  made  by  dissolving  borax  in  boiling  water  until  the  sp.  gr.  of  the  Process 
solution  is  at  30°  or  32°  of  Beaume’s  hydrometer  5 the  solution  is  then  very  slowly 
cooled,  and  when  the  temperature  falls  to  about  133°  the  salt  is  deposited.  It  is 
found  to  be  more  convenient  for  the  use  of  jewellers  than  common  borax.  Ann.  de 
Chim.  et  Phy.  xxxvii.  419. 


348 


Sa  Its — Carbonates . 


Chap.  V. 


Exp. 


Effect  of 
heat. 


Sources  of 
potassa. 


Bicarbon- 

ate, 

Formed. 


Properties. 


Carbonate 
of  soda. 


Sources  of. 


when  full,  stop  it  by  applying  the  thumb.  Then  invert  the  bottle  in  a solution 
of  pure  potassa  contained  in  a cup,  and  rather  exceeding  in  quantity  what  is 
sufficient  to  fill  the  bottle.  The  solution  will  rise  into  the  bottle,  and  if  the  gas 
be  pure,  will  fill  it  entirely.  Pour  out  the  alkaline  liquor,  fill  the  bottle  with  wa- 
ter, and  again  displace  it  by  the  gas.  Proceed  as  before,  and  repeat  the  process 
several  times.  It  will  be  found  that  the  solution  will  condense  many  times  its 
bulk  of  the  gas  ; whereas  water  combines  only  with  its  own  volume. 

This  experiment  may  be  made  in  a much  more  striking  manner,  over  mercu- 
ry, by  passing  into  ajar,  about  three  fourths  filled  with  this  gas,  a comparative- 
ly small  bulk  of  a solution  of  pure  potassa,  which  will  condense  the  whole  of  a 
large  quantity  of  the  gas.  If  dry  hydrate  of  potassa  be  substituted  in  this  ex- 
periment, no  change  will  ensue  ; which  proves  that  solution  is  essential  to  the 
action  of  alkalies  on  this  gas.  A solution  of  potassa,  which  has  condensed  all 
the  carbonic  acid  it  is  capable  of  absorbing,  when  evaporated  to  dryness,  af- 
fords carbonate  of  potassa.  H.  1.541. 

1476.  This  salt  is  fusible  without  decomposition,  at  a red  heat : 
it  is  very  soluble  in  water,  and  deliquesces  by  exposure  to  air, 
forming  a dense  solution,  once  called  oil  of  tartar  per  deliquium. 
Its  taste  is  alkaline,  and  it  renders  vegetable  blues  green. 

The  solution  of  carbonate  of  potassa  will  be  found  to  have  a 
much  milder  taste  than  the  pure  alkali,  and  no  longer  to  destroy  the 
texture  of  woollen  cloth  ; but  it  still  turns  to  green  the  blue  infusion 
of  vegetables. 

1477.  The  great  consumption  of  this  article  in  various  manufac- 
tures is  exclusively  supplied  by  the  combustion  of  vegetables,  and 
consequently  its  production  is  almost  limited  to  those  countries  which 
require  clearing  of  timber,  or  where  there  are  vast  natural  forests. 
The  English  market  is  chiefly  supplied  from  North  America.  If 
any  vegetable  growing  in  a soil  not  impregnated  with  sea-salt  be 
burned,  its  ashes  will  be  found  alkaline  from  the  presence  of  car- 
bonate of  potassa.  If  the  ashes  be  submitted  to  heat,  so  as  to  burn 
away  the  carbonaceous  matter  entirely,  they  become  a white  mass 
generally  termed  pearl-ash .* 

1478.  Bi-carbonate  of  Potassa , K0-)-2C02,  47.15  1 eq.  base  + 
44.24  2 eq.  acid  = 91.39  eq.  ; in  crystals  with  9 or  1 eq.  water  = 
100.39.  This  salt  is  formed  by  passing  a current  of  C into  a solu- 
tion of  the  carbonate  ; or  by  evaporatings  mixture  of  the  carbonates 
of  ammonia  and  potassa,  the  ammonia  being  dissipated  in  a pure 
state.  By  slow  evaporation,  the  bicarbonate  is  deposited  from  the 
liquid  in  hydrated  prisms  with  eight  sides,  terminated  with  dihedral 
summits. 

1479.  This  salt  is  milder  than  the  carbonate.  It  does  not  deli- 
quesce on  exposure.  It  requires  4 times  its  weight  of  water  at  60° 
for  solution.  At  a low  red  heat  it  is  converted  into  the  carbonate. 

14S0.  Carbonate  of  Soda , NaO+CO2  31.3  1 eq.  base  + 22.12  1 
eq.  acid  = 53.42  eq. ; in  crystals  with  90  or  10  eq.  water  =143.42, 
with  63  or  7 eq.  water  = 116.42  eq.,  is  chiefly  obtained  by  the  com- 
bustion of  marine  plants,  the  ashes  of  which  afford,  by  lixiviation,  the 
impure  alkali  called  soda.  Two  kinds  of  rough  soda  occur  in  the 
market : barilla  and  kelp  ; besides  which,  some  native  carbonate  of 
soda  is  also  imported.  Barilla  is  the  semifused  ash  of  the  salsola 


* For  ascertaining 
the  quantity  of  real 

(510.) 


the  value  of  different  samples  of  pearlash,  that  is  to  determine 
carbonate  of  potassa  in  a given  weight  of  impure  carbonate,  see 


349 


Carbonate  of  Ammonia. 

soda,  which  is  largely  cultivated  upon  the  Mediterranean  shore  Sect. i. 
of  Spain,  in  the  vicinity  of  Alicant.  Kelp  consists  of  the  ashes  of 
sea-weeds,  which  are  collected  upon  the  sea  coast  and  burned  in 
kilns,  or  merely  in  excavations  made  in  the  ground  and  surrounded 
by  stones.  It  seldom  contains  more  than  5 per  cent,  of  carbonated 
alkali,  and  about  24  tons  of  sea-weed  are  required  to  produce  one  ton 
of  kelp.  The  best  produce  is  from  the  hardest  fuel,  such  as  the 
serraius , digitatus,  nodosas , and  vesicnlosus  * * * § The  rough  alkali  is 
contaminated  by  common  salt,  and  impurities,  from  which  it  may  be 
separated  by  solution  in  a small  portion  of  water,  filtrating  the  solu- 
tion, and  evaporating  it  at  a low  heat  ; the  common  salt  may  be 
skimmed  off  as  its  crystals  form  upon  the  surface. t 

1481.  It  crystallizes  in  rhombic  octohedrons,  the  acute  angles  ge-  Crystals, 
nerally  truncated.  The  crystals  effloresce,  and  when  heated  dissolve 

in  their  water  of  crystallization.  By  continued  heat  they  are  ren- 
dered anhydrous  without  loss  of  carbonic  acid.  They  dissolve  in  s°lubility. 
about  two  parts  of  cold,  and  rather  less  than  their  weight  of  boiling 
water;  the  solution  being  alkaline.  The  crystals  usually  contain 
10  eq.  of  water. t 

1482.  Bicarbonate  of  Soda.  Na0-|-2C02,  31.3  1 eq.  base  -f-  Bicarbon- 
44.24  2 eq.  acid  = 75.54  ; in  crystals  with  9 or  1 eq.  water  ==  ate- 
84.54  eq.  This  salt  is  made  by  the  same  processes  as  bicarbonate 

of  potassa,  and  is  deposited  in  hydrated  crystalline  grains  by  evapo- 
ration. It  is  milder  than  the  carbonate  and  less  soluble,  requiring 
about  ten  times  its  weight  of  water  at  60°  for  solution.  It  is  con- 
verted into  the  carbonate  by  a red  heat. 

1483.  Sesquicarbonate , 2NaO.  3C02-f-4H0,  occurs  native  in  Afri-  Sesquicar- 

ca,  on  the  banks  of  soda  lakes,  and  is  called  Trona .§  bonate. 

1484.  Carbonate  of  Ammonia.  H3N-f-C,  17.15  1 eq.  base  -f- 

22.12  1 eq.  acid  — 39.27  eq.  The  only  method  of  obtaining  the  Carbonate 
substance  so  called  is  by  mixing  perfectly  dry  C and  NH3.  In  what-  nja. 

* McCulloch’s  Western  Islands , i.  122. 

+ The  crystals  of  soda-carb.  as  well  as  the  soda-ash  of  G.  B.  are  made  by  the  de- 
composition of  sea-salt ; for  a description  of  the  process  see  lire’s  Diet.  Arts  and  Man. 

1151. 

t The  purity  of  barilla  or  other  carbonates  of  soda,  may  be  ascertained  by  the  alka- 
limeter  (510).  In  the  analysis  of  barilla  and  kelp,  to  ascertain  the  relative  proportion 
of  soda,  it  may  be  useful  to  know  that  100  parts  of  dilute  nitric  acid,  specific  gravity 
1.36,  will  saturate  50  parts  of  dry  carbonate  of  soda,  which  are  equivalent  to  about 
29  of  pure  soda. 

§ Phillips  in  Jour.  Sci.  vii. 

Soda  water  is  a solution  of  soda  highly  charged  with  carbonic  acid  gas,  whereby  it  soda  water, 
acquires  a sparkling  appearance,  and  agreeable  pungent  taste,  and  certain  medicinal 
powers.  For  a plan  and  description  of  the  apparatus  see  Ure’s  Diet.  Arts  and  Man. 

1156. 

To  make  seltzer  water,  for  each  12  lbs.  Troy  take  55  grs.  carb.  soda,  17  carb.  lime,  Seltzer  water. 
18  carb.  magnesia,  3^  subphosphate  alumina,  3 chloride  potassium,  155  chlor.  sodium, 
and  3 of  finely  precipitated  silica,  this  solutionis  charged  with  353  cubic  inches  of 
carb.  acid  gas.  Ibid , 1155. 

The  disinfecting  soda  liquid  of  Labarraque  is  prepared  by  the  following  process,  i.abarraque’a 
Dissolve  2800  grains  of  crystallized  carbonate  of  soda  in  1.28  pints  of  water,  having  liquid, 
placed  the  solution  in  a Woulfe’s  apparatus,  pass  through  it  a current  of  chlorine  gas 
evolved  from  a mixture  of  957  grains  of  salt,  and  750  of  oxide  of  manganese,  acted 
upon  by  967  grains  of  oil  of  vitriol  previously  diluted  with  750  grains  of  water.  The 
operation  should  be  conducted  slowly. 

For  most  purposes  the  common  bleaching 'powder  sprinkled  about  or  dissolved  in 
water  is  quite  as  effectual  and  more  economical,  but  for  medical  uses  the  preparation 
should  be  more  nicely  attended  to.  See  Quart.  Jour,  of  Sci.,  &c.  N.  S.  i-  236— ii. 

460 — iii.  84  ; and  Amer.  Jour.  &c.  xiv.  251. 


350 


Salts — Carbonates. 


ChaP- v-  ever  proportion  the  two  gases  be  mixed,  they  unite  only  in  the  ratio 
of  1 vol.  of  the  former  to  2 of  the  latter,  and  condense  into  a white 
powder.  It  is  decomposed  by  water  into  ammonia  and  the  sesqui- 
carbonate. 

Bicarbon-  1485.  Bicarbonate  of  Oxide  of  Ammonium  is  formed  by  trans- 

arnmonf-,de  miuing  a current  of  C through  a solution  of  the  common  carbonate 
um.  of  ammonia.  On  evaporating  the  liquid  by  a gentle  heat,  the  bicar- 
bonate is  deposited  in  small  prisms  of  the  right  rhombic  system  ? 
having  no  smell,  and  very  little  taste.  It  contains  twice  as  much  C 
as  the  carbonate.  It  cannot  exist  without  the  presence  of  water,  of 
which  it  contains  22.7  percent.,*  or  2 eq.  It  may  therefore  be  con- 
sidered as  carbonate  of  basic  water  and  carbonate  of  oxide  of  ammo- 
nium, or  H0.C02+H4N0.C02. 

Sesqui-  1486.  Sesquicarbonate  of  Oxide  of  Ammonium.  The  common 
of oxide^f  car^onate  ammonia  of  the  shops,  Sub-carbonas  Ammonia  of  the 
ammom-0  Pharmacop.,  is  different  from  both  these  compounds.  It  is  prepared 
um.  by  heating  a mixture  of  one  part  of  hydrochlorate  of  ammonia  with 

one  part  and  a half  of  carbonate  of  lime,  carefully  dried.  Double 
decomposition  ensues  during  the  process  ; chloride  of  calcium  re- 
mains in  the  retort,  and  hydrated  sesquicarbonate  of  ammonia  is 
sublimed.  The  carbonic  acid  and  ammonia  are,  indeed,  in  proper 
proportion  in  the  mixture  for  forming  the  real  carbonate  : but,  owing 
to  the  presence  of  water,  generated  by  the  combination  of  the  oxygen 
of  the  lime  with  the  hydrogen  of  the  hydrochloric  acid,  part  of  the 
ammonia  is  disengaged  in  a free  state. 

1487.  The  salt  thus  formed  consists  of  34.3  parts  or  2 eq  of  am- 
monia, 66.36  parts  or  3 eq.  of  carbonic  acid,  and  18  parts  or  2 eq.  of 
water.  It  is,  therefore,  anhydrous  sesquicarbonate  of  oxide  of  am- 
monium, or  2H4NO-f~3CO\  When  recently  prepared,  it  is  hard, 
compact,  translucent,  of  a crystalline  texture,  and  pungent  ammoni- 
acal  odour;  but  if  exposed  to  the  air,  it  loses  weight  rapidly  from 
the  escape  of  pure  ammonia,  and  becomes  an  opaque  brittle  mass, 
which  is  the  bicarbonate. 

Carbonate  1488.  Carbonate  of  Baryta,  BaO-j-CO7,  76.7  1 eq.  base  + 22.12 
of  baryta.  1 eq.  acid  = 98.82  eq.,  occurs  abundantly  in  the  lead  mines  of  the 
north  of  England,  where  it  was  discovered  by  Withering,  and  has 
hence  received  the  name  of  I Vitherite.  It  may  be  prepared  by  way 
of  double  decomposition,  by  mixing  a soluble  salt  of  baryta  with  any 
of  the  alkaline  carbonates  or  bicarbonates.  It  is  anhydrous,  exceed- 
ingly insoluble  in  distilled  water,  requiring  4300  times  its  weight  of 
water  at  60°,  and  2300  of  boiling  water  for  solution  ; but  when  re- 
cently precipitated,  it  is  dissolved  much  more  freely  by  a solution  of 
carbonic  acid.  It  is  higly  poisonous. 

Carbonate  1489.  Carbonate  of  Strontia,  SrO-f-CO',  5I.S  1 eq.  base-)-  22.12 
of  strontia.  1 eq.  acid  = 73.92  eq.,  occurs  native  at  Strontian  in  Argyleshire, 
and  is  known  by  the  name  of  Strontianite ; it  may  be  prepared  in  the 
same  manner  as  carbonate  of  baryta.  It  is  anhydrous,  and  very  inso- 
luble in  pure  water,  but  is  dissolved  by  an  excess  of  carbonic  acid. 
Carbonate  1490.  Carbonate  of  Lime.  CaO-f-CO2,  28.5  1 eq.  base  + 22.12, 
of  lime.  ac-j  __  50  00  eqt  This  salt  is  a very  abundant  natural  production 


* Berzelius. 


351 


Carbonate  of  Magnesia . 

and  occurs  under  a great  variety  of  forms,  such  as  common  limestone,  Sect,  i. 
chalk,  marble,  and  Iceland,  spar,  and  in  regular  anhydrous  crystals, 
the  density  of  which  is  2.7.  Though  sparingly  soluble  in  pure 
water,  it  is  dissolved  by  carbonic  acid  in  excess  ; and  hence  the 
spring-water  of  limestone  districts  always  contains  carbonate  of  lime, 
which  is  deposited  when  the  water  is  boiled. 

1491.  Lime  has  a strong  attraction  for  carbonic  acid,  but  not  when  Carbonate, 
perfectly  dry  ; for  if  a piece  of  dry  quicklime  be  passed  into  a jar  of 
carbonic  acid  gas  over  mercury,  no  absorption  whatever  ensues. 

But  if  a bottle,  filled  with  carb.  acid  gas,  be  inverted  over  a mixture  of  lime  and  gXp. 
water  of  the  consistence  of  cream,  a rapid  absorption  will  be  observed,  especially 
if  the  bottle  be  agitated  ; or  if  a jar  or  bottle,  filled  with  carbonic  acid,  be  brought 
over  a vessel  of  lime  water,  on  agitating  the  vessel,  a rapid  diminution  will  ensue, 
and  the  lime  water  will  become  milky. 

1492.  When  a shallow  vessel  of  lime  water  is  exposed  to  the  Action  of 
air,  a white  crust  forms  on  the  surface,  and  this,  if  broken,  falls  to  air- 

the  bottom,  and  is  succeeded  by  another  till  the  whole  of  the  lime  is 
precipitated  from  the  solution.  This  is  owing  to  the  absorption  of 
carbonic  acid  gas  from  the  air  by  the  lime,  which  is  thus  rendered 
insoluble  in  water.  Dry  lime,  also,  when  exposed  to  the  atmosphere, 
first  acquires  moisture,  and  having  become  a hydrate,  next  absorbs 
carbonic  acid.  In  a sufficient  space  of  time,  all  the  characters  dis- 
tinguishing it  as  lime  disappear,  and  it  acquires  the  property  of 
effervescing  with  acids.  The  strong  affinity  of  lime  for  carbonic  acid 
enables  it  to  take  this  acid  from  other  substances.  Thus  carbonates 
of  alkalies  are  decomposed  by  lime.  h.  i.  58 7. 

1493.  The  carbonic  acid  existing  in  carbonate  of  lime  is  expelled  Carbonic 

by  a strong  red  heat.  If  distilled  in  an  earthen  retort,  carbonic  acid  1 exPel; 

gas  is  obtained,  and  lime  remains  in  the  retort  in  a pure  or  caustic 

state.  By  this  process  carbonate  of  lime  loses  about  45  per  cent. 

1494.  Carbonate  of  Magnesia.  MgO-|-C02,  20.7  1 eq.  base  -j-  Carbonate 
22.12  1 eq.  acid  ==  42.82  eq.  ; in  crystals,  with  27  or  3 eq.  water  = °f  ma§>ne' 
69.82.  It  is  met  with  occasionally  in  rhombohedral  crystals,  and  in 

a pulverulent  earthy  state,  but  more  commonly  as  a compact  mineral 
of  an  earthy  fracture  called  magnesite.  It  is  abundant  in  the  East 
Indies,  of  a snow-white  colour,  of  density  2.56,  and  so  hard  that  it 
strikes  fire  with  steel.*  It  is  obtained  in  minute  transparent  hexa- 
gonal prisms  with  three  eq.  of  water,  when  a solution  of  bicarbonate 
of  magnesia  evaporates  spontaneously  in  an  open  vessel.  The  crys- 
tals lose  their  water  and  become  opaque  by  a very  gentle  heat,  and 
even  in  a dry  air  at  60°.  By  cold  water  they  are  decomposed, 
yielding  a soluble  bicarbonate,  and  an  insoluble  white  compound 
of  hydrate  and  carbonate  of  magnesia ; and  hot  water  produces  the 
same  change  with  disengagement  of  carbonic  acid,  without  dissolv- 
ing any  magnesia.! 

1495.  When  carbonate  of  potassa  is  added  in  excess  to  a hot  solu- 
tion of  sulphate  of  magnesia,  a white  precipitate  falls,  which  after 
being  well  washed  has  been  long  considered  as  pure  carbonate  of 
magnesia  ; but  Berzelius  has  shown  that  it  consists  of  the  following 
ingredients  : — 


* Ann.  of  Philos,  xvii.  252. 


t Berzelius. 


352 


Salts — Carbonates. 


Chap.  V. 


Magnesia 
Carbonic  acid 
Water 


44.75 

35.77 

19.48 


82.8  or  4 eq. 
CG.36  or  3 eq. 
3(i  or  4 eq. 


Probable  formula  is 
M gO  .4  Ii  0-(-3Mg0C02 


100.00  185.16  or  1 eq. 

This  compound  is  said  to  require  2493  parts  of  cold,  and  9000  of 
hot  water  for  solution.  It  is  freely  dissolved  by  a solution  of  carbo- 
nic acid,  bicarbonate  of  magnesia  being  generated  ; but  on  allowing 
the  solution  to  evaporate  spontaneously,  carbonic  acid  is  given  off, 
and  crystals  of  the  hydrated  carbonate  above  mentioned  are  ob- 
tained. 

Carbonate  1496.  Carbonate  of  Protoxide  of  Iron.  FeO-fCO2,  36  1 eq.  base 
of  iron°Xi(le  H“  22.12  1 eq.  acid  = 58.12  eq.  Carbonic  acid,  with  the  protoxide 
of  iron,  constitutes  a salt  which  is  an  abundant  natural  production, 
occurring  sometimes  massive,  and  at  other  times  crystallized  in 
rhombohedrons.  This  protocarbonate  is  contained  also  in  most  of 
the  chalybeate  mineral  waters,  being  held  in  solution  by  free  carbo- 
nic acid  ; and  it  may  be  formed  by  mixing  an  alkaline  carbonate 
with  the  sulphate  of  protoxide  of  iron.  When  prepared  by  precipi- 
tation it  attracts  oxygen  rapidly  from  the  atmosphere,  and  the  pro- 
toxide of  iron,  passing  into  the  state  of  sesquioxide,  parts  with 
carbonic  acid.  For  this  reason,  the  carbonate  of  iron  of  the  Phar- 
macop.  is  of  a red  colour,  and  consists  chiefly  of  the  sesquioxide. 
Dicarbon  1497.  Dicarbonate  of  Protoxide  of  Copper.  2CuO-f-CO‘2,  79.2  2 
ate  of  pro-  eq.  base  -f-  22.12  1 eq.  acid  = 101.32  eq.*  It  occurs  as  a hydrate 
copper beautiful  green  mineral  called  malachite ; and  the  same  com- 
pound, as  a green  powder,  the  mineral  green  of  painters,  may  be 
obtained  by  precipitation  from  a hot  solution  of  sulphate  of  protoxide 
of  copper,  by  carbonate  of  soda  or  potassa.  When  obtained  from  a 
cold  solution,  it  falls  as  a bulky  hydrate  of  a greenish-blue  colour, 
which  contains  more  water  than  the  green  precipitate.  By  careful 
drying  its  water  may  be  expelled.  When  the  hydrate  is  boiled  for 
a long  time  in  water,  it  loses  both  carbonic  acid  and  combined  water, 
and  the  colour  changes  to  brown.  The  rust  of  copper,  prepared  by 
exposing  metallic  copper  to  air  and  moisture,  is  a hydrated  di- 
carbonate. 

The  blue  pigment  called  verditer,  prepared  by  decomposing  ni- 
trate of  protoxide  of  copper  with  chalk,  has  a similar  composition. t 
149S.  Carbonate  of  Protoxide  of  Lead.  111.6  1 eq.  base  -|- 
22.12  I eq.  acid  = 133.72  eq.  This  salt,  which  is  the  white  lead 
or  ceruse  of  painters,  occurs  native  in  white  prismatic  crystals  de- 
rived from  a right  rhombic  prism,  the  sp.  gr.  of  which  is  6.72.  It  is 
obtained  as  a white  pulverulent  precipitate  by  mixing  solutions  of  an 
alkaline  carbonate  with  acetate  of  protoxide  of  lead  ; and  it  is  pre- 
pared as  an  article  of  commerce  from  the  subacetate  by  a current  of 


Carbon- 
ate of  pro 
toxide  of 
lead. 


* In  Malachite  with  9 or  i eq  water  eq.  110.32. 

Refiner’,  rerdi-  + There  is  a fine  blue  cupreous  preparation,  called  Refiner's  Verditer,  principally  made 
ter.  by  silver  refiners.  It  consists,  according  to  Phillips,  of  three  proportionals  of  oxide, 

fourof  carbonic  acid,  and  two  of  water.  (Quart.  Jour,  of  Sci.  iv.  277.) 

According  to  Pelletier,  a good  verditer  may  he  obtained  as  follows  : add  a sufficient 
quantity  of  lime  to  nitrate  ot  copper  to  throw  down  the  oxide  ; it  gives  a greenish  pre- 
cipitate'that  is  to  be  washed  and  nearly  dried  upon  a strainer;  then  incorporate  it  with 
from  eight  to  ten  per  cent,  of  fresh  lime,  which  will  give  it  a blue  colour,  and  dry  it 
carefullv.  For  processes  see  Ure^s  Dtct.  Arts,  and  Man.  1274. 


353 


Hydrochlorate  of  Ammonia . 

carbonic  acid ; by  exposing  metallic  lead  in  minute  division  to  air  Sect,  n. 
and  moisture  ; and  by  the  action  on  thin  sheets  of  lead  of  the  va- 
pour of  vinegar,  by  which  the  metal  is  both  oxidized  and  converted 
into  a carbonate. 

1499.  Double  Carbonates.  One  of  the  most  remarkable  of  these  Double  car- 
is  the  double  carbonate  of  lime  and  magnesia,*  which  constitutes  the  bonates- 
minerals  called  bitter-spar,  pearl-spar,  and  Dolomite.  The  two  for- 
mer occur  in  rhombohedrons  of  nearly  the  same  dimensions  as  car- 
bonate of  lime.  Some  specimens  consist  of  the  two  carbonates  in  the 
ratio  of  their  equivalents;  but  this  ratio  is  very  variable,  since  iso- 
morphous  substances  crystallize  together  in  all  proportions,  t.  & L.  706. 


Section  II.  Ordered.  Hydro- Salts. 

This  section  includes  those  salts,  the  acid  or  base  of  which  con-  Hydro- 
tains  hydrogen.  The  salts  formerly  called  muriates  or  hydrochlorates  salts* 
of  metallic  oxides,  have  been  already  described  as  chlorides  of  metals ; 
as  also  those  of  hydriodic  and  other  hydracids;  the  neutralizing 
power  of  the  acids  being  considered  as  due  to  the  direct  union  of  the 
chlorine,  iodine,  &c.,  with  the  metal  itself.  Some  of  these  com- 
pounds may  be  more  properly  placed  in  the  fourth  section,  as  in 
them  the  hydracid  acts  rather  as  a base  or  electro-positive  ingredient, 
than  as  an  acid  or  electro-negative  substance.! 

1500.  The  compounds  of  ammonia  with  the  hydracids  may  be  Ammoni- 

described  as  chlorides  of  the  hypothetical  radical  ammonium.  aca  sa  ts' 

1501.  Ammoniacal  Salts  are  recognized  by  the  addition  of  pure 
potassa  or  lime,  when  the  odour  of  ammonia  may  be  perceived. 

Those  which  contain  a volatile  acid  may  in  general  be  sublimed 
without  decomposition ; but  the  ammonia  is  expelled  by  heat  from 
those  acids  which  are  much  more  fixed  than  itself. 

1502.  Hydrochlorate  of  Ammonia , H3N-f-HCl,  17.15  1 eq.  base  Hydrochlo- 
+ 36.42  1 eq.  acid  = 53.57.  This  salt,saZ  ammoniac  of  commerce,  rate  of  am- 
was  formerly  imported  from  Egypt,  where  it  is  procured  by  subli-  moma’ 
mation  from  the  soot  of  camel’s  dung;  but  it  is  now  manufactured 

by  several  processes.  The  most  usual  is  to  decompose  sulphate  of 
ammonia  by  the  chloride  either  of  sodium  or  magnesium,  when 
double  decomposition  ensues,  giving  rise  in  both  cases  to  hydro- 
chlorate of  ammonia,  and  to  sulphate  of  soda  when  chloride  of  so- 
dium is  used,  and  to  sulphate  of  magnesia  when  chloride  of  mag- 
nesium is  employed.  The  sal  ammoniac  is  afterwards  obtained  in 
a pure  state  by  sublimation.  The  method  now  generally  used  for 
obtaining  sulphate  of  oxide  of  ammonium  is  to  decompose  with 
sulphuric  acid  the  hydrosulphate  and  hydrocyanate  of  ammonia 
which  is  collected  in  the  manufacture  of  coal-gas;  but  it  may  also 
be  procured  either  by  lixiviating  the  soot  of  coal,  which  contains 
sulphate  of  oxide  of  ammonium  in  considerable  quantity,  or  by  di- 
gesting with  gypsum  impure  sesquicarbonate  of  oxide  of  ammonium, 
carbonate  of  ammonia,  procured  from  the  destructive  distillation 

*Mg0C02+Ca0C02.  50.62  1 eq-  carb.  lime  + 42.82  I eq.  carb.  mag.  — 93.44  eq. 

+ See  Kane’s  observations  in  Dublin  Jour,  of  Sci.  i.  265. 

45 


354 


Chap.  V. 


Properties. 


Native. 


Origin  of 
the  name. 


Formation 

illustrated. 


Uses, 


Hydroflu- 
ate  of  am- 
monia. 


Hydrosul- 
pbate  of 
ammonia. 


Salts — Hydro - Salts. 

of  bones  and  other  animal  substances,  so  as  to  form  an  insoluble 
carbonate  of  lime  and  a soluble  sulphate  of  oxide  of  ammonium. 

1503.  Hydrochlorate  of  ammonia  has  a pungent  saline  taste,  a 
density  of  1.45,  and  is  tough  and  difficult  to  be  pulverized.  It  is  so- 
luble in  alcohol  and  water,  requiring  for  solution  three  times  its 
weight  of  water  at  60°,  and  an  equal  weight  at  212°.  It  usually 
crystallizes  from  its  solution  in  feathery  crystals,  but  sometimes  in 
cubes  or  octohedrons.  At  a temperature  below  that  of  ignition  it 
sublimes  without  fusion  or  decomposition,  and  condenses  on  cool 
surfaces  as  anhydrous  salt,  which  absorbs  humidity  in  a damp  at- 
mosphere, but  is  not  deliquescent.  In  commerce  it  usually  occurs  as 
procured  by  sublimation,  in  white  cakes,  hard  and  somewhat  elastic. 

1504.  Native  Hydrochlorate  of  Ammonia , occurs  massive  and 
crystallized,  in  the  vicinity  of  volcanoes,  and  in  the  cracks  and  pores 
of  lava,  near  their  craters.  An  efflorescence  of  native  sal  ammoniac  is 
sometimes  seen  upon  pit-coal.  Its  colour  varies  from  the  admixture 
of  foreign  matter,  and  it  is  frequently  yellow  from  the  presence  of 
sulphur.  It  is  said  that  considerable  quantities  of  native  sal-ammo- 
niac are  also  found  in  the  country  of  Bucharia,  where  it  occurs  with 
sulphur  in  rocks  of  indurated  clay.  The  ancients,  according  to 
Pliny,  called  this  salt  ammoniac , because  it  was  found  near  the  tem- 
ple of  Jupiter  Ammon,  in  Africa. 

1505.  This  salt  may  be  produced  di- 
rectly by  means  of  the  apparatus  (Fig. 

186.)  Into  one  of  the  retorts  a small 
quantity  of  hydrochloric  acid  or  the 
materials  from  which  the  acid  gas  is 
usually  obtained  (628,)  is  introduced  ; 
and  into  the  other  liquid  ammonia  (or 
the  mixture  of  lime  and  hydrochlo- 
rate of  ammonia  (729.)  The  evolved 
gases  passing  into  the  globe  unite 
producing  dense  clouds  of  hydrochlorate  of  ammonia  which  concrete  upon  the 
inner  surface. 

We  may  also  form  it  by  mixing  over  mercury,  equal  measures  of  ammoniacal 
gas,  and  hydrochloric  acid  gas,  which  are  entirely  condensed  into  a white  solid. 

1506.  Sal-ammoniac  is  used  in  the  arts  for  a variety  of  purposes, 
especially  in  certain  metallurgic  operations.  It  is  used  in  tinning, 
to  prevent  the  oxidation  of  the  surface  of  copper ; and  small  quan- 
tities are  used  by  dyers.  Dissolved  in  nitric  acid,  it  forms  the  aqua 
regia  of  commerce,  used  for  dissolving  gold,  instead  of  a mixture  of 
nitric  and  hydrochloric  acids  (637.)* 

1507.  Hydrofluate  of  Ammonia , H3N-|-HF,  36.83  eq.  It  is  pre- 
pared by  mixing  1 part  of  sal  ammoniac  with  2i  of  fluoride  of  so- 
dium, both  dry  and  in  fine  powder,  gently  heating  the  mixture  in 
a platinum  vessel,  and  receiving  the  sublimed  salt  in  a second  pla- 
tinum vessel,  the  temperature  of  which  is  not  allowed  to  exceed 
212°. 

1505.  Hydrosulphate  of  Ammonia . H3N-|-HS,  17.15  1 eq.  base 
— |—  17. 1 1 eq.  acid  = 34.25.  This  salt,  also  called  hydrosulphuret 
of  ammonia,  and  formerly  the  fuming  liquor  of  Boyle , is  prepared 
by  heating  a mixture  of  one  part  of  sulphur,  two  of  sal  ammoniac, 


* Hydriodate,  H3N+HI,  17.15  base  + 127.3  1 eq.  acid  = 144.45  eq.,  and  Hydro- 
bromate  of  amvionia,  may  be  formed  by  similar  processes. 


Fig.  186. 


Sulphur- Salts . 


355 


and  two  of  unslaked  lime.  The  volatile  products  are  ammonia  and 
hydrosulphate  of  ammonia  ; and  the  fixed  residue  consists  of  sul- 
phate of  lime  with  chloride  and  sulphuret  of  calcium.  The  hy- 
drosulphuric acid  is  formed  from  the  hydrogen  of  hydrochloric  acid 
uniting  with  sulphur,  and  the  oxygen  of  the  sulphuric  acid  is  de- 
rived from  decomposed  lime,  the  calcium  of  which  is  divided  be- 
tween the  chlorine  of  the  hydrochloric  acid  and  the  sulphur.  Hy- 
drosulphate of  ammonia  may  also  be  formed  by  the  direct  union  of 
its  constituent  gases,  and  if  they  are  mixed  in  a glass  globe  kept 
cool  by  ice,  the  salt  is  deposited  in  crystals.  It  is  much  used  as  a 
reagent,  and  for  this  purpose  is  usually  prepared  by  saturating  a so- 
lution of  ammonia  with  hydrosulphuric  acid  gas.^' 

1509.  Salts  of  Phosphuretted  Hydrogen.  Phosphu retted  hydro- 
gen is  a feeble  alkaline  base,  which  combines  with  some  of  the  hy- 
dracids. 

The  salt  best  known  is  the  hydriodate  of  phosphuretted  hydrogen, 
first  noticed  by  Gay-Lussac,  which  is  formed  of  127.3  parts  or  1 eq. 
of  acid  and  34.4  parts  or  1 eq.  of  base,  and  crystallizes  in  cubes. 


Sect.  III. 


Use. 


Section  III.  Order  3 d.  Sulphur- Salts. 


The  compounds  described  in  this  section  are  double  sulphurets,  Sulphur* 
just  as  the  oxy-salts  in  general  are  double  oxides.  Their  resem-  salts, 
blance  in  composition  to  salts  is  perfect.  The  principal  sulphur-ba- 
ses are  the  protosulphurets  of  potassium,  sodium,  lithium,  barium, 
strontium,  calcium,  and  magnesium,  and  hydrosulphate  of  ammo- 
nia ; and  the  principal  sulphur-acids  are  the  sulphurets  of  arsenic, 
antimony,  tungsten,  molybdenum,  tellurium,  tin,  and  gold,  together 
with  hydrosulphuric  acid,  bisulphuret  of  carbon,  and  sulphuret  of 
selenium.  The  sulphur-salts  with  two  metals  are  so  constituted, 
that  if  the  sulphur  in  each  were  replaced  by  an  equivalent  quantity 
of  oxygen,  an  oxy-salt  would  result.  The  analogy  between  oxy- 
salts  and  sulphur-salts  is  rendered  still  closer  by  the  circumstance 
that  hydrosulphuric  and  hydrosulphocyanic  acids  have  the  charac- 
teristic properties  of  acidity,  and  unite  both  with  ammonia  and  with 
sulphur-bases. 

The  sulphur-salts  may  be  divided  into  families,  characterized  by  Divjsjon  0f 


Fie.  187. 

* Fig.  187,  represents  the 
disposition  of  the  apparatus 
for  this  process  : a , a small 
furnace ; 6,  a tubulated  earth- 
ern  retort  containing  the  a- 
bove  materials  ; c,  an  adap- 
ting tube ; e,  a glass  balloon 
for  condensing  the  vapour; 

/ a receiver  ; g,  a bottle  of 
water,  into  which  the  glass 
tube,  issuing  from  the  upper 
part  of  the  receiver,  e,  is 
made  to  dip  about  half  an 
mch.  The  product  in  the 
bottle/,  may  be  mixed  with  the  water  mg-,  and  the  whole  used  for  washing  out  the 
receiver  e.  It  is  retained  in  the  pharmacopaeia,  and  may  be  extemporaneously  made 
by  passing  hydrosulphuric  acid  gas  from  an  oil  flask  with  a bent  tube  jinto  aqua  am- 
moniac kept  cold. 


sulphur- 

salts. 


356 


Salts — Sulphur-  Salts. 


Chap.  V. 


Hydro- 

sulphurets. 


Hydro-sul- 
phuret  of 
potassium. 


Process. 


Hydro-sul- 

Ehuret  of 
arium. 


Carbo- 

sulphurets. 

Carbo-sul- 
phuret  of 
potassium. 


containing  the  same  sulphur-acid.  For  the  purpose  of  indicating 
that  such  salts  are  double  sulphurets,  as  well  as  to  distinguish  them 
readily  from  other  kinds  of  salts,  the  generic  name  of  each  family 
may  be  constructed  from  the  sulphur-acid  terminated  with  sulphuret. 
Thus  the  salts  which  contain  persulphuret  of  arsenic  or  hydrosul- 
phuric  acid  as  the  sulphur-acid  are  termed  arsenio-sulphurets  and 
hydro-sulphurets ; and  a salt  composed  of  each  of  these  sulphur- 
acids  with  sulphuret  of  potassium  is  termed  arsenio-sulphuret  and 
hydro-sulphuret  of  sulphuret  of  potassium.  For  the  sake  of  brevity 
the  metal  of  the  base  may  alone  be  expressed,  it  being  understood 
that  the  positive  metal  in  a sulphur-salt  enters  as  a protosulphuret 
into  the  compound. 

1510.  Hydro- Sulphurets.  The  sulphur-salts  contained  in  this 
group  have  hydro-sulphuric  acid  for  their  electro-negative  ingredient. 
Most  of  them  which  have  been  studied  are  soluble  in  water,  and 
may  be  obtained  in  crystals  by  evaporation.  They  are  decomposed 
by  exposure  to  the  air,  yielding  at  first  bisulphurets  of  the  metal, 
and  then  a hyposulphite.  By  acids  the  hydrosulphuric  acid  is  ex- 
pelled with  effervescence. 

1511.  Hydro-sulphuret  of  Potassium , KS-f-HS,  55.25  1 eq.  sul- 
phur-base -f-  17.1  1 eq.  sulphur  acid  = 72.35  eq.  This  salt  is  ob- 
tained in  the  anhydrous  state  by  introducing  anhydrous  carbonate 
of  potassa  into  a tubulated  retort,  transmitting  through  it  a current 
of  hydrosulphuric  acid  gas,  and  heating  the  salt  to  low  redness. 

The  same  salt  is  prepared  in  the  moist  way  by  introducing  a solution  of  pure 
potassa,  free  from  carbonic  acid,  into  a tubulated  retort,  expelling  atmospheric 
air  by  a current  of  hydrogen  gas,  and  then  saturating  the  solution  with  hydro- 
sulphuric acid.  At  nrst  the  potassa,  as  in  the  former  process,  interchanges  ele- 
ments with  the  gas,  yielding  water  and  protosulphuret  of  potassium ; after 
which  the  protosulphuret  unites  with  hydrosulphuric  acid.  The  solution 
should  be  evaporated  in  the  retort  to  the  consistence  of  syrup,  a current  of  hy- 
drogen gas  being  transmitted  through  the  apparatus  the  whole  time ; and  on 
cooling  the  salt  crystallizes  in  large  four  or  six  sided  prisms,  which  are  colour- 
less if  air  was  perfectly  excluded. 

1512.  Hydrosulphuret  of  Barium , BaS-|-HS,  84.8  1 eq.  sulphur 
base,  -(-17.1  acid  = 101.9  eq.  It  is  prepared  by  the  action  of 
hydrosulphuric  acid  on  a solution  of  baryta  with  the  precautions  al- 
ready mentioned  for  excluding  atmospheric  air,  and  crystallizes  by 
evaporation  in  four-sided  prisms,  which  are  very  soluble  in  water.* 

1513.  Car  bo-sulphur  ets.  The  acid  of  these  sulphur-salts  is  bi- 
sulphuret  of  carbon. 

1514.  Carbo-sulphuret  of  Potassium , KS-f-CS5,  55.25  sulphur  -f- 
38.32  sulphur  acid  = 93.57  eq.  On  agitating  bisulphuret  of  car- 
bon with  a strong  alcoholic  solution  of  protosulphuret  of  potassium, 
the  liquid  when  set  at  rest  separates  into  three  layers,  the  lowest  of 
which  is  carbo-sulphuret  of  potassium,  and  is  of  the  consistence  of 
syrup.  Another  process  is  to  digest  bisulphuret  of  carbon  at  86° 
in  a corked  bottle  full  of  a strong  aqueous  solution  of  proto- 
sulphuret of  potassium,  until  the  latter  is  saturated.  A concen- 
trated solution  of  this  salt  is  of  a deep  orange,  almost  red  colour; 


* For  other  hydrosulphurets  and  carbo-sulphurets  see  Turner  and  Liebig’s  Elem. 
713. 


Molybdo-  Sulphur  ets.  357 

and  when  evaporated  at  86°  to  the  consistence  of  syrup,  a deliques-  Sect- hi. 
cent  yellow  crystalline  salt  is  deposited,  which  is  sparingly  soluble 
in  alcohol. 

1515.  Carbo- sulphur  et  of  Hydro  sulphate  of  Ammonia , (H3N-|-  Carbo-sul- 
HS)  + CS2,  34.25  1 eq.  sulphur  + 38.32  1 eq.  sulphur  acid  = 

72.57  eq.  This  salt  is  prepared  by  filling  a bottle  with  10  mea-phateof 
sures  of  nearly  absolute  alcohol  saturated  with  ammoniacal  gas  and  ammonia. 

I measure  of  bisulphuret  of  carbon,  and  inserting  a tight  cork.  As  Process, 
soon  as  the  liquid  has  acquired  a yellowish  brown  colour,  the  bottle 
is  plunged  into  ice-cold  water,  when  the  carbo-sulphuret  is  deposited 
either  in  yellow  penniform  crystals  or  as  a crystalline  powder.  The 
whole  is  thrown  upon  a linen  filter,  and  the  salt  after  being  washed 
first  with  absolute  alcohol  and  then  with  ether,  is  dried  by  pressure 
within  folds  of  bibulous  paper. 

1516.  This  salt  is  very  volatile  and  can  only  be  preserved  in  well  Volatile, 
corked  bottles.  Exposed  to  the  air  it  absorbs  humidity  and  ac- 
quires a red  colour. 

1517.  Arsenio-sulphurets.  Berzelius  finds  that  each  of  the  three  Arsenio- 
sulphurets  of  arsenic  (page  276)  is  capable  of  acting  as  a sulphur-  sulphurets. 
acid,  giving  rise  to  three  distinct  families  of  sulphur-salts,  distin- 
guishable by  the  terms  ar senio -per sulphur et s , arscnio-sesquisulphur- 

ets , and  ar  senio -proto  sulphurets. 

1518.  Persulphuret  of  Arsenic , is  a very  powerful  sulphur-acid, 
violently  displacing  hydrosulphuric  acid  from  its  combinations  with 
sulphur-bases, even  at  common  temperatures ; and  when digested  with 
earthy  or  alkaline  carbonates,  it  expels  carbonic  acid.  The  salts 
of  this  sulphur-acid  may  be  prepared  by  several  methods.^ 

1519.  Most  of  the  arsenio-persulphurets  of  the  second  class  of  Characters, 
metals  are  insoluble  ; but  those  of  the  metals  of  the  alkalies  and  al- 
kaline earths  are  very  soluble  in  water,  have,  a lemon-yellow  colour 

in  the  anhydrous  state,  and  are  colourless  when  combined  with  water 
of  crystallization  or  in  solution.  When  exposed  to  heat  in  close 
vessels  they  give  off  sulphur,  and  an  arsenio-sesquisulphuret  is  gene- 
rated. In  the  solid  state  they  are  very  permanent  in  the  air,  and 
even  in  solution  oxidation  takes  place  with  great  slowness.  When 
decomposed  by  an  acid,  persulphuret  of  arsenic  subsides,  hydrosul- 
phuric acid  gas  escapes,  and  a salt  of  the  alkali  is  generated. 

The  salts  in  which  sesquisulphuret  of  arsenic  acts  as  an  acid,  re- 
semble those  of  the  persulphuret  both  in  their  general  characters  and 
mode  of  formation. 

1520.  Molybdo- Sulphurets.  The  electro-negative  ingredient  of Molybdo- 
these  salts  is  the  tersulphuret  of  molybdenum,  and  the  most  remark-  sulphurets. 
able  of  them  is  the  molybdo-sulphuret  of  potassium,  which  is  readily 
formed  by  decomposing  with  hydrosulphuric  acid  gas  a rather  strong 
solution  of  molybdate  of  potassa.  If  no  iron  is  present,  the  liquid 
acquires  a beautiful  red  colour,  like  the  solution  of  bichromate  of 
potassa,  and  on  evaporation  prismatic  crystals  with  four  and  eight 

sides  are  deposited.  Berzelius  describes  this  compound  as  one  of 
the  most  beautiful  which  chemistry  can  produce  ; the  crystals,  by 
transmitted  light,  are  ruby-red,  and  their  surfaces,  while  moist  with 


* For  which  see  Turner  and  Liebig’s  Elem.  715. 


358 


Chap.  V. 


Antimonio- 

sulphureta. 


Tunpto- 

sulphurets. 


Haloid 

salts. 


Hydrareo- 

chlorides. 


Auro  chlo- 
rides. 


Platino- 

chlorides. 


Palladio- 

chlorides. 


Sails — Haloid  Salts. 

the  solution  which  yielded  them,  shine  like  the  wings  of  certain 
insects  with  a metallic  lustre  of  a rich  green  tint.  The  crystals  are 
anhydrous,  dissolve  readily  in  water,  but  are  insoluble  in  alcohol. 
On  the  addition  of  sulphuric  or  any  of  the  stronger  acids,  a salt  of 
potassa  is  generated  with  escape  of  hydrosulphuric  acid,  and  preci- 
pitation of  tersulphuret  of  molybdenum. 

1521.  Antimonio- Sulphur ets.  When  two  parts  of  carbonate  of 
potassa  are  intimately  mixed  with  four  of  sesquisulphuret  of  antimo- 
ny and  one  part  of  sulphur,  and  the  mixture  is  fused,  an  antimonio- 
persulphuret  of  potassium  is  generated.  On  digesting  in  water,  a 
subantimonio-persulphuret  is  dissolved,  and  is  deposited  by  gentle 
evaporation  in  large  colourless  tetrahedrons,  which  become  yellow  on 
exposure  to  the  air. 

1522.  Tung sto- Sul phurcts.  The  best  known  of  these  salts  is  that  of 
potassium,  in  which  tersulphuret  of  tungsten  is  combined  with  pro- 
tosulphuret  of  potassium.  It  is  formed  when  a solution  of  tungstate 
of  potassa  is  decomposed  by  hydrosulphuric  acid,  and  crystallizes  by 
evaporation  in  flat  quadrilateral  prisms,  which  are  anhydrous,  and 
are  of  a pale  red  colour. 


Section  IV.  Order  4th.  Haloid  Salts. 

1523.  Under  this  order  are  included  substances  composed  like  the 
preceding  salts  of  two  bi-elementary  compounds,  one  or  both  of  which 
are  analogous  in  composition  to  sea-salt.  The  principal  groups 
consist  of  double  chlorides,  double  iodides,  and  double  fluorides.  In 
these  the  haloid  bases  belong  usually  to  the  electro-positive  metals, 
and  the  haloid  acids  to  the  metals  which  are  electro-negative.  The 
same  principles  of  nomenclature  are  applied  to  them  as  to  the  sul- 
phur salts. 

1524.  Hydrar go  chlorides.  The  haloid  acid  of  this  family  is 
bichloride  of  mercury,  which  reddens  litmus  paper,  and  loses  the 
property  when  a haloid  base  is  present,  thus  bearing  a close  analogy 
to  ordinary  acids.  They  are  obtained  by  mixing  the  ingredients  in 
the  ratio  for  combining,  and  setting  aside  the  solution  to  crystallize. 
The  ammoniacal  salt  has  long  been  known  under  the  name  of  salt 
of  alembroth. 

1525.  Auro-chlorides.  The  electro-negative  ingredient  of  these 
salts  is  the  terchloride  of  gold.  They  are  prepared  by  mixing  the 
chlorides  in  atomic  proportions  and  setting  aside  the  solution  to  crys- 
tallize. Most  of  them  have  an  orange  or  yellow  colour,  and  consist 
of  single  equivalents  of  their  constituent  chlorides. 

1526.  P latino-chlorides.  Both  the  protochloride  and  bichloride  of 
platinum  act  as  haloid  acids.  The  platino-protochloride  of  potassium 
is  made  by  mixing  chloride  of  potassium  with  a solution  of  proto- 
chloride of  platinum  in  hydrochloric  acid.  It  crystallizes  in  red,  an- 
hydrous' prisms  and  consists  of  single  equivalents  of  its  constitu- 
ent chlorides. 

1527.  The  Platino-bichloride  of  Hydrochlorate  of  Ammonia  falls 
as  a lemon-yellow  powder,  when  sal  ammoniac  is  mixed  with  a 
strong  solution  of  bichloride  of  platinum. 

1528.  Palladio-chlorides  are  those  in  which  the  chlorides  of  palla- 


Chlorides  with  Ammonia. 


359 


dium  act  as  haloid  acids,  combining  with  many  of  the  metallic  chlo-  Sect,  iv. 
rides,  when  their  respective  solutions  are  mixed  and  evaporated. 

1529.  Rhodio-chlorides  are  formed  when  sesquichloride  of  rho-  R^°dio- 
dium  combines  with  the  chlorides  of  potassium  and  sodium. 

The  chlorides  of  iridium  and  osmium  act  as  haloid  acids  and  pro- 
duce iridio-chlorides  and  osmio-chlorides. 

1530.  Oxy -chlorides.  Chemists  are  acquainted  with  a considera-  Oxy-chlo- 
ble  number  of  compounds  in  which  a metallic  oxide  is  united  with  rides. 

a chloride  either  of  the  same  metal,  which  is  the  most  frequent,  or 
of  some  other  metal.  These  compounds  are  commonly  termed  sub- 
muriate,s,  on  the  supposition  that  they  consist  of  hydrochloric  acid 
combined  with  two  or  more  eq.  of  an  oxide. 

1531.  Oxy -chlorides  of  Iron.  When  the  crystallized  protochloride  Oxy-chlo- 
of  iron  is  heated  without  exposure  to  the  air,  the  last  portions  of  its  Tjjjes  of 
water  exchange  elements  with  part  of  the  chloride  of  iron,  yielding 
hydrochloric  acid,  which  is  evolved,  and  protoxide  of  iron.  On 
raising  the  heat  so  as  to  expel  the  pure  chloride  of  iron,  a deep  green 
oxy-chloride  in  scaly  crystals  remains.* 

1532.  The  ochreous  matter  which  falls  when  a solution  of  the 
protochloride  of  iron  is  exposed  to  the  air,  is  hydrated  sesquioxide  of 
iron  combined  with  some  sesquichloride.  A similar  hydrate  is  ob- 
tained by  mixing  with  a solution  of  the  sesquichloride  of  iron  a 
quantity  of  alkali  insufficient  for  complete  decomposition.  When  a 
solution  of  the  sesquichloride  is  evaporated  to  dryness  without  expo- 
sure to  the  air,  the  last  portions  of  water  exchange  elements  with  the 
sesquichloride,  hydrochloric  acid  is  disengaged,  and  after  subliming 
the  pure  anhydrous  sesquichloride,  a compound  in  large,  brown, 
shining  laminas  is  left,  which  consists  of  sesquioxide  and  sesquichlo- 
ride of  iron.t 

1533.  Oxy-chloride  of  Copper  falls  as  a green  hydrate  when  po-  Oxy-chlo- 
tassa  is  added  to  a solution  of  chloride  of  copper  insufficient  for  its  rides  of 
complete  decomposition.  When  its  water  is  expelled  it  becomes  0f  coPPer' 

a liver-brown  colour.  According  to  Berzelius  it  consists  of  1 eq. 
chloride  and  3 eq.  oxide  of  copper. 

1534.  It  is  used  as  a pigment  under  the  name  of  Brunswick  green , Brunswick 
being  prepared  for  that  purpose  by  exposing  metallic  copper  to  hy-  Sreen- 
drochloric  acid  or  a solution  of  sal-ammoniac.  The  same  compound 

is  generated  during  the  corrosion  of  copper  in  sea-water. 

1535.  Oxy-chloride  of  Lead  is  prepared  by  adding  pure  ammonia  Oxy-chlo- 
to  a hot  solution  of  chloride  of  lead.  Another  is  known  under  the  j^of 
name  of  mineral  ox  patent  yellow,  and  is  prepared  by  the  action  of  patent 
moist  sea-salt  on  litharge,  by  which  means  portions  of  the  protoxide  iow. 
and  sea-salt  exchange  elements,  yielding  soda  and  chloride  of  lead. 

After  washing  away  the  alkali,  the  mixed  oxide  and  chloride  are 
dried  and  fused. 

1536.  Chlorides  with  Ammonia.  The  perchlorides  of  tin  and  a Chlorides 
few  other  metals  absorb  ammonia  at  common  temperatures,  and  most  with  am- 
of  the  other  chlorides  absorb  it  when  gently  warmed.  Calomel moma* 
absorbs  half  an  equiv.  and  forms  a black  compound,  but  on  exposure 

to  the  air  the  ammonia  flies  off,  and  pure  white  calomel  remains. 


* Berzelitjs. 


t Ibid. 


360 


Salts — Oxy-iodides. 


>huretted 

lydrogen. 


Double  io- 
dides. 


Chap  v.  Corrosive  sublimate,  by  the  aid  of  heat,  rapidly  absorbs  half  an  eq. 
and  forms  a white  compound  which  is  insoluble  in  water,  and  bears 
a considerable  temperature  without  decomposition  ; the  white  preci- 
pitate of  pharmacy  is  probably  analogous  in  nature,  though  the  ratio 
of  its  ingredients  is  different. 

1537.  Most  of  these  compounds  lose  their  ammonia  by  mere  ex- 
posure to  the  air,  and  it  is  expelled  from  nearly  all  of  them  by  a 
very  moderate  heat. 

Chlorides  1538.  Chlorides  ivith  phosphuretted  hydrogen.  Rose  has  traced  a 
with  pbos-  remarkable  analogy  between  ammonia  and  phosphuretted  hydrogen, 
especially  in  the  compounds  which  they  form  with  metallic  chlorides. 
The  phosphuretted  hydrogen  is  readily  displaced  by  water,  or  a so- 
lution of  ammonia,  from  the  compounds  of  phosphuretted  hydrogen 
and  the  perchlorides  of  tin,  titanium,  antimony,  iron,  and  alumina, 
all  of  which  correspond  to  ammoniacal  chlorides  of  similar  composi- 
tion. 

1539.  Double  Iodides.  These  compounds  have  not  yet  been 
closely  studied  ; but  there  is  no  doubt  that  the  iodides  are  capable  of 
forming  with  each  other  an  extensive  series  of  compounds.  A vari- 
ety of  double  iodides  have  been  described  by  Boullay,  and  among 
them  a compound  of  biniodide  of  mercury  and  hydriodic  acid.*  in 
general  the  double  hydrargo-biniodides  contain  single  equivalents  of 
the  respective  iodides.  Liebig  obtained  a compound  of  the  bichlo- 
ride and  biniodide  of  mercury,  consisting  of  two  eq.  of  the  former  to 
one  eq.  of  the  latter,  as  indicated  by  the  formula,  Hgl2-|-2HgCl2. 

Several  compounds  of  biniodide  of  platinum  with  other  iodides 
have  been  studied  by  Kane  and  Lassaigne.t 

1540.  Platino-biniodide  of  Potassium , is  prepared  by  digesting  an 
biniodide  of  excess  of  biniodide  of  platinum  in  a rather  concentrated  solution  of 
potassium,  iodide  of  potassium.  By  spontaneous  evaporation  it  crystallizes  in 

small  rectangular  plates  surmounted  sometimes  with  a four-sided 
pyramid,  which  are  anhydrous,  unchanged  in  the  air,  and  insoluble 
in  alcohol.  The  colour  of  the  crystals  is  black  with  a metallic  lustre, 
and  they  yield  a deep  claret-coloured  solution  with  water.  The 
biniodide  of  platinum  appears  to  combine  also  with  the  iodide  of  pla- 
tinum ; but  the  compound  has  only  been  obtained  in  solution. 

Platino-  1541.  Platino-biniodide  of  Hydrogen.  This  compound  consists 
bimodide  of  of  hydriodic  acid  and  biniodide  of  platinum,  in  which  the  former  is 


Platino- 


hydrogeu. 


Oxy-io- 

dides. 


regarded  as  the  electro-positive  element.  It  is  prepared  by  acting 
on  biniodide  of  platinum  with  a cold  dilute  solution  of  hydriodic 
acid,  which  gradually  acquires  a deep  claret  colour,  and  by  evapora- 
tion under  a bell-jar  with  quicklime,  deposits  black  acicular  crystals. 
The  crystals  become  moist  by  exposure  to  the  air. 

1542.  Oxy-iodides.  The  principal  oxy-iodides  at  present  known 
to  chemists  are  those  formed  by  the  oxide  and  iodide  of  lead.  When 
iodide  of  potassium  is  mixed  with  acetate  of  oxide  of  lead  in  excess, 
the  yellow  iodide  at  first  formed  combines  with  oxide  of  lead  and  ac- 
quires a white  colour  ; and  the  same  compound  is  obtained  directly 
by  employing  a subacetate.  Denot  finds  that  there  are  three  oxy- 


* Ann.  de  Chem.  et  de  Phys.  xxxiv. 

t Dublin  Jour,  of  Sci.  i.  304,  and  Ann.  de  Chim.  et  de  Phjys.  li.  125. 


Tit  ano  fluorides.  361 

iodides,  in  which  1 eq.  of  iodide  of  lead  is  united  with  one,  two,  and  Sect,  iv. 
five  equivalents  of  oxide  of  lead. 

1543.  Double  Fluorides . The  researches  of  Berzelius  have  led  to  Double 
the  formation  of  several  extensive  families  of  double  fluorides,  in  duorides- 
which  the  fluorides  of  boron,  silicon,  titanium,  and  of  other  electro- 
negative metals  are  the  acids,  and  the  fluorides  of  electro-positive 
metals  are  bases.  In  some  instances  hydrofluoric  acid  is  a haloid 

acid;  but  more  commonly  it  acts  the  part  of  a base. 

1544.  Hydrofluorides.  In  this  family  hydrofluoric  acid  is  com-  Hydro- 
bined  with  the  fluorides  of  electro-positive  metals.  If  an  equivalent  fluorides, 
of  any  electro-positive  metal  be  indicated  by  M,  then  the  general  for- 
mula for  this  family  is  MF-f-HF. 

1545.  Boro-fluorides.  When  the  terfluoride  of  boron  (fluoboric  Boro-fluo- 
acid  gas)  is  acted  upon  by  water,  one  out  of  every  four  eq.  of  the  rides- 
gas  interchanges  elements  with  water,  giving  rise  to  hydrofluoric 

and  boracic  acids,  the  former  of  which  combines  as  a haloid-base 
with  undecomposed  terfluoride  of  boron,  constituting  the  boro-hydro- 
fluoric acid,  but  which  may  be  viewed  as  the  boro-fluoride  of  hydro- 
gen. This  change  is  such  that 

4 eq.  terfluoride  of  boron  4 (B-|-3F)  -c  3 eq.  terfluoride  of  boron  3(B-j-3F) 

^3  3 eq.  hydrofluoric  acid  3(H-f-F) 

and  3 eq.  of  water  3 (H-f-O)  ^ and  1 eq.  boracic  acid  B-f-30 

By  careful  concentration  and  cooling,  the  boracic  acid  separates  as  a 
crystalline  powder,  and  the  boro-fluoride  of  hydrogen  remains  in  so- 
lution. It  is  strongly  acid  to  test  paper,  and  its  composition  is  indi- 
cated by  the  formula  HF-f-BF3  being  an  equiv.  of  each  fluoride. 

1546.  Boro-fluoride  of  Potassium.  It  is  prepared  by  dropping  Boro_fluo_ 
boro-fluoride  of  hydrogen  drop  by  drop  into  a solution  of  a salt  of  ride  of  po- 
potassa,  and  falls  as  a gelatinous  transparent  hydrate,  which  is  atassium- 
white  very  fine  powder  -when  dried.  It  has  a slightly  bitter  taste, 

and  is  quite  neutral  to  test  paper,  is  very  sparingly  soluble  in  alcohol 
and  cold  water,  but  is  dissolved  freely  by  hot  water,  and  subsides  on 
coolingin  small,  brilliant,  anhydrous  crystals.  At  a strong  red  heat 
it  gives  off  the  terfluoride  of  boron  and  fluoride  of  potassium  re- 
mains. 

1547.  Silico fluorides.  The  acid  solution,  called  silico -hydrofluoric  Silico-fluo- 
acid  may  be  viewed  as  the  subsesqui-silico  fluoride  of  hydrogen , andes- 
compound  of  157.16  parts  or  2 eq.  of  fluoride  of  silicon  and  59.04  or 

3 eq.  of  fluoride  of  hydrogen  (hydrofluoric  acid),  as  indicated  by  the 
formula  3HF-|-2SiF3.  When  the  solution  is  neutralized  with  po- 
tassa,  the  alkali  interchanges  elements  with  the  fluoride  of  hydrogen, 
water  and  fluoride  of  potassium  are  generated,  and  the  latter  com- 
bines with  the  fluoride  of  silicon.  This  double  fluoride  consists, 
therefore,  of  157.16  parts  or  two  eq.  of  fluoride  of  silicon,  and 
173.49  or  3 eq.  of  fluoride  of  potassium,  the  formula  of  which  is 
3KF+2SiF3.  A similar  change  ensues  with  the  protoxides  of  most 
other  metals,  and  hence  the  general  formula  of  the  silico-fluorides 
is  3MF^}-2SiF3.  On  exposing  these  compounds  to  a red  heat,  fluo- 
ride of  silicon  is  disengaged. 

1548.  Tit ano fluorides.  Hydrofluoric  acid  dissolves  titanic-acid,  Titano-flo- 
and  forms  with  it  an  acid  solution  which  may  be  viewed  as  the  rides- 
titano-fluoride  of  hydrogen.  When  mixed  with  potassa,  water  and 

46 


362 


Chap.  VI. 


Vegetable 

principles. 


Com- 

pounds. 

Simple 

bodies. 

Com- 
pounds of 
two  ingre- 
dients, 

Of  three, 


Of  four, 


Supposed 
difference 
in  affinities 
of  atoms  of 
organized 
and  unor- 
ganized 
bodies, 


Organic  Chemistry. 

fluoride  of  potassium  are  generated,  and  the  titano-fluoride  of  po- 
tassium results,  the  formula  of  which  is  KF-f-TiF2.  By  substitu- 
ting most  other  protoxides  for  potassa,  similar  salts  may  be  prepar- 
ed, the  general  formula  being  MF-)-TiF2. 


CHAPTER  VI. 

ORGANIC  CHEMISTRY. 

Section  I.  Vegetable  Bodies. 

1549.  The  chemical  principles  of  which  animals  and  vegetables 
are  Composed  are  exceedingly  numerous.*  We  can  seldom  obtain 
these  principles  in  a state  of  such  purity  as  to  enable  us  to  examine 
their  properties  with  accuracy,  unless  when  they  are  capable  of 
crystallizing,  or  of  entering  into  definite  compounds  with  acids  or 
alkalies. 

1550.  These  principles  are  all  compounds,  and  consist  sometimes 
of  two,  sometimes  of  three,  and  sometimes  of  four,  simple  bodies  uni- 
ted together ; but  seldom  of  more.  These  simple  bodies  are  hydrogen, 
carbon,  oxygen  and  nitrogen,  which  may  be  considered  as  constituting 
in  a great  measure,  the  basis  of  the  animal  and  vegetable  kingdoms. 

1551.  Organized  principles  composed  of  two  ingredients  are  of 
four  kinds.  1,  composed  of  hydrogen  and  carbon,  as  oil  of  turpen- 
tine; 2,  of  hydrogen  and  oxygen,  as  water;  3,  of  carbon  and  oxy- 
gen, as  oxalic  acid;  4,  of  carbon  and  nitrogen,  as  cyanogen. 

1552.  Those  composed  of  three  constituents  are  much  more  nu- 
merous. 

The  most  common  constituents  are  carbon,  hydrogen  and  oxy- 
gen. The  greater  number  of  the  acids,  alcohol,  ethers,  sugars, 
gums,  &c.,  are  thus  constituted. 

Some  few  organized  bodies  are  composed  of  carbon,  hydrogen, 
and  nitrogen.  Some  are  supposed  to  be  composed  of  carbon,  nitro- 
gen and  oxygen. 

1553.  The  organic  principles  composed  of  four  constituents,  con- 
sist of  carbon,  hydrogen,  nitrogen  and  oxygen,  united  in  various 
proportions.  The  number  of  atoms  of  nitrogen  contained  in  these 
compounds  is  generally  small  compared  with  that  of  the  other 
three  constituents,  agd  there  is  almost  always  a great  preponderance 
in  the  atoms  of  carbon  and  hydrogen  over  those  of  nitrogen  and 
oxygen. 

1554.  It  has  been  supposed  by  some  chemists  that  there  is  an 
essential  difference  between  the  affinities  which  unite  the  atoms 

* The  number  of  discoveries  which  have  of  late  been  made  in  this  department  of 
chemistry,  is  such  that  the  limits  of  this  work  will  not  allow  of  a full  account  of 
them.  For  minute  details  the  student  must  be  referred  to  the  recent  elaborate  work 
of  Thomson  : Chemistry  of  Organic  Bodies.  Vegetables.  London,  1838,  p.  1076, 
and  the  third  part  of  Liebig  and  Turner’s  Elements ; as  the  former  is  complete,  and 
comprises  an  account  of  all  the  recent  researches  of  the  European  chemists  in  this 
department,  it  will  be  employed  as  the  basis  of  this  chapter.  Of  Liebig’s  continua- 
tion of  Turner’s  Elements , but  100  pages  have  appeared.  The  letter  T will  refer  to 
the  first  and  L to  the  second. 


Vegetable  Principles . 363 

constituting-  organic  principles,  and  those  which  unite  the  atoms  of  Sect.  1. 
unorganized  bodies ; that  there  is  some  unknown  power  besides 
chemical  affinity,  which  interferes  with,  and  regulates  the  combina- 
tions and  decompositions  of  organized  bodies,  which  is  wanting  in 
those  that  are  unorganized.  The  great  difference  between  the  two 
classes  of  bodies  consists  in  this,  that  the  organized  are  much  more  numberof 
complicated  in  their  structure,  containing  a much  greater  number  atoms, 
of  atoms  than  the  unorganized.  Hence  they  are  much  more  unsta- 
ble, much  more  easily  decomposed,  and  much  more  liable  to  decom- 
position than  unorganized  bodies. 

1555.  The  prevailing  opinion  is  that  binary  compounds  alone  ex-  prevailing 
ist : that  is  to  say,  that  one  electro-negative  atom  is  only  capable  of  opinion, 
combining  with  one  electro -positive  atom.  Two  of  these  binary 
compounds  may  combine  together,  making  a new  binary  compound 

of  four  atoms.  Two  of  these  binary  compounds  may  combine 
with  each  other,  making  a new  binary  compound  of  eight  atoms. 

And  in  this  way  binary  compounds  may  be  formed  as  complicated 
as  any  that  exist.*  T.  3. 

1556.  Many  of  the  principles  or  definite  compounds  which  exist  Crystalli- 
in  the  vegetable  kingdom,  or  which  may  be  formed  from  vegetable  zable> 
bodies,  are  capable  of  crystallizing,  and  in  this  way  may  be  procur- 
ed in  a state  of  purity.  Others  are  volatile,  and  are  formed  or  driv-  yolati]e 
en  off  at  particular  temperatures.  Frequently  several  of  these  vola-  principles, 
tile  bodies  occur  together,  and  in  such  cases  we  have  scarcely  the 
means  of  obtaining  them  in  a state  of  purity  unless  when  they  en- 
ter into  definite  and  crystallizable  compounds  with  some  other  sub- 
stance. 

1557.  It  is  not  unlikely  that  all  the  vegetable  principles  may  be  All  may 
found  hereafter  to  be  capable  of  entering  into  definite  compounds  form  defi- 
with  other  bodies,  and  that  they  will  ultimately  be  possessed  of  the  pounj°sm' 
character  of  acids  or  bases.  But  there  are  many  which,  so  far  as 

our  present  knowledge  extends,  do  not  seem  capable  of  forming 
any  such  definite  compounds,  thus  caoutchouc  neither  combines 
with  acids  nor  bases.  We  must  consider  such  bodies  as  neutral. 

1558.  There  are  also  several  groups  of  bodies  which  have  been  Groups  dis- 
distinguished  by  a common  name,  some  of  which  neutralize  acids,  tinguished. 
and  therefore  ought  to  constitute  bases,  while  others  of  the  same 

group  neutralize  bases,  and  therefore  ought  to  constitute  acids ; 
while  a considerable  number  has  been  so  imperfectly  examined  that 
we  do  not  know  whether  they  be  acids  or  alkalies.  This  is  the 
case  with  the  group  of  bodies  distinguished  by  the  name  of  vola- 
tile oils. 

1559.  Inconsequence  of  the  imperfect  state  of  our  knowledge  Temporary 
of  these  and  various  other  groups  similarly  circumstanced,  a tempo-  ^medfate" 
rary  class  may  be  formed  under  the  name  of  intermediate  bodies,  bodies, 
which  will  disappear,  when  the  investigation  of  vegetable  principles 

has  made  greater  progress. 

1560.  All  the  vegetable  principles  may  be  arranged  under  the  Four  class- 


* Thomson  dissents  from  this,  and  remarks  that  at  present  we  have  no  means  of 
knowing  how  the  numerous  atoms  that  constitute  organic  principles  are  grouped  to- 
gether. 


364 


Chap.  VI. 


Theory  of 
amides. 


Amide, how 
applied. 


Liebig’s 
application 
of  amide. 


Organic  Chemistry. 

four  following  classes  : — l.  Acids.  2.  Alkalies.  3.  Intermediate 
principles.  4.  Neutral  principles. 

1561.  Before  describing-  the  characters  of  the  various  principles, 
and  to  render  the  new  terms  intelligible,  it  will  be  proper  to  notice 
the  results  of  the  late  investigations  of  Wohler,  Liebig,  Pelouse 
and  Dumas. 

1562.  Theory  of  Amides , or  Amidets.  If  we  represent  the  com- 
position of  oxalic  acid  by  the  formula  C203,  and  that  of  ammonia 
by  NH3,  we  rrlay  represent  oxalate  of  ammonia  by  C203-)-NH3.  It 
was  observed  by  Dumas,  that  when  crystallized  oxalate  of  ammonia 
is  distilled  there  is  obtained,  among  other  products,  a white  tasteless 
powder,  which  he  distinguished  by  the  name  of  oxamide .*  On  an- 
alyzing this  he  found  it  composed  of  C202+NH2.  It  is  therefore 
oxalate  of  ammonia  deprived  of  an  atom  of  water.  When  heated 
with  potassa,  ammonia  is  disengaged,  and  oxalate  of  potassa  formed. 
By  this  treatment,  therefore,  it  converted  into  oxalate  of  ammo- 
nia, and  of  course  must  have  resumed  the  atom  of  water  which  it 
had  lost. 

1563.  The  term  amide , has  been  generalized  and  is  applied  to  all 
those  anhydrous  compounds  of  an  acid  and  ammonia  which  by  heat 
may  be  deprived  of  an  atom  of  water  ; or  to  all  those  compounds, 
which,  by  the  addition  of  an  atom  of  water,  can  be  converted  into 
a salt  of  ammonia. 

Benzoic  aqid  consists  of  C14H5O3 

Ammonia  . , t ' - H3N 

Benzoate  of  Ammonia  of  C14H5O3+H3N 

Now  Wohler  and  Liebig  obtained  a substance  to  which  they  gave 
the  name  of  Benzamide , composed  of  CuH50.-|-H2N,  so  that  it  dif- 
fered from  benzoate  of  ammonia  by  containing  HO  or  an  atom  of 
water  less.  Now  as  oxalate  of  ammonia  and  benzoate  of  ammonia 
are  in  all  probability  binary  compounds,  it  has  been  inferred  that  ox- 
amide  and  benzamide  are  also  binary  compounds,  thus 

Oxamide  ....  CX)*fH2N 

Benzamide  ....  ChHsO^HsN 

If  this  be  admitted,  it  will  follow  that  C202  and  CMHs02  are  com 
pounds  capable  of  existing  and  of  combining  with  other  bodies  ; and 
likewise  that  there  is  such  a compound  as  H2N. 

1564.  Liebig  applies  the  name  amide  to  the  hypothetical  com- 
pound of  two  atoms  of  hydrogen  and  one  atom  nitrogen.  If  potassi- 
um is  heated  to  the  point  of  fusion  and  a current  of  dry  ammonia 
passed  over  it,  hydrogen  gas  is  eyolved,  and  the  potassium  at  first 
increases  in  bulk,  loses,  the  metallic  lustre,  and  is  converted  into  a 
clear  liquid,  which  on  cooling  concretes  into  a gray  silky  mass;  it  is 
instantly  converted  into  potassa  and  ammonia  on  the  addition  of 
water.  It  is  called  potassamide , or  a compound  of 

1 atom  potassium  . . . . K 

1 “ of, H2N 

Potassamide  .....  K-j-H«jN 


* A contraction  of  oxalate  of  ammonia. 


Theory  of  Ethers. 


365 


Add  1 atom  water  . . . , HO  Sect.  1. 

and  we  have  ....  KO-I-H3N 

or  an  atom  of  potassa  and  an  atom  of  ammonia/ 

1565.  Dumas  has  given  to  these  compounds  the  name  of  arnidet . Amidets 
Thus  oxamide  he  calls  amidet  of  oxide  of  carbon  H2N-j-C202 ; C202  °* * * §  ^umas- 
being  a compound  similar  in  constitution  to  oxide  of  carbon,  which 

is  CO.t 

1566.  Theory  of  Benzoyl.  A remarkable  train  of  discoveries  has  Theory  of 
been  made  by  Wohler  and  Liebig  while  investigating  the  volatile  benzoyl’ 
oil  of  bitter  almonds.  They  have  led  to  the  inference  that  the  basis 

of  benzoic  acid  is  a substance,  to  which  they  have  given  the  name  of 
benzoyl  composed  of  C14H502. 

The  oil  of  bitter  almonds  is  a hydret ; or  . . C14H5O2+H 

Benzoic  acid  is  an  oxide,  or Ci4H502+0 

They  obtained  also  chloride,  bromide,  sulphuret  and  cyanide  of 
benzoyl. 

These  discoveries  render  it  almost  certain  that  benzoyl  exists  as  a 
separate  compound,  and  that  it  is  capable  of  combining  with  the  sup- 
porters of  combustion  and  cyanogen,  also  with  hydrogen,  sulphur, 
and  doubtless  other  simple  substances  or  compounds.  Similar  com- 
pounds have  been  discovered  by  Lowig  in  the  volatile  oil  of  spiraea 
ulmaria,  which  is  a hydret  of  spiroil.l  Analogy  leads  to  the  infer- 
ence that  other  (probably  all  the)  vegetable  acids  have,  like  the  ben- 
zoic, a base,  and  that  the  acid  is  a compound  of  that  base  with 
oxygen. 

1567.  Theory  of  Ethers.  According  to  Dumas  the  base  of  ether  Theory  of 
is  C4H4.§  Sulphuric  ether  is  C4H4+HO  ; oxalic  ether  is  (C4H4-)-  ethers. 
H0)-f-C203  and  so  on  of  the  others. 

According  to  Liebig,  the  radical  of  ether  isCjH5.  Sulphuric  ether  Liebig’s, 
is  an  oxide  of  C4H5,  and  is  represented  by  C4H5-(-0,  or  (for  shortness 
sake)  by  C4H50.  Alcohol  is  a hydrate  of  sulphuric  ether,  or 
C4H50+H0. 

The  radical  of  ether  is  capable  of  combining  with  chlorine,  bro- 
mine, and  iodine,  and  forms  chloric,  bromic,  and  iodic  ethers,  com- 
posed as  follows  : 

Chloric  ether  ....  C4H5-(-2Cl 

Bromic  .....  C4Hs+2Br 

Iodic  .....  C4H5-b2I 

All  the  oxygen-acid  ethers  are  combinations  of  an  atom  of  sulphuric 
ether,  which  possesses  the  characters  of  a base  with  an  atom  of  the 
acid. 

1568.  What  have  been  considered  as  alcohol  acids  are  merely  Alcohol 
combinations  of  one  atom  of  ether  acting  as  a base  with  two  atoms  of  acids, 
the  acid.  They  ought  rather  to  be  considered  as  salts,  consisting  of 

two  atoms  acid  united  to  one  atom  base,  than  as  acids  sui  generis. || 


* According  to  Kane  white  precipitate,  of  the  Pharnmcop.,  is  a morcuramide,  or  a 
compound  of  Hg+H2N. 

+ For  other  examples  see  Thomson.  7,  and  Dumas’  Chim.  appliqut , v.  S3. 

t A supposed  base. 

§ Called  by  Thomson  in  Chem.  of  Inorg.  Bodies,  Tetarto-carbohydrogen. 

||  Thomson  is  disposed  to  prefer  the  theory  of  Liebig  as  the  simplest,  and  as  agree- 
ing best  with  the  phenomena.  Liebig  has  extended  his  theory  much  farther,  and 
made  it  to  apply  to  sugars,  &c.  T.  9. 


366 


Organic  Chemistry. 


ChaP  vt-  1569.  Theory  of  Pyr acids.  There  are  several  vegetable  acids 
Theory  of  which,  when  distilled,  undergo  decomposition,  and  new  acids  are 
pyracids.  generated  by  the  process,  which  have  been  distinguished  by  the 
name  o (pyracids.  Thus  tartaric  acid  when  so  treated,  yields  pyro- 
tiorTaffect1* tariaric  ac^’  £aU‘c>  pyrogallic,  &c.  It  has  been  observed  by 
ed  by  heat.  Pelouze,  that  the  nature  of  the  decomposition  is  regulated  by  the 
degree  of  heat  applied.  When  the  heat  is  not  too  high,  the  acid  is 
resolved  into  a pyracid,  carbonic  acid  and  water,  or  sometimes  into 
a pyracid,  and  one  or  other  of  the  two  last  products.  Thus  when 
tannin  is  distilled  at  a heat  of  4S2°  it  is  resolved  into  carbonic  acid, 
water,  and  metagallic  acid.  Tannin  being  C18H30,2  three  atoms  of 
tannin  are  Now  these  three  atoms  are  resolved  by  the 

heat  into 

6 atoms  carb.  acid  . . =Cs  O12 

8 “ water  . = H*  0« 

8 “ metagallic  acid  . =C4*Hi6  0ig 


C54  H24  036 

When  gallic  acid  is  distilled  at  419°,  it  is  converted  into  pyrogallic  acid  and 
carbonic  acid, 

Gallic  acid  is  . . . C7  H3  O5 


Pyrogallic  acid  is  . 
Carb.  M is  . 


C6  Hj  O3 
C o2 


C7  H3  Os 

At  the  482°  no  pyrogallic  acid  is  formed,  but  only  metagallic  acid,  water,  and 
carbonic  acid, 

1 atom  gallic  acid  is  C7  H3  O5 


1 “ metagallic  “ 

1 “ carb.  acid  “ 

1 “ water 


=C6  Il2  02 
=C  O2 
= HO 


Theory  of 
substitu- 
tions. 


Dumas’s 

conclu- 

sions. 


C7  h3  o5 

Sometimes  the  saturating  power  of  a vegetable  acid  is  not  altered  by 
converting  it  into  a pyroacid  ; sometimes,  according  to  Pelouze,  it  is 
reduced  one  half.* 

From  these  observations  it  has  been  inferred  that  gallic  acid  is  a 
compound  of  pyrogallic  acid  and  water,  and  so  of  others. t 

1570.  Theory  of  Substitutions.  Oxygen,  chlorine,  bromine,  and 
iodine  may  be  made  to  unite  with  various  compound  bodies,  while  at 
the  same  time  these  bodies  give  out  hydrogen.  Thus  when  dry 
chlorine  gas  is  passed  into  pure  oil  of  bitter  almonds,  which  is  com- 
posed of  CuH5Oo-|-H,  it  loses  its  atom  of  hydrogen  which  con- 
stituted it  a hydret,  for  which  an  atom  of  chlorine  is  substituted, 
making  a compound  consisting  of  C14H502-|-CI,  which  is  a chloride 
of  benzoyl.  This  and  analogous  facts  have  been  generalized  by  Du- 
mas, who  has  drawn  from  them  the  following  general  conclusions. 

1571.  1.  When  a body  containing  hydrogen  is  subjected  to  the 


* Ann.  de  Chim.  et  Phys.  Ivi.  303. 

+ Thomson  does  not  agree  in  this  opinion  and  thinks  it  more  probable,  that  by  the 
temperature  applied,  a certain  portion  cf  the  carbon,  or  hydrogen,  or  of  both,  under- 
goes combustion,  and  that  the  remaining  atoms  arrange  themselves  so  as  to  constitute 
the  pyroacids- 


Compound  Radicals.  367 

dehydrogenizing  action  of  oxygen,  chlorine,  bromine,  or  iodine,  for  Ssct.  i. 
every  atom  of  hydrogen  that  it  loses  it  gains  an  atom  of  oxygen, 
chlorine,  bromine,  or  iodine.  2.  When  the  hydrogenous  body  con- 
tains water,  this  last  body  loses  its  hydrogen  without  anything  being 
replaced.  If,  after  this,  any  hydrogen  be  abstracted,  it  is  replaced  by 
a corresponding  number  of  atoms  of  oxygen,  chlorine,  &c.*  t. 

1572.  Laurentf  considers  the  base  or  radical  of  every  organic  Laurent’s 
body  to  be  a compound  of  carbon  and  hydrogen  united  together,  so  view, 
that  the  atoms  of  the  carbon  bear  a simple  relation  to  those  of  the 
hydrogen.  When  these  radicals  are  subjected  to  a dehydrogenizing 
process,  as  by  passing  a current  of  chlorine  through  them,  they  gra- 
dually lose  their  hydrogen  or  a part  of  it,  but  gain  as  many  atoms  of 

the  dehydrogenizing  body  as  they  lose  of  hydrogen.  So  that  if  we 
add  the  number  of  atoms  of  the  new  body  to  those  of  hydrogen  re- 
maining, the  sum  will  make  up  the  number  of  atoms  of  hydrogen 
originally  present  in  the  radical. 

1573.  The  dehydrogenizing  body,  or  a part  of  it,  being  converted 
into  water,  nitric  acid,  hydrochloric  acid,  &c.,  may  either  be  disen- 
gaged or  remain  combined  with  the  new  compound  formed. 

1574.  The  fundamental  radical  and  its  derivatives  will  be  neutral  Neutral 
or  alkaline,  whatever  be  the  portion  of  oxygen,  hydrogen,  &c.  enter- 
ing into  it.  But  when  the  oxygen,  &c.  enters  into  combination  with  Acid< 
the  radical,  it  renders  it  acid , how  small  soever  the  uniting  portion  Effect  of 
may  be.  Those  bodies  which  enter  into  combination  without  being  heat. 

a part  of  the  radical,  may  be  removed  by  heat,  alkalies,  &c.,  without 
being  replaced  by  anything  else.  But  when  a body  constitutes  a 
part  of  the  radical,  this  cannot  be  done.  T.  13. 


1575.  Liebig  has  termed  certain  compound  bodies,  which  have  the  Compound 
property  of  uniting  with  simple  bodies,  compound  radicals.  Those  Ja.c,^c.als  of 
which  unite  with  hydrogen  give  rise  to  hydracids.  He  has  arranged  Lle  lg‘ 
these  combinations  in  groups,  according  to  the  radical  of  each  ; the 
individual  members  of  each  group  arising  from  the  combinations  of  the 
radical  with  the  elements,  and  from  the  union  of  the  compounds  thus 
formed  with  other  compound  bodies. 

1576.  Whenever  one  or  more  of  the  constituent  parts  is  removed  New  com- 
from  any  of  these,  a new  compound  of  another  radical  is  produced,  pounds. 
When  the  oxygen  has  been  removed,  and  its  place  supplied  by  its  Oxygen  re- 
equivalent of  sulphur,  a sulphur-compound  of  the  same  radical  is  moved- 
formed,  and  its  properties  are  similar  to  those  of  the  oxygen-com- 
pound. 

When  the  hydrogen  is  displaced,  and  its  position  occupied  by  its  Hydrogen, 
equivalent  of  chlorine  or  oxygen,  there  will  be  formed  either  a similar 
compound  of  a similarly  constituted  radical,  or  several  new  com- 
pounds of  a more  simple  radical. 

1577.  All  combinations  of  compound  radicals  not  containing  nitro-  Combina- 

gen,  are  reduced  when  exposed  to  the  action  of  oxygen  to  oxides  of  compound 
more  simple  radicals,  the  higher  or  lower  degree  of  oxidation  being  radicals  not 
dependent  upon  the  quantity  of  oxygen  present.  containing 


* For  examples  see  T.  Org.  Chem.  1 1 . 


t Ann.  de  Grim,  et  Phys.  Ixi.  128. 


368 


Chap.  VI. 

Decompo- 

sed. 


Action  of 

strong 

acids. 


Action  of 
potassa,  on 
compounds 
not  con- 
taining ni- 
trogen. 


Products. 


Action  on 
those  con- 
taining ni- 
trogen. 


Products: 


Destructive 

distillatiou, 

products. 


Organic  Chemistry. 

1578.  Organic  compounds  not  containing  nitrogen,  may  be  de- 
composed in  three  different  ways,  when  brought  into  contact  with 
concentrated  or  anhydrous  sulphuric  acid ; firstly,  the  acid  may 
withdraw  water  from  the  compound,  or  at  least  oxygen  and  hydro- 
gen in  the  proportions  in  which  they  form  water;  in  this  case  the 
other  component  parts  unite  into  one  or  more  new  compounds  ; thus 
oxalic  and  sulphuric  acids  give  rise  to  the  formation  of  water,  of  car- 
bonic oxide  and  of  carbonic  acid ; or,  secondly,  the  acid  may  at  the 
same  time  give  oxygen  to  a part  of  the  carbon  of  the  compound, 
when  the  above  products,  together  with  sulphurous  acid,  will  be  pro- 
duced; or,  thirdly,  the  acid  may  give  oxygen  to  the  hydrogen  of  the 
compound,  and  iu  this  case  be  converted  into  hyposulphurous  acid, 
which  usually  enters  into  very  intimate  combination  with  the  organic 
substance  thus  modified. 

1579.  By  the  action  of  strong  acids  upon  substances  containing 
nitrogen,  there  is  frequently  produced  through  the  medium  of  the 
constituents  of  water,  on  the  one  hand  ammonia,  which  combines 
with  the  acid,  and  on  the  other  an  oxide  of  a new  radical,  in  which 
all  the  carbon  of  the  original  compound  is  present.  Hydrocyanic 
acid  and  hydrochloric  acid  ; oxamid,  urea,  and  sulphuric  acid, 
&c.  &c. 

1580.  All  organic  compounds  not  containing  nitrogen,  are  decom- 
posed by  being  fused  with  hydrate  of  potassa,  and  if  the  latter  be 
present  in  sufficient  quantity,  the  decomposition  is  not  attended  with 
the  separation  of  carbon  ; the  products  which  are  formed  are  the 
same  as  those  resulting  from  the  action  of  powerfully  oxidizing’ 
agents;  water  is  generally  decomposed,  its  oxygen  unites  with  the 
carbon  and  hydrogen  of  the  substance,  while  its  hydrogen 
is  liberated,  and  either  escapes  in  the  form  of  gas,  or  enters 
into  some  new  combination.  The  resulting  products  of  this  decom- 
position may  be  either  ulmic,  acetic,  and  oxalic  acids,  oxalic  acid 
alone,  or  solely  carbonic  acid,  according  to  the  degreeof  temperature 
to  which  the  mixture  is  exposed. 

1581.  All  organic  compounds  containing  nitrogen  are  decomposed 
by  being  boiled  in  a solution  of  caustic  potassa,  or  by  being  fused 
with  the  hydrate;  the  products  are  generally  the  same  as  those  ge- 
nerated by  the  action  of  a strong  acid  upon  the  same  substances,  only 
that  with  potassa  the  ammonia  is  liberated,  while  the  oxide  of  the 
new  carbonized  radical  enters  into  combination  with  the  potassa. 
Many  substances  which  are  very  rich  in  nitrogen  are  converted, 
with  the  separation  of  a part  of  the  nitrogen  as  ammonia,  and  the 
absorption  of  oxygen,  into  cyanic  acid,  and  this,  by  uniting  with  the 
potassa  escapes  further  decomposition  ; in  this  case  the  fused  resi- 
due is  completely  decomposed  into  ammonia  and  carbonic  acid  by 
bein?  dissolved  in  a little  water  and  boiled. 

15S2.  When  organic  bodies  are  exposed  to  the  destructive  distil- 
lation, their  constituents  give  rise  to  the  production  of  new  volatile 
compounds  of  more  simple  radicals,  either  with  or  without  the  depo- 
sition of  carbon.  The  products  vary  with  the  temperature,  which 
gives  rise  to  the  division  of  the  distillation  into  several  periods.  In 
the  first  are  produced  organic  acid  of  more  simple  radicals,  carbonic 
acid,  water,  and  combustible  fluids,  which  admit  of  being  mixed  with 


869 


Vegetable  Acids. 

water.  Jn  the  second  period,  the  products  of  the  decomposition  of  Sect,  u. 
the  new  substances  formed  during  the  first,  are  generated  ; the  acids 
disappear,  their  oxygen  unites  with  a part  of  their  hydrogen  and 
carbon,  forming  more  simple  compounds,  as  carbonic  oxide,  carbonic- 
acid,  and  water,  a portion  of  the  carbon  is  generally  deposited,  while 
the  rest  unites  with  hydrogen,  giving  rise  to  volatile  or  fixed  oleagi- 
nous substances.  In  the  last  period,  only  charcoal  and  gases  are 
obtained  ; the  latter  generally  consisting  of  a mixture  of  carbonic 
oxide,  olefiant  and  light  carburetted  hydrogen  gases. 

Substances  containing  nitrogen  form,  under  the  same  circum- 
stances, ammonia,  and  sometimes  cyanic  acid  ; in  the  last  period, 
cyanogen  and  hydrocyanic  acid. 

1583.  When  an  organic  compound  is  exposed  to  a similar  decom-  Effect  of 
position  in  contact  with  a strong  base,  which  is  not  reduced  by  a red  j^r°en^c 
heat,  it  is  generally  decomposed  into  carbonic  acid,  which  remains  ’ 
in  combination  with  the  baseband  into  one  or  more  new  substances. 

Should  these  latter  contain  oxygen,  they  may  be  entirely  deprived  of  Oxygen  re* 
it  by  a new  distillation  with  the  base,  the  oxygen  giving  rise  to  ano- moved- 
ther  portion  of  carbonic  acid,  while  the  other  constituents  of  the  sub- 
stance are  obtained  in  the  form  of  solid,  fluid,  or  gaseous  compounds 
of  carbon  and  hydrogen,  l.  738. 


Section  II.  Vegetable  Acids. 

1584.  These  acids  may  be  divided  into  seven  sets — 1.  Volatile  Thomp- _ 
Acids,  or  those  which  may  be  volatilized  without  decomposition  ; 2.  s°ons0flvl 
Fixed  Acids , such  as  cannot  be  volatilized  or  distilled  over  without  acids, 
decomposition  ; and  these  may  be  subdivided  into  such  as  are  de- 
composed when  exposed  to  heat,  but  furnish  at  the  same  time  pyr- 

acids ; and,  3,  into  those  whose  pyracids  are  unknown.  4.  Oily 
Acids,  or  those  into  which  oils  or  wax  are  converted,  when  boiled 
with  potassa  or  soda.  The  combination  with  the  alkali  constituting 
soap.  5.  Acids  containing  nitrogen.  6.  Acids  imperfectly  exa- 
mined. 7.  Compound  Acids , consisting  of  a vegetable  principle 
united  to  a strong  mineral  or  vegetable  acid. 

1585.  Oxalic  Acid , 2C0-|-0,  2 eq.  carb.  oxide  1 oxy.=  Oxalic 
36.24.  (L.)  C203  =36.  (T.)  This  acid  was  discovered  by  Scheele  in  acid- 
1776.  It  occurs  in  several  plants,  particularly  of  the  genera  oxalis, 
rumex,  &c ; combined  with  potassa  in  roots  and  with  lime  in  several 
kinds  of  lichens.*  Oxalate  of  lime  is  also  an  ingredient  of  several  uri- 
nary calculi ; the  acid  is  a product  of  the  decomposition  of  uric  acid,  of 

all  organic  compounds  not  containing  nitrogen  when  oxidized  by  ni- 
tric acid,  or  acted  upon  by  hydrate  of  potassa,  or  by  permanganic 
acid  ; it  is  also  formed  by  the  decomposition  of  cyanogen  with  water 
and  ammonia.  L. 

1586.  It  is  obtained  by  digesting  by  aid  of  gentle  heat  one  part  of  sugar,  or  process 
better  still,  of  potato  starch,  in  5 parts  of  nitric  acid  of  sp.  gr.  1.42,  diluted  with 

10  parts  of  water,  as  long  as  gaseous  products  are  evolved  ; by  evaporation  the 
acid  is  obtained  in  crystals,  which  may  be  purified  by  a second  crystallization 
after  being  well  dried  on  paper  or  porous  earthen  ware. 

* Said  to  occur  in  Humboltine  with  oxide  of  iron  by  Rivero — not  confirmed  by 
Thomson’s  analysis.  See  his  Mineralogy , ii.  469. 

47 


370 


Chap.  VI. 


Process  2. 


Theory. 


Crystals, 


How  dis- 
tinguished 
from  Ep- 
som salts. 


Vegetable  Acids . 

When  prepared  on  the  large  scale  the  process  is  conducted  in  cylindrical  ves- 
' sels  of  earthern  ware,  which  are  heated  Ity  being  surrounded  with  warm  water ) 
on  a small  scale  it  may  be  made  in  a porcelain  dish.  From  12  parts  of  potato 
starch  5 of  the  acid  are  obtained.  The  mother  liquor  should  be  treated  with 
an  additional  quantity  of  acid,  and  again  warmed,  when  a second  crop  of  crys- 
tals will  be  formed  ; this  is  repeated  until  the  solution  is  quite  exhausted.  On 
account  of  the  cheapness  of  nitric  acid,  this  is  the  usual  process  now  adopted  in 

the  manufactories.  Any  N adhering  to  the  crystals,  may  be  removed  by  gently 
heating  them  in  a porcelain  dish,  or  by  repeated  crystallization.*  L. 

It  may  also  be  obtained  by  precipitating  a solution  of  the  superoxalates  of  po- 
tassa  by  acetate  of  lead  or  sulphuret  of  barium,  carefully  washing  the  precipitate, 

and  decomposing  it  while  yet  moist  by  dilute  S.  Filter  and  evaporate.  To  de- 
compose the  oxalate  of  lead  or  baryta  five  parts  of  strong  S must  be  employed 
diluted  with  ten  of  water  for  every  seven  parts  of  the  binoxalate  of  potassa. 

Nine  tenths  of  the  dilute  S is  to  be  added  in  successive  portions  to  the  moist  lead 
or  barytic  precipitate  ; sulphate  of  lead  or  baryta  is  instantly  formed,  and  the  ox- 
alic acid  is  dissolved  by  the  water.  After  the  mixture  has  stood  some  hours,  the 
clear  liquid  should  be  poured  from  tiie  precipitate,  which  should  be  repeatedly 
washed.  The  solution  yields  upon  evaporation,  crystals  of  pure  oxalic  acid  ; 
any  trace  of  lead  may  be  removed  by  hydrosulphuric  acid  gas.  The  residue  of  i 
sulphate  of  lead  or  baryta,  which  still  contains  some  undecomposed  oxalate,  , 

must  be  treated  with  the  remaining  tenth  of  the  dilute  S,  and  heated  with  a 
little  more  water  ; in  this  manner  an  additional  quantity  of  impure  oxalic  acid  is 

obtained,  but  the  8 may  be  separated  from  the  crystals  by  washing. 

1537.  The  production  of  oxalic  acid  from  organic  matter  is  a con- 
sequence of  the  oxidation  of  the  elements  of  the  latter  by  the  oxy- 

gen  of  the  N ; hence  those  substances  give  it  in  greatest  quantity  , 

which  contain  oxygen  and  hydrogen  in  the  same  proportion  as  I 

water.  In  the  second  process  sulphuret  of  potassium  and  oxalate  of  I 
baryta,  or  acetate  of  potassa  and  oxalate  of  lead  are  formed.  The  ] 

oxalate  of  baryta  or  lead  is  decomposed  by  S,  giving  rise  to  free  1 

oxalic  acid  and  sulphates  of  lead  or  baryta.  L. 

1558.  The  crystallized  acid  is,  according  to  Liebig,  a compound  of  I 
the  hydrate  with  water  of  crystallization.  The  crystals  are  trans-  I 
parent  oblique  rhombic  prisms,  with  one  or  two  terminal  planes,  one  U 
pair  of  the  lateral  edges  of  the  latter  is  sometimes  truncated. 

1559.  This  acid  has  no  odour;  tastes  and  reacts  strongly  acid,  ■ 
and  is  poisonous,  and  from  the  resemblance  which  the  crystals  bear  ■ 
to  those  of  Epsom  salt,  many  fatal  mistakes  have  arisen.  The  acid  ■ 
taste  is  in  itself  a sufficient  mark  of  distinction  ; or  without  tasting  J| 
it,  if  a few  drops  of  water  be  placed  on  a slip  of  the  dark  blue  pa-  1 
per  which  is  commonly  wrapped  round  sugar  loaves,  and  a small  I 
quantity  of  the  suspected  crystals  be  added,  if  it  be  oxalic  acid  iu I 
will  change  the  colour  of  the  paper  to  a reddish  brown.  The  so-  I 
lution  also  of  a small  quantity  of  this  acid  in  a tea-spoonful  of 
water,  will  effervesce  with  a little  scraped  chalk  or  whiting.  H. 
When  the  acid  has  been  swallowed,  copious  draughts  of  lime  water,  j 1 
or  magnesia  and  water,  should  be  administered,  and  vomiting  exci- 
ted as  speedily  as  possible. 


* If  shavings  of  wood  be  mixed  with  caustic  potassa,  and  exposed  to  a heat  consid- 
erably higher  than  that  of  boiling  water,  the  wood  suffers  decomposition,  and  is 

fmrtly  converted  into  oxalic  acid,  which  combines  with  the  potassa ; a process  fol 
owed  by  some  manufacturers  of  this  acid.  T. 


371 


Binoxalate  of  Potassa. 

1590.  The  crystals  when  heated  fall  into  powder,  and  lose  28  per  Sect-  11  • 
cent.  = 2 eq.  of  water  of  crystallization;  the  hydrate  of  oxalic  Effect  of 
acid  is  left.  When  rapidly  heated  to  the  temperature  of  350°,  they  heat* 
fuse  and  lose  their  water  of  crystallization,  a part  of  them  decom- 
posing, while  another  portion  sublimes  as  hydrate  in  dense  white 
fumes  of  a strong  odour,  which  cover  the  surface  of  the  fused  acid 

in  the  form  of  a woolly  crystalline  mass.  If  heated  in  a retort  to 
310°  it  is  decomposed  into  C,  C and  formic  acid. 

1591.  Heated  in  strong  S,  it  is  decomposed  into  C,  C and  water.  Decompo- 
The  anhydrous  oxalic  acid  may  be  considered  as  a compound  of  1 se^by  s 
eq.  C — | — 1 eq.  C,  which  accounts  for  the  production  of  equal  vols.  of 

the  two  gases  whenever  the  pure  acid  or  any  of  its  salts  is  heated  in 

strong  S (512). 

1592.  The  crystals  dissolve  in  eight  parts  of  water  at  60°,  in  their  Solubility, 
own  weight  of  boiling  water,  and  in  four  parts  of  alcohol  at  60°. 

When  pure  it  should  give  a precipitate  with  salts  of  baryta  that  is  Test  of 

perfectly  soluble  in  N,  if  it  contain  lead  it  is  blackened  by  hydrosul- 
phuric  acid  gas:  it  should  sublime  without  leaving  a residue. 

1593.  This  acid  and  its  soluble  salts  are  important  reagents  for 
detecting  and  separating  lime.^ 

1594.  By  distilling  oxalate  of  ammonia,  or  oxalates,  with  am-  Oxamide. 
moniacal  salts,  a substance  has  been  obtained  by  Dumas  which  he 

has  called  oxamide, t which  will  be  noticed  hereafter. 

1595.  Oxalate  of  Ammonia.  NH40C203+aq.  crystals.  This  is  Oxalate  of 
a very  useful  salt  for  the  purpose  of  separating  lime  from  magnesia, ammonia* 
and  generally  for  precipitating  lime  from  its  solutions. 

It  is  obtained  by  neutralizing  a solution  of  pure  oxalic  acid  by  Obtained, 
caustic  or  carbonate  of  ammonia,  or  by  decomposing  the  oxalate  of 
lead  by  sulphuret  of  ammonium,  and  evaporating  the  solution  to 
crystallization. 

It  may  also  be  prepared  by  neutralizing  the  bin-  or  quadroxalate  of  potassa  with 
carb.  of  ammonia ; the  first  crop  of  crystals  consists  of  oxalate  of  ammonia, 
which  may  be  completely  freed  from  potassa  by  repeated  crystallization,  the  mo- 
ther liquor  contains  the  neutral  oxalate  of  potassa. 

1596.  The  crystals  are  long,  colourless,  transparent  prisms,  of  the  Crystals, 
right  prismatic  system  ; with  a strong  saline  taste,  less  soluble  than 

the  oxalic  acid  and  efflorescent,  losing  12.6  per  cent,  of  water  of 
crystallization.  By  heat  it  is  decomposed,  giving  rise  to  oxamide. 

1597.  Binoxalate  of  Potassa.  H0.C203,K0.C203~|-2  aq.  eq.  = Binoxalate 
155.63.  This  salt  is  used  and  sold  as  the  essential  salt  of  lemons , of  potassa. 


* In  the  neutral  salts  of  oxalic  acid,  the  oxygen  of  the  base  is  to  that  of  the  anhy- 
drous add  in  the  proportion  of  l : 3.  If  the  oxygen  of  the  metallic  oxide  be  consid- 
ered as  a part  of  the  acid,  the  compound  contains  C and  a metal.  Many  salts  of  oxalic 
acid,  whose  bases  are  oxides  easily  reduced  to  the  metallic  state,  are  decomposed  by 
heat  into  C and  metal  (oxalate  of  silver  with  a slight  explosion).  The  oxalates  of 
the  alkalies  under  the  same  circumstances  evolve  C,  and  are  converted  into  carbo- 
nates. Many  metallic  oxides  when  heated  with  an  oxalate  are  reduced  by  the  C 
evolved.  There  exist  both  neutral  and  acid  salts  of  this  acid,  the  latter  contain  dou- 
ble, and  sometimes  four  times  as  much  acid  as  the  former.  (Liebig.) 
t Abbreviated  from  oxalic  acid  and  ammonia. 


372 


Vegetable  Jlcidt. 

Chap,  vi.  for  removing  iron-moulds  and  other  metallic  stains  (ink,  &c).  It 
exists  ready  formed  in  the  juice  of  the  oxalis  acetosella  or  wood  sor- 
rel, from  which  it  was  formerly  procured. 

Prepared.  1598.  It  may  be  made  by  neutralizing  one  part  of  crystallized  ox- 
alic acid  by  carbonate  of  potassa,  and  afterwards  adding  to  the  neutral 
salt  another  part  of  oxalic  acid  and  crystallizing.  The  crystals  are 
transparent  oblique  rhombic  prisms,  with  an  acid  taste  and  reaction. 

Properties.  It  is  poisonous.  Soluble  in  40  parts  of  cold  and  6 of  boiling  water. 

1599.  When  pure  it  should  fuse  and  decompose  without  emitting 
a burnt  odour,  and  the  residue  should  be  of  a gray,  not  of  a black 
colour.* 

Quadroxa-  1600.  Quadroxalate  of  Potassa  is  sold  in  commerce  as  binoxalate. 

late<  It  is  procured  by  dissolving  the  binoxalate  in  hydrochloric  acid  and 
crystallizing;  it  is  made  on  the  large  scale  by  neutralizing  one  part 
of  crystallized  oxalic  acid  and  adding  to  the  solution  three  parts  of 
the  pure  acid. 

Crystals.  1601.  Its  crystals  are  transparent  prisms  of  the  doubly  oblique 
prismatic  system  ; at  262°  it  loses  two  atoms  or  fourteen  per  cent, 
of  water,  at  higher  temperatures  oxalic  acid  passes  off  and  it  is 
decomposed.  If  pure  its  reaction  when  heated  is  similar  to  that  of 
the  binoxalate;  if  three  parts  are  converted  into  carbonate  by  a red 
heat,  and  added  to  a solution  of  one  part,  the  neutral  oxalate  should 
be  obtained. 

Oxalate  of  1602.  Oxalate  of  Lime , Ca0.C203-j-2  aq.  = S2.74,  occurs  in  se- 

lime.  veral  species  of  lichen,  of  which  it  forms  the  firm,  hard  skeleton,  so 
that  many  of  them  may  be  used  for  preparing  oxalic  acid,  but  not 
very  advantageously.! 

Distin-  1603.  The  insolubility  of  this  salt  in  water,  ammonia,  and  acetic 

guished.  acid,  an(j  jts  solubility  in  the  nitric  and  hydrochloric  acids,  distin- 
guishes it  from  most  other  precipitates.  Advantage  is  taken  of  this 
to  detect  lime  in  solutions  from  which  all  other  precipitable  metallic 
oxides  hare  been  separated  by  other  means,  the  alkaline  oxalates 
being  the  best  reagents  for  this  purpose;  thus  these  oxalates  are 
used  to  separate  lime  from  magnesia,  with  the  latter  of  which  they 
form  soluble  double  salts.  On  the  other  hand,  lime  may  be  used  to 
detect  oxalic  acid.t 

Colour,  &c.  1604.  Recently  precipitated  oxalate  of  lime  is  a snow-white  floc- 

culent  powder,  insoluble  in  acetic  acid,  readily  dissolved  by  free 
nitric  or  hydrochloric  acid,  and  by  a red  heat  is  converted,  without 
being  perceptibly  blackened,  into  carbonate  of  lime  ; from  the  weight 
of  which,  either  the  oxalic  acid  or  the  lime  may  be  calculated. 
L.  750. 


imparities  da-  *The  presence  of  cream  of  tartar  is  recognised  by  the  carbonaceous  residue,  and  the 
ucted.  peculiar  odour  which  it  emits  on  burning ; that  of  sulphate  of  potassa  by  the  common 

tests  of  S.  If  of  two  equal  parts  by  weight,  of  the  salt,  the  one  be  exposed  to  a red 
Irat,  and  the  other  be  dissolved  in  water,  the  solution  of  the  latter  should  be  deprived 
of  its  acid  reaction  by  the  addition  of  the  residue  of  the  former;  if  this  does  not  hap- 
pen, it  is  not  the  binoxalate  but  the  quadroxalate,  which  is  met  with  in  commerce  un- 
der that  name.  (Liebig.) 

t See  Braconnot’s  process  Ann.  do  Chim.et  Phys.  xxviii.  318,  and  Quart.  Jour.  xix. 
t It  should  be  remembered  that  oxalic  acid  is  imperfectly  precipitated  by  salts  of 
lime  from  a solution  which  contains  the  oxides  of  chromium,  iron,  or  manganese. 
(Liebig.) 


Formic  Acid. 


373 


1605.  j Rhodizonic  Acid.  C7H3O10.  When  a stream  of  dry  carbonic  Sect.  11. 
oxide  gas  is  transmitted  over  a portion  of  fused  potassium,  the  gas  is  Rhodizonic 
absorbed  in  large  quantity;  the  potassium  coats  the  surface  of  the  acid* 
glass  tube,  becomes  green,  and  at  last  a black  porous  mass  is  ob- 
tained, which,  if  exposed  to  the  air  when  warm,  inflames,  and  if 
covered  with  water  dissolves  with  the  rapid  evolution  of  a combusti- 
ble gas  ; if  moistened  with  water  it  burns,  and  forms  a red  solution 

which  contains  rhodizonate  of  potassa. 

1606.  This  compound  of  potassium  and  carbonic  oxide  was  Howob- 
obtained  by  Gmelin  in  considerable  quantity  as  a secondary  product  taincd. 
during  the  preparation  of  potassium  by  Brunner’s  process  (839), 
when  it  separates  from  the  gases  evolved  in  the  form  of  a gray  pow- 
der, which  may  be  readily  collected.  Exposed  to  moist  air  it  ab- 
sorbs water,  and  is  converted,  without  combustion,  into  rhodizonate 

of  potassa  of  a scarlet- colour  ; by  being  treated  with  alcohol,  in 
which  it  is  soluble,  the  free  potassa  may  be  separated.  All  its  com- 
pounds are  of  a red  colour,  or,  in  the  dry  state,  of  a brilliant  metallic 
green. 

1607.  The  changes  which  are  produced  on  rhodizonate  of  potassa  Remarka- 
when  Its  aqueous  solution  is  heated,  are  very  remarkable;  without  ble 

the  evolution  of  gases  it  is  decomposed  into  free  potassa,  oxalate  0fchan£es* 
potassa,  and  into  the  potassa  salt  of  a new  acid,  which  has  been 
called  by  Gmelin  the  croconic  acid.  l.  752. 

1608.  Croconic  Acid.  C504  = 62.  The  croconic  acid  is  prepared  Croconic 
by  adding  hydrofluosilicic  acid  to  a solution  of  its  potassa  salt,  and  eva-  acid- 
porating  to  dryness  ; the  pure  acid  is  removed  from  the  yellow  resi- 
due by  water;  it  is  yellow,*  readily  crystallized,  tastes  and  reacts 
strongly  acid,  is  soluble  in  water  and  alcohol  ; all  its  salts  are  yellow, 

and,  with  the  exception  of  the  ammoniacal  salts,  are  all  of  them 
insoluble  in  alcohol. 

1609.  Croconate  of  Potassa  crystallizes  in  long  six-sided  prisms,  Croconate 
of  an  orange-yellow  colour,  tastes  similar  to  nitre,  and  is  neutral  with  of  potassa. 
respect  to  vegetable  colours.  When  heated  it  loses  15  per  cent. 

= 2 eq.  winter  and  becomes  of  a lemon-yellow  colour.  It  burns  like 
tinder  into  a mixture  of  carbonate  of  potassa  and  carbon,  with  evolu- 
tion of  C and  C ; it  is  decomposed  by  chlorine  and  N with  effer- 
vescence into  peculiar  salts. 

1610.  Formic  Acid.  C2H  03  = 37.  This  acid  was  first  noticed  by  pormic 
Ray,  in  1671, t in  an  account  of  the  acid  spontaneously  given  out  by  acid, 
ants,  and  which  they  yielded  when  distilled.  In  1812  Gehlen  examined  History, 
it  and  pointed  out  some  of  its  characters.  It  has  been  since  ana- 
lyzed by  Berzelius,  and  an  artificial  method  of  preparing  it  discover- 
ed by  Dobereiner. 

1611.  It  may  be  obtained  from  ants  by  the  following  process  : 

Any  quantity  of  ants  may  be  infused  in  about  thrice  their  weight  of  water,  put  _ 

the  mixture  into  a silver,  or  tinned  copper  still,  and  draw  off  the  water  by  distillation  ” roceS3  or” 
as  long  as  it  continues  to  come  over  without  any  burnt  smell ; the  distillation  must 
be  stopped  as  soon  as  that  is  perceived  Saturate  the  water  in  the  receiver  with 
carbonate  of  potassa,  and  evaporate  to  dryness.  Mix  the  white  mass  thus  ob- 
tained with  as  much  sulphuric  acid,  previously  diluted  with  its  weight  of  water, 
as  is  sufficient  to  saturate  the  potassa.  Introduce  the  mixture  into  a retort,  and 


* Hence  its  name  from  crocus,  saffron . 


t Phil.  Trans. 


374 


Chap.  VI. 


Obtained 
from  sugar 
&c. 

Process. 


Concentra- 

ted. 


Emmet’s 

process. 


Detected. 


Liebig’s 

acid. 


Properties. 


Vegetable  Jlcids. 


distil  slowly  to  dryness.  The  liquid  which  comes  over  into  the  receiver  is  to  be 
' again  rectified  by  a very  moderate  heat,  to  get  rid  of  any  portion  of  sulphuric 
acid  that  may  be  present. 

1612.  It  may  be  prepared  from  sugar  and  many  other  vegetable 
» substances,  when  treated  with  binoxide  of  manganese  and  sulphuric 

acid.  The  following  process  has  been  pointed  out  by  Dobereiner. 

Dissolve  1 part  of  sugar,  starch,  &c.,  in  2 parts  of  water,  mix  the  solution  (in 
a large. vessel)  with  or  three  parts  of  binoxide  of  manganese  in  fine  powder. 
Heat  the  mixture  to  140°,  add,  by  little  and  little  at  a time,  3 parts  of  concen- 
trated sulphuric  acid,  previously  diluted  with  its  own  weight  of  water,  care- 
fully agitating  the  mixture  after  every  addition,  with  a wooden  rod.  After 
the  addition  of  the  first  third  of  the  acid  so  violent  an  effervescence  takes  place, 
that  unless  the  vessel  be  at  least  15  times  the  bulk  of  the  mixture,  a portion  will 
run  over.* 

1613.  A pound  of  sugar  yields  a quantity  of  the  acid,  capable  of 
saturating  five  or  six  ounces  of  carbonate  of  lime.  To  obtain  the 
formic  acid  in  a concentrated  state,  evaporate  the  formate  of  lime  to 
dryness,  and  mix  seven  parts  of  this  dry  salt,  in  powder,  with  ten 
parts  of  concentrated  sulphuric  acid  and  four  parts  of  water,  and  dis- 
til in  a retort  If  we  substitute  six  parts  of  alcohol  for  the  four  parts 
of  water  and  distil,  we  obtain  formic  ether. 

1614.  The  following  process  has  been  given  by  Emmet, t who  af- 
firms that  the  oxide  of  manganese  is  of  no  use  in  the  process. 

Mix  together  in  a retort  equal  measures  of  water,  oil  of  vitriol,  and  clean,  but 
unground  rye,  or  cracked  maize;  let  them  be  heated  to  the  boiling  point,  and  as 
soon  as  the  mass  has  become  thoroughly  blackened,  add  another  measure  of 
water  and  distil  otf  one  measure  of  formic  acid.  The  addition  of  more  water,  and 
fresh  distillation  will  afford  an  additional  quantity  of  a weaker  acid. 

1615.  The  presence  of  formic  acid  may  be  easily  ascertained. 
When  the  acid  or  formate  of  soda  is  put  into  a solution  of  any  salt  of 
gold,  platinum,  or  silver,  an  effervescence  takes  place,  C is  given  off, 
and  the  metal  is  deposited.!  When  formate  of  soda  is  mixed  with  a 
solution  of  corrosive  sublimate,  calomel  is  deposited.  When  the  acid 
is  added  to  a solution  of  nitrate  of  lead,  crystals  of  formate  of  lead  in 
needles  are  deposited. 

1616.  Liebig  has  found  that  formic  acid  maybe  obtained,  contain- 
ing only  one  atom  water,  by  decomposing  dry  formate  of  lead  by  hy- 
drosulphuric  acid.  When  of  this  strength  it  is  much  more  corrosive 

than  concentrated  S.  The  smallest  drop  applied  to  the  skin  occa- 
sions a sensation  like  that  produced  by  red-hot  iron.  A sore  is 
produced,  which  is  long  in  healing.  This  hydrate  crystallizes  at 
32°  and  boils  at  212°  like  water.  The  common  acid,  which  is  a bi- 
hydrate, crystallizes  at  5°  and  boils  at  226£°.§  Formic  acid  has  a 


* The  effervescence  is  owing  to  carbonic  acid.  Pungent  vapours  of  formic  acid  are 
exhaled.  To  preserve  these,  the  mixture  should  be  made  in  a copper  alembic  the  top 
of  which  should  be  put  on  and  connected  with  the  worm  in  the  refrigeratory.  When 
the  violence  of  the  effervescence  is  over,  the  rest  of  the  sulphuric  acid  is  to  be  added, 
the  mixture  is  to  be  agitated,  and  the  whole  distilled  over  almost  to  dryness.  A lim- 
pid acid  liquid  is  obtained,  having  a strong  smell,  and  consisting  of  water,  formic,  acid, 
and  nn  etherial  liquor.  Saturate  the  formic  acid  with  carbonate  of  lime,  and  distil  the 
liquor  a second  tune  to  preserve  the  etherial  liquid  which  comes  over  with  the  water, 
and  from  which  it  may  be  afterwards  separated  by  distilling  it  off  fused  chloride  of 
calcium.  T. 

t See  his  interesting  paper  in  Amer.  Jour,  xxxii.  140. 
i Ann.  d*  Chim.  et  de  Phys.  lii.  107.  § Jour,  de  Pharm.  xxi.  381 


Succinic  Acid . 


375 


considerable  resemblance  to  acetic.  Very  dilate  formic  acid  is  said  sect,  n. 
to  undergo  spontaneous  decomposition  like  vinegar.* 

1617.  Mellitic  Acid.  C404-(-H  = 57.48.  (L.)  Combined  with  alu- MeUitic 
niina  this  acid  constitutes  a rare  mineral,  mellite  or  honey-stone.  It  ac 
may  be  obtained  by  the  following  process  of  Wohler. 

Reduce  mellite  to  fine  powder,  digest  in  a solution  of  carbonate  of  ammonia;  Process, 
after  the  liquid  has  taken  up  all  the  mellitic  acid,  the  excess  of  ammonia  is  ex- 
pelled by  boiling;  filter,  evaporate  until  crystals  appear.  The  crystals  are  then 
dissolved  in  water,  and  acetate  of  lead  added.  The  mellitate  of  lead  is  decom- 
posed by  hydrosulphuric  acid.  The  solution  separated  by  filtration  from  the  sul- 
phuret  of  lead  yields,  on  evaporation,  a white  slightly  crystalline  powder ; it  is 
soluble  in  alcohol,  from  which  it  may  be  obtained  by  very  slow  evaporation  in 
radiated  groups  of  acicular  crystals. 

161S.  The  dry  acid  is  not  changed  by  boiling  in  N or  S.  The  Effect  of 
aqueous  solution  tastes  and  reacts  strongly  acid.  Boiled  in  alcohol,  heat>  &,c* 
it  seems  to  form  an  acid  mellitate  of  ether.  It  forms  salts  by  uniting 
with  the  base  ; its  alkaline  salts  are  soluble,  and  may  be  obtained  in 
crystals,  but  with  the  other  metallic  oxides  it  forms  either  insoluble 
or  very  sparingly  soluble  compounds.  These  salts  are  decomposed 
by  heat,  but  the  silver  salt  suffers  in  the  first  instance  a peculiar 
change  ; at  356°  1 eq.  of  water  is  separated.! 

1619.  Succinic  Acid.  C4H203,  = 50.  (T.)  This  acid  is  obtained  Succinic 

from  amber  ( succinum ),  and  hence  its  name.  acid> 

Fill  a retort  half  way  with  powdered  amber,  and  cover  the  powder  with  a Process, 
quantity  of  drj'  sand ; lute  on  a receiver,  and  distil  in  a sand-bath  without  em- 
ploying too  much  heat.  The  succinic  acid  attaches  itself  to  the  neck  of  the  retort. 

It  is  purified  by  dissolving  in  hot  water  and  putting  in  the  filter  a little  cotton, 
previously  moistened  with  oil  of  amber,  which  retains  most  of  the  oil,  and  allows 
the  solution  to  pass  clear.  It  is  subsequently  crystallized  by  gentle  evaporation, 
and  this  process  is  to  be  repeated  till  the  acid  is  sufficiently  pure. 

1620.  Succinic  acid  maybe  obtained  in  three  states:  1.  com- May  be  ob- 

bined  with  an  atom  of  water;  2.  with  half  an  atom;  and,  3.  anhy-^gg 
drous.  states. 

The  first  is  the  crystallized  acid  of  the  shops,  when  pure.  It  is 
soluble  in  water,  but  less  so  in  alcohol,  and  scarcely  at  all  in  ether. 

It  melts  at  356°  and  boils  at  455°.  When  the  crystallized  acid  is 
kept  for  a long  time  in  a retort  at  a temperature  between  266°  and 
284°,  it  undergoes  a remarkable  change.  A great  number  of  white 
needles  are  deposited  and  a little  water  is  disengaged.  These  nee- 
dles consist  of  succinic  acid  deprived  of  half  its  water,  while  the  por- 
tion in  the  retort  remains  unaltered. 

1621.  The  anhydrous  acid  may  be  obtained  by  distilling  a mix-  Anhydrous 
ture  of  dry  phosphoric  acid  with  crystallized  succinic  acid.  Theacid* 
best  method  is  to  fuse  the  succinic  acid  in  a retort,  and  then  add  the 
phosphoric  acid,  and  distil  slowly. 

Succinic  acid  dissolves  in  96  parts  of  water  at  50°,  in  24  parts  at  Solubility. 


* Thomson  states  that  he  has  preserved  for  several  years,  formic  acid  prepared  by 
Dobereiner’s  process,  dilute,  but  stronger  than  vinegar. 

+ Since  the  silver  salt,  dried  at  212°,  can  retain  no  water,  it  is  probable  that  the 
water  is  first  formed  at  the  above  heat  by  the  hydrogen  of  the  acid,  and  the  oxygen  of 
the  oxide  of  silver,  when  the  salt  passes  into  a combination  of  silver  and  carbonic  ox- 
ide C4O4,  the  latter  acting  the  part  of  chlorine  or  any  other  haloid  substance. 
(Liebig.) 


376 


Vegetable  Acids. 


Chap.  Vf. 
Succinates. 


Acetic  acid. 


Vinegar. 


Distilled  or 

acetous 

acid. 

Acetic  acid. 


Obtained. 


Pyroligne- 
ous acid. 


Properties 
of  acetic 
acid. 


52°,  and  in  2 parts  at  212°.  The  anhydrous  acid  is  less  soluble  in 
water  than  the  hydrous,  but  more  soluble  in  alcohol  and  ether. 

1622.  The  compounds  which  this  acid  forms  with  bases  are 
termed  succinates.  The  alkaline  succinates  are  soluble  in  water. 
This  is  not  the  case  with  succinate  of  baryta,  hence  baryta  is  preci- 
pitated from  a neutral  solution  by  succinate  of  ammonia.  This  salt 
likewise  precipitates  mercury  and  lead.  It  throws  down  iron  from 
all  solutions  provided  the  iron  be  in  the  state  of  peroxide  and  there 
be  no  excess  of  acid  present. 

1623.  Acetic  Acid,  C4H303  = 51.  (T.)  This  acid  is  employed  in 
three  different  states.  When  first  prepared  it  is  called  vinegar  ; when 
purified  by  distillation  it  assumes  the  name  of  distilled  vine  gar,  usually 
called  acetous  acid  by  chemists;  when  concentrated  as  much  as  pos- 
sible it  is  called  radical  vinegar  and  acetic  acid. 

1624.  Vinegar  is  usually  prepared  by  subjecting  liquids  that  have 
undergone  the  vinous  fermentation,  to  the  action  of  air  ; much  oxygen 
is  then  absorbed.  Many  solutions  of  vegetable  matter  produce 
vinegar.* 

When  distilled  at  a temperature  not  exceeding  that  of  boiling  wa- 
ter, till  about  two  thirds  or  five  sixths  of  it  have  passed  over,  most  of 
the  impurities  are  left  behind  and  the  product  is  pure  acid,  diluted 
with  water.  Distilled  vinegar  or  acetous  acid  is  transparent  and 
colourless,  of  a strong  acid  taste  and  an  agreeable  odour. 

1625.  To  obtain  acetic  acid,  or,  as  it  has  been  sometimes  called, 
radical  vinegar , distilled  vinegar  may  be  saturated  with  some  me- 
tallic oxide,  and  the  acetate  thus  obtained,  subsequently  decomposed. 
It  is  thus  procured  by  distilling  acetate  of  copper , or  crystallized  ver- 
digris, in  a glass  retort  heated  gradually  to  redness  : it  requires 
re-distillation  to  free  it  from  a little  oxide  of  copper  which  passes 
over  in  the  first  instance.  Acetic  acid  may  also  be  obtained  by 
distilling  acetate  of  soda  or  acetate  of  lead  with  half  its  weight  of 
sulphuric  acid  : or  from  a mixture  of  equal  parts  of  sulphate  of  cop- 
per and  acetate  of  lead  ; in  these  cases,  the  acid  passes  over  at  a 
moderate  temperature. 

1626.  A considerable  quantity  of  acetic  acid  is  also  now  procured 
by  the  distillation  of  wood  in  the  process  of  preparing  charcoal  for 
the  manufacture  of  gunpowder.  The  liquor  at  first  procured  is  usu- 
ally termed  pyroligneous  acid ; it  is  empyreumatic  and  impure,  and 
several  processes  have  been  contrived  to  free  it  from  tar  and  other 
matters  which  it  contains.  It  may  be  saturated  with  chalk  and 
evaporated,  by  which  an  impure  acetate  of  lime  will  be  obtained, 
and  which,  mixed  with  sulphate  of  soda,  furnishes,  by  double  decom- 
position, sulphate  of  lime  and  acetate  of  soda  ; the  latter  distilled 
with  sulphuric  acid  affords  a sufficiently  pure  acetic  acid,  which  by 
dilution  with  water  may  be  reduced  to  any  required  strength.  The 
purification  of  this  acid  has  been  brought  to  great  perfection.! 

1627.  Acetic  acid  obtained  by  the  processes  described  is  transpa- 
rent and  colourless,  its  odour  highly  pungent  and  it  blisters  and 
excoriates  when  applied  to  the  skin.  Its  specific  gravity  is  1.060. 


* For  other  details  see  Fermentation • 

t For  a full  account  of  the  processes  see  Ure’s  Did.  Arts  and  Man.  8. 


Acetic  Acid . 


377 


It  is  extremely  volatile,  and  its  vapour  readily  burns.  It  combines  Sect,  n. 
in  all  proportions  with  water,  and  when  considerably  diluted  resem- 
bles distilled  vinegar.  When  highly  concentrated,  it  crystallizes  at 
the  temperature  of  40°  F.,  but  liquefies  when  its  heat  is  a little  above 
that  point.  In  this  state  it  is  called  glacial  acetic  acid. 

1628.  Liquid  acetic  acid,  consisting  of  one  atom  acetic  acid, 

and  one  of  water,  which  has  a specific  gravity  of  1.06296,  does  not  Properties, 
redden  litmus  paper.  It  may  be  kept  in  contact  with  dry  carbonate 
of  lime,  or  even  boiled  over  it  without  disengaging  a single  bubble 
of  C gas,  or  combining  with  the  lime,  yet  it  dissolves  quicklime  in- 
stantly. It  decomposes  carbonate  of  potassa,  soda,  lead,  zinc,  strontia, 
baryta  and  magnesia,  disengaging  C.  When  mixed  with  several 
times  its  volume  of  alcohol,  it  loses  its  action  upon  these  carbonates.* 

1629.  Acetic  acid  possesses  but  little  energy  in  combining  with  Combining 
‘bases,  being  displaced  by  most  of  the  other  acids.  It  forms  with  power, 
bases  a class  of  salts  called  acetates , several  of  which  are  important. 

They  are  all  soluble  in  water.f 

1630.  When  the  vapour  of  alcohol  is  brought  into  contact  in  the 
atmosphere  with  the  black  powder  obtained  by  mixing  hydrochlorate 
of  platinum,  potassa  and  alcohol,  vinegar  is  rapidly  formed.  It  is  thus 
prepared  in  Germany.^ 


*Pelouze,  Ann.  de  Chim , et  de  Phys.  L 314i  t Thomson’s  Org.  Cham. 

t The  powder  is  called  Platina  Mohr  and  is  thus  made  : melt  platinum  ore  with  dou-  P]tttjna.Mohr 
b!e  its  weight  of  zinc,  reduce  the  alloy  to  powder,  and  treat  it  at  first  with  dilute  Process  for. 

S,  and  next  with  dilute  N,  to  oxidize  and  dissolve  out  all  the  zinc,  which  is  somewhat 
difficult,  even  at  a boiling  heat.  The  insoluble  black-gray  powder  contains  some  os- 
miuret  of  iridium  united  with  the  crude  platinum.  This  compound  acts  like  simple 
platina-black  after  it  has  been  purified  by  digestion  in  potash  ley,  and  washing  with 
water.  Its  oxidizing  power  is  so  great  as  to  transform  not  only  formic  acid  into  the 
carbonic,  and  alcohol  into  vinegar,  but  even  some  osmic  acid,  from  the  metallic  osmi- 
um. This  powder  explodes  by  heat. 

When  the  platina-mo/tr,  prepared  by  means  of  zinc,  is  moistened  with  alcohol,  it  ^ctionupon  al. 
becomes  incandescent,  and  emits  osmic  acid;  but  if  it  be  mixed  with  alcohol  into  a cohoi produces 
paste,  and  spread  upon  a watch-glass,  nothing  but  acetic  will  be  disengaged  ; afford-  acet‘cacid. 
ing  an  elegant  means  of  diffusing  the  odour  of  vinegar  in  an  apartments 

With  this  powder  vinegar  may  be  made  in  the  following  manner : Under  a large 
case,  which,  for  experimental  purposes  may  be  made  of  glass,  several  saucer-shaped 
dishes  of  pottery  or  wood  are  to  be  placed  in  rows,  upon  shelves  over  each  other,  a few 
inches  apart.  A portion  of  the  black  platina  powder  moistened  being  suspended  over 
each  dish,  let  as  much  vinous  spirits  be  put  into  them  as  the  oxygen  of  the  included 
air  shall  be  adequate  to  acidify.  This  quantity  may  be  inferred  from  the  fact,  that 
1000  cubic  inches  of  air  can  oxygenate  110  grs.  of  absolute  alcohol,  converting  them 
into  122  grs.  of  absolute  acetic  acid  and  64^  grs.  of  water. 

The  above  apparatus  is  to  be  set  in  a light  place  (in  sunshine,  if  convenient),  at  a 
temperature  of  from  68°  to  86°  F.,  and  the  evaporation  of  the  alcohol  is  to  be  promoted 
by  hanging  several  leaves  of  porous  paper  in  the  case,  with  their  bottom  edges  dipped 
in  the  spirit.  In  the  course  of  a few  minutes  the  mutual  action  of  the  platina  and  the 
alcohol  will  be  displayed  by  an  increase  of  temperature,  and  a generation  of  acid  va- 
pours, which,  condensing  on  the  sides  of  the  glass  case,  trickle  in  streams  to  the  bot- 
tom. This,  continues  till  all  the  oxygen  of  the  air  is  consumed.  If  we  wish  to  renew 
the  process,  the  case  must  be  opened,  and  replenished  with  air.  With  a box  of  12 
cubic  feet  in  capacity,  and  with  7 or  8 ounces  of  the  platina  powder  we  can  in  the 
course  of  a day,  convert  one  pound  of  alcohol  into  pure  acetic  acid,  fit  for  every  pur- 
pose, culinary  or  chemical.  With  from  20  to  30  lbs.  of  the  powder  (which  does  not 
waste),  we  may  transform,  daily,  nearly  300  lbs.  of  bad  spirits  into  the  finest  vinegar. 

589.64  parts  by  weight  of  alcohol  . . = H12  C4  Os 

consist  of  74.88  of  hydrogen  . . ==  H12 

305.76  of  carbon  . . = C4 

200.00  of  oxygen  . . =02 

48 


378 


Vegetable  Acids. 


Chap,  vi.  The  following  are  among  the  most  important  of  the  acetates : 

Acetate  of  1631.  Acetate  of  Ammonia  is  a very  deliquescent,  soluble  salt,  and 

ammonia,  extremely  difficultly  crystallizable.  In  solution,  obtained  by  satu- 
rating distilled  vinegar  with  carbonate  of  ammonia,  it  constitutes  the 
ammonia,  acetas  liquidus  of  the  U.  S.  P.  which  has  long  been  used 
in  medicine  as  a diaphoretic,  under  the  name  of  spirit  of  Mindererus . 
Of  potassa,  1632.  Acetate  of  Potassa  is  usually  formed  by  saturating  distilled 
vinegar  with  carbonate  of  potassa,  and  evaporating  to  dryness.  If 
this  salt  be  carefully  fused,  it  concretes  into  a lamellar  deliquescent 
mass  on  cooling.  It  is  the  terra  foliata  tartaric  and  febrifuge  salt 
of  Sylvius  of  old  pharmacy.  It  dissolves  in  its  own  weight  of  water 
at  60°,  and  the  solution  has  an  acrid  saline  taste. 

Of  lime,  1633.  Acetate  of  Lime,  is  a difficultly  crystallizable  salt,  readily 
soluble  in  water,  and  of  a bitter  saline  taste  consisting  of  1 at.  lime, 
1 at.  acid,  and  6 at.  water.*  It  is  sometimes  obtained  by  saturating 
the  vinegar  formed  during  the  distillation  of  wood,  and  employed  in 
the  preparation  of  acetate  of  alumina,  which  is  used  by  the  calico- 
printers  as  a mordant. 

Of  iron,  1634.  Acetate  of  Iron.  The  protacetate  is  formed  by  digesting 
sulphuret  of  iron  in  acetic  acid  ;t  it  yields  green  prismatic  crystals, 
of  a styptic  taste,  and  readily  soluble  in  water  ; the  solution  becomes 
brown  by  exposure  to  air,  and  passes  into  peracetate , which  is  un- 
crystallizable,  and  obtained  by  digesting  iron  in  acetic  acid.  This 
compound  is  used  by  calico-printers,  who  prepare  it  either  by  digest- 
ing iron  in  pyroligneous  acid,  or  by  mixing  solution  of  acetate  of 
lead  with  sulphate  of  iron,  and  exposing  the  filtered  solution  to  air. 
Of  zinc,  1635.  Acetate  of  Zinc , 1 at.  acid,  5 ox.  zinc,  7 water,  (T.)  is  form- 
ed either  by  dissolving  oxide  of  zinc  in  acetic  acid,  or  by  mixing  a 
solution  of  sulphate  of  zinc  with  one  of  acetate  of  lead.  It  crystal- 
lizes in  thin  shining  plates  of  a bitter  and  metallic  taste,  very  soluble, 
but  not  deliquescent.  This  salt  is  sometimes  used  in  pharmacy, 
chiefly  as  an  external  application. t 

Of  tin,  1636.  Acetate  of  Tin.  This  mineral  is  slowly  acted  on  by  acetic 

acid,  but  a protacetate  and  peracetate  of  tin  may  be  made  by  mixing 
acetate  of  lead  with  saturated  solutions  of  the  protochloride  and  per- 
chloride  of  tin.  These  solutions  have  been  recommended  as  mor- 
dants for  the  use  of  dyers.  The  protacetate  is  crystallizable.  Vine- 
gar kept  in  tin  vessels  dissolves  a very  minute  portion  of  the  metal ; 
and  in  pewter  vessels  it  likewise  dissolves  a small  portion  of  the 
lead,  where  in  contact  both  with  the  vinegar  and  air  ; hence  distilled 


if  we  combine  with  this  mixture  400  parts  of  oxygen  = O4 

we  have  of  water  337.44  . . = H6  O3 

acetic  acid  643.20  • = He  C4  O3 

Hence  100  parts  by  weight  of  alcohol  take  68.89  parts  of  oxygen,  and  there  are  pro- 
duced 58.11  parts  of  water,  and  110.78  of  acetic  acid.  Ure’s  Diet,  of  Arts  and  Manuf. 
2 and  1001. 

* Thomson 

+ According  to  Thomson  it  consists  of  1 atom  acetic  acid,  1 protoxide  of  iron,  3 
atoms  water. 

t According  to  Messrs  Aikin,  the  specific  gravity  of  a saturated  solution  of  acetate 
of  zinc,  made  by  digesting  the  salt  in  distilled  vinegar,  is  1055.  Of  this  solution  900 
grains  contain  53  of  dry,  or  82.6  of  crystallized  acetate.  One  ounce  by  measure  of  the 
solution  weighs  506  grains,  and  contain  29.8  grains  of  dry,  or  46.5  grains  of  crystallized 
salt. 


Acetates . 


379 


vinegar,  which  has  been  condensed  in  a pewter  worm,  affords  gene-  Sect- IL 
rally  traces  of  both  metals.^ 

1637.  Acetate  of  Copper.  By  exposing  copper  to  the  fumes  of  Acetate  of 
vinegar,  it  becomes  gradually  incrusted  with  a green  powder  called  copper, 
verdigris, t which  is  separable  by  the  action  of  water  into  an  insolu- 
ble subacetate  of  copper , and  a soluble  acetate. 

Acetate  of  copper  may  be  obtained  by  digesting  verdigris,  or  oxide 
of  copper,  in  acetic  acid  ; by  evaporating  this  solution,  it  is  obtained 
in  prismatic  crystals  of  a fine  green  tint.  It  dissolves  sparingly  in 
water  and  alcohol,  and  communicates  a beautiful  blue-green  colour 
to  the  flame  of  the  latter  ; by  distillation  it  affords  a very  pure  acetic 
acid. 

1638.  Acetate  of  Lead.  1 at.  acid,  1 protox.  lead,  3 water  (T).  of  lead, 
This  is  the  Sugar  of  Lead , and  Salt  of  Saturn  of  the  old  chemists  : 

it  may  be  regarded  as  the  most  important  of  the  acetates  ; it  is  used 
in  pharmacy,  and  by  dyers  and  calico-printers  for  the  preparation  of 
acetate  of  alumina  and  of  iron,  which  are  formed  by  mixing  its  solu- 
tion with  that  of  the  sulphates  of  those  metals,  an  insoluble  sulphate 
of  lead  being  at  the  same  time  produced.  Acetate  of  lead  is  formed 
by  digesting  the  carbonate  in  distilled  vinegar,  or  in  the  acetic  acid 
obtained  by  the  destructive  distillation  of  wood  ; it  usually  occurs  in 
masses  composed  of  acicular  crystals  ; the  crystalline  form  is  an 
oblique  angled  prism. I Its  taste  is  sweet  and  astringent,  and  it  is 
soluble  in  about  four  parts  of  water  at  60°. 

When  exposed  to  the  air  it  undergoes  no  change.  When  dissolved 
in  water,  a small  quantity  of  white  powder  falls,  which  is  a carbo- 
nate of  lead,  formed  by  the  carbonic  acid  which  usually  exists  in 
water,  or  a sulphate  when  sulphuric  acid  is  present.  If  carbonate  of 
lead  is  formed  a slight  addition  of  acetic  acid  renders  the  solution 
clear. 

1639.  The  sub-acetate  of  lead, § commonly  called  extr  actum  saturni,  Sub-acetate 
is  prepared  by  boiling  acetate  of  lead  with  litharge.  This  salt  is  less  of  iead’ 
sweet  and  less  soluble  in  water  than  the  acetate,  has  an  alkaline  re- 
action and  crystallizes  in  white  plates  by  evaporation.  It  is  decom- 
posed by  a current  of  carbonic  acid,  with  production  of  pure  carbonate 

of  lead ; and  forms  a turbid  solution.  It  appears  from  the  analysis 
of  Berzelius  to  consist  of  1 atom  of  acid  and  3 atoms  of  the  oxide  of 

lead.  Acetates  of 

1640.  Protacetate  of  Mercury  is  formed  by  mixing  a solution  of  ni-  mercury.  ° 

trate  of  mercury  with  acetate  of  potassa. 

* Vauquelin,  Ann.  de  Chim.  xxxii. 

t Diacetate  of  Thomson,  L atom  acid,  2 oxide  of  copper,  6 water.  According  to  Ure, 
verdigris  is  a mixture  of  crystallized  acetate  and  subacetate  in  varying  proportions. 

See  description  of  the  manufacture  in  Ure’s  Diet.  1273. 

The  composition  of  the  acetate,  as  stated  by  Thomson,  is  1 at.  acid,  1 oxide  copper, 

1 water.  Phillips  has  given  the  following  comparative  statement  of  the  composition 


of  the  different  kinds  of  verdigris  : 

Blue  Crystals. 

French  Verdigris. 

English. 

Acetic  acid  . 

28.30 

29.3 

29.62 

Peroxide  copper  . 

43.25 

43.5 

42.25 

Water 

28.45 

25.2 

27.51 

Impurity 

0 

2.0 

0.62 

100 

100 

100 

t Brooke,  in  Ann . Philos.  (2d  series)  vi.  374. 

§ Trisacetate  of  Thomson  who  has  described  several  acetates  of  lead,  for  an  account 
of  which  see  Inorg,  Chem.  ii.  642, 


380 


Vegetable  Acids . 


Chap.  VI. 


Acetate  of 

alumina. 


Lactic  acid. 


Effect  of 
heat. 


For  this  purpose  dissolve  three  ounces  of  mercury  in  about  four  ounces  and  a 
half  of  cold  nitric  acid,  and  mix  this  solution  with  three  ounces  of  acetate  of  po- 
tassa  previously  dissolved  in  eight  pints  of  boiling  water,  and  set  the  whole  aside 
to  crystallize,  which  takes  place  as  the  liquor  cools,  and  the  acetate  of  mercury 
then  separates  in  the  form  of  micaceous  crystalline  plates,  which  are  to  be  washed 
in  cold  water,  and  dried  on  blotting-paper.* * * § 

This  salt  has  an  acrid  taste,  and  is  very  difficultly  soluble  in  water, 
requiring,  according  to  Braconnot.t  600  parts  of  water.  It  is  inso- 
luble in  alcohol.  It  was  once  used  in  medicine. 4 The  peracetate 
is  formed  by  dissolving  red  oxide  of  mercury  in  acetic  acid,  and 
boiling  the  solution  on  fresh  oxide  till  the  acid  is  saturated. 

1641.  Acetate  of  Alumina.  This  salt  is  extensively  employed 
by  calico-printers  as  a mordant  or  basis  for  fixing  colours ; they  pro- 
duce it  by  mixing  solutions  of  alum  and  acetate  of  lead  : about  three 
pounds  of  alum  are  dissolved  in  eight  gallons  of  water,  and  a pound 
and  a half  of  sugar  of  lead  stirred  into  it;  a copious  formation  of  sul- 
phate of  lead  ensues  which  is  allowed  to  subside,  and  the  clear  liquor 
holding  acetate  of  alumina  and  a portion  of  undecomposed  alum  in 
solution,  is  then  drawn  off,  a portion  of  pearlash  and  chalk  being 
added  to  it  previous  to  use,  in  order  to  saturate  any  excess  of  acid. 

1642.  Acetate  of  alumina,  formed  by  digesting  recently  precipitated 
alumina  in  acetic  acid,  may  be  procured  in  deliquescent acicular  crys- 
tals of  an  astringent  taste,  and  containing,  according  to  Richter, 
73.81  acid  -(-  26.19  alumina  : hence  it  is  probably  a binacetate. 

This  salt  is  also  produced  by  the  mutual  decomposition  of  acetate 
of  lime  and  alurn.  A gallon  of  a solution  of  the  acetate,  of  a sp.  gr. 
of  about  1.050,  equivalent  to  nearly  half  a pound  avoirdupois  of  dry 
acetic  acid,  is  employed  for  every  2£  lbs  of  alum.$ 

1643.  Lactic  Acid.  C6H404  = 72.  When  milk  is  kept  for  some 
time  it  turns  sour,  and  to  the  acid  evolved  Scheele  gave  the  name 
lactic  ; it  has  since  been  obtained  from  several  vegetable  bodies  left  to 
spontaneous  fermentation.  Gay-Lussac  and  Pelouze  have  obtained  it 
from  the  beet  root  juice. II  It  is  colourless,  of  a syrupy  consistence, 
and  at  69°  has  a sp.  gr.  of  1.215.  It  has  no  smell,  but  is  extremely 

sour.  Water  and  alcohol  dissolve  it.  Boiled  with  concentrated  N 
it  is  converted  into  oxalic  acid.  It  dissolves  the  phosphate  of  lime 
of  bones  rapidly  ; boiled  with  acetate  of  potassa,  it  disengages  the 
acetic  acid. 

1644.  The  concentrated  acid,  heated  gradually,  becomes  more 
fluid,  darker,  and  gives  a white  solid,  which  when  pure  dissolves  in 
boiling  alcohol,  from  which  crystals  are  deposited  on  cooling.  The 
crystals  fuse  at  125°,  and  boil  at  4S2° : they  give  out  white  irritating 
vapours,  which  condense  upon  cold  surfaces  and  recrystallize  : they 
are  inflammable.  The  salts  formed  with  this  acid  are  termed  lac- 
tates.IF 


* Eklin.  Pharmacop.  In  preparing  this  salt,  the  quantity  of  water  for  dissolving 

the  acetate  need  not  he  so  large  as  above  directed,  one  pint  being  sufficient,  but  it  is 
necessary  to  pour  the  mercurial  solution  into  the  acetate. 

+ Ann.  de  Chim.  Ixxxvi.  92.  + Proust,  Jour,  de  Phys • lvi. 

§ Ure’s  Diet. — art.  Alumina. 

||  For  details  of  the  process  see  Thomson’s  Chem.  of  Org.  Bodies , 1.22. 

H Liebig  has  shown  that  the  acid  in  sauer  kraut  is  the  lactic.  Ann.  de  Pharm., 
xx  til.  113. 


Benzoic  Acid . 


381 


1645.  Benzoic  Acid.  This  acid  exists  in  gum  benzoin,  in  dragon  Sect,  n. 
blood,  &c.  ; it  is  formed  according  to  Liebig  by  the  oxidation  of  the  Benzoic 
hyduret  of  benzule^  in  the  air,  and  by  the  decomposition  of  many  ^id- 
compounds  of  benzule  and  of  hippuric  acid  and  amygdaline  by  oxidi- 
zing agents ; by  the  action  of  potassa  on  the  essential  oils,  cinnamon 
oil,  &c. 

Gum  benzoin,  in  coarse  powder,  alone  or  mixed  with  an  equal  weight  of  sand.  Process, 
is  spread  upon  the  bottom  of  a round  vessel  of  iron,  the  sides  of  which  should 
not  be  more  than  three  inches  high.  A sheet  of  dry  bibulous  paper  is  stretched 
tightly  over  the  opening,  and  fastened  to  the  sides  of  the  vessel  by  a little  paste. 

A hat  made  of  thick  paper,  and  of  the  common  form  of  a man’s  hat,  is  made  to  co- 
ver the  whole,  and  tightly  tied  to  the  sides  of  the  vessel  by  a strong  string.  The 
vessel  is  now  placed  upon  sand  spread  upon  an  iron  plate,  below  which  a fire  is 
kept  for  3 — 4 hours.  The  vapours  of  the  sublimed  benzoic  acid  pass  readily 
through  the  pores  of  the  bibulous  paper,  and  are  deposited  in  crystals  upon  the 
hat ; the  crystals  are  prevented  from  falling  back  into  the  iron  vessel  by  the  pa- 
per which  closes  its  opening.t  This  is  continued  as  long  as  a deposite  of  crys- 
tals is  observed. 


Or  in  the  moist  way  ; equal  parts  of  finely  powdered  benzoin  and  The  moist 
hydrate  of  lime  are  most  intimately  mixed,  and  then  boiled  for  se-  Udy' 
veral  hours  in  40  parts  of  water;  the  filtered  liquid  must  then  be 
evaporated  to  one  fifth  its  vol.  and  treated  with  hydrochloric  acid, 
when  the  benzoic  acid  will  crystallize  as  the  solution  cools. $ 

Or  hippuric  acid§  is  boiled  for  one  quarter  of  an  hour  in  nitric  acid  Another, 
of  sp.  gr.  1.42,  after  which  water  is  added  and  the  solution  allowed 
to  crystallize.  The  acid  obtained  from  gum  benzoin  is  purified 
either  by  a second  sublimation,  or  being  boiled  in  nitric  acid,  or  by 
passing  chlorine  gas  through  its  boiling  aqueous  solution. 

1646.  The  benzoic  acid  exists  ready  formed,  and  principally  in  a Ready 
free  state,  in  the  gum  benzoin,  from  which  it  is  separated  by  subli-  ^r^^nin 
mation.  On  boiling  hydrate  of  lime  with  gum  benzoin,  the  benzoic 

acid  is  dissolved,  and  the  resinous  parts  left ; by  a strong  acid  the 
benzoate  of  lime  is  decomposed,  and  the  benzoic  acid  separated.]! 

1647.  This  acid  crystallizes  in  soft  white  scales,  which  are  flexi- Properties, 
ble,  transparent,  and  of  a pearly  lustre  ; or  in  hexagonal  needles. 

When  pure  it  is  inodorous,  but  if  gently  warmed  it  smells  like  gum 
benzoin ; it  has  a slightly  biting  but  sweetish  taste,  produces  a burn- 
ing sensation  in  the  throat,  reddens  litmus  feebly,  fuses  at  250°,  sub- 


Suberic  Acid , CsHeOs,  is  obtained  by  digesting  cork  in  nitric  acid. 

Naphthalic  Acid,  see  Naphthaline. 

* Benzule  denotes  the  hypothetical  radical  of  a series  of  compounds  which  are 
produced  from  the  volatile  oil  of  the  bitter  almond  , or  are  connected  with  it  by  certain 
relations.  The  oil  of  bitter  almonds  itself  is  always  a product  of  the  decomposition  of 
amygdalin,  which  exists  in  the  kernels  of  most  stone  fruits,  and  in  the  leaf  of  the  lauro- 
cerassus,  from  which  it  may  be  obtained  in  a variety  of  ways.  Its  formula  is 
C14H5  O2  3 symb.  = Bz  3 eq.  = 106.68.  Liebig  and  Turner’s  Elem.  823. 

Benzule  has  not  been  obtained  in  a free  state,  but  may  be  separated  from  one  sub- 
stance and  transferred  to  another  in  numerous  combinations. 

t Mohr. 

t If  less  lime  betaken,  or  if  a perfect  admixture  be  neglected,  the  whole  will  bake 
into  a solid  mass  in  the  boiling  water  3 in  this  case  the  hard  fragments,  after  the  whole 
has  cooled,  must  be  again  mixed  with  hydrate  of  lime. 

§ An  acid  obtained  from  the  urine  of  the  horse,  convertible  into  benzoic  acid,  see 
process  in  Thomson’s  Org . Chem.  47. 

||  For  an  economical  method  of  purifying  the  acid  see  Ann.  de  Chim.  et  Phys.,  lvi. 
443,  and  Thomson’s  Org.  Chem • 42. 


382 


Chap.  VI. 


Action  of 

chlorine, 

&c. 


Benzoate 
of  ammo- 
nia. 


Soluble  and 

insoluble 

beuzoate. 


Malic  acid. 


Process. 


Vegetable  Acids . 

limes  at  300°,  (an  appearance  of  light  is  frequently  observed  in  the 
dark,)  boils  at  462°,  yielding  a vapour  of  sp.  gr.  4.27. 

The  sublimation  may  be  beautifully  seen  by  suspending  a small  Fig.  188. 
branch  of  a shrub  within  a tall  glass  without  a bottom,  placing  a 
small  quantity  of  the  acid  upon  a plate  of  metal  on  a stand,  cover- 
ing it  with  the  jar  and  applying  the  heat  of  a lamp  to  vaporize  the 
acid  ; the  branch  will  be  covered  with  delicate  white  crystals  of 
the  acid. 

1648.  It  is  not  changed  by  chlorine,  or  by  being  boiled 

with  dilute  N,  but  by  the  fuming  acid  it  is  converted  into 
a yellow  resinous  substance  of  a strongly  bitter  taste.  It 

is  dissolved  by  concentrated  S,  but  falls  upon  the  addition  of  water. 
It  is  soluble  in  200  parts  of  cold  and  25  parts  of.  boiling  water.  Its 
formula  is  CHH503-f-aq.,  or  BzO-f-aq.  ; eq.  =123.68. 

1649.  Benzoate  of  Ammonia , NH40,  BzO,  is  prepared  by  dis- 
solving benzoic  acid  in  pure  concentrated  ammonia,  by  the  aid  of 
heat,  till  the  latter  is  saturated,  when  it  is  allowed  to  cool.  It  forms 
feathery  acicular  crystals,  which  deliquesce  in  a moist  air,  and  are 
soluble  in  absolute  alcohol.  The  acid  salt  is  formed  by  boiling  and 
exposing  to  spontaneous  evaporation  the  neutral  salt,  with  the  loss  of 
ammonia,  it  is  deposited  in  large  regular  crystals. 

1650.  The  soluble  benzoates  of  metallic  oxides  have  a strong  biting 
saline  taste,  and  are  decomposed  by  most  other  acids  with  the  sepa- 
ration of  benzoic  acid  ; the  same  change  occurs  with  the  insoluble 
salts,  when  the  acid  which  is  added  forms  a soluble  salt  with  the 
metallic  oxide.  The  benzoates  of  the  alkalies  are  decomposed  by 
destructive  distillation  into  carbonates,  and  a variety  of  new  products. 
Exposed  to  a red  heat  with  an  excess  of  hydrate  of  lime,  the  acid  is 
decomposed  into  benzole,*  and  carbonic  acid  which  unites  with 
the  lime.t  L. 

Fixed  Acids.  0 

1651.  Malic  Acid.  C4Ha04,  eq.  60.0.  The  existence  of  a peculiar 
acid  in  the  juice  of  apples,  was  shown  by  Scheele,  in  1785.  He  ob- 
tained it  by  adding  solution  of  acetate  of  lead  to  the  expressed  juice 
of  unripe  apples,  by  which  a malate  of  lead  was  formed,  and  after- 
wards decomposed  by  sulphuric  acid.  Vauquelin  obtained  it  by  a 
similar  process  from  the  juice  of  the  house-leek.  The  same  acid  ex- 
ists in  the  berries  of  the  mountain-ash , from  which  it  was  first 
obtained  by  Donovan  in  1815,  and  called  by  him  sorbic-acid  ; he  has 
given  the  following  process  for  its  preparation. $ 

Express  the  juice  of  the  ripe  berries,  and  add  solution  of  acetate  of  lead,  filter, 
and  wash  the  precipitate  with  cold  water,  then  pour  boiling  water  upon  the  filter, 
and  allow  it  to  pass  through  the  precipitate  into  glass  jars  ; after  some  hours  crys- 
tals are  deposited,  which  are  to  be  boiled  with  2.3  times  their  weight  of  sulphuric 
acid,  specific  gravity  1.090.  The  clear  liquor  is  to  be  poured  off,  and,  while  still 

*73.44  carb.+6  hyd.  = 79.44;  C12H6.  (Liebig.) 

t For  description  of  benzoates  see  Turner  and  Liebig’s  Elem.  827. 

Cinnamomic  Acid  was  obtained  by  Dumas  and  Peligot  from  oil  of  cinnamon, 
which  they  consider  a compound  of  hydrogen  and  tbe  base  of  this  acid  or  cinnamoyl. 
The  oil  they  term  hydrct  0/  cinnamoyl.  This  acid  occurs  in  old  oil  of  cinnamon  in 
large  yellow  crystals,  soluble  in  boiling  water. 

Esculic  Acid  is  obtained  from  the  horse-chestnut  ( Esculus  hippocastatum). 

t Phil.  Trans.  ISIS'. 


Tartaric  Acid . 383 

hot,  a stream  of  sulphuretted  hydrogen  is  to  be  passed  through  it,  to  precipitate  Sect.  II. 
the  remaining  lead ; the  liquid  is  then  filtered,  and  when  boiled  so  as  to  expel 
the  sulphuretted  hydrogen,  is  a solution  of  the  pure  vegetable  acid. 

Malic  acid  may  also  be  obtained  by  steeping  sheet-lead  in  the 
juice  of  apples  ; in  a few  days,  crystals  of  rnalate  of  lead  form,  which 
may  be  collected  and  decomposed  by  dilute  sulphuric  acid.^ 

1652.  Malic  acid,  when  carefully  prepared,  is  colourless  and  very  p 
sour.  It  forms  crystallizable  salts  with  many  of  the  metallic  oxides, 
and  its  salts  are  termed  malates. t 

1653.  Citric  Acid , C4H204,  eq.  60.0,  is  obtained  by  the  following  Citric  acid, 
process  from  lemon  or  lime  juice  : 

Boil  the  expressed  juice  for  a few  minutes,  and  when  cold,  strain  it  through  How  pre- 
fine linen;  then  add  powdered  chalk  as  long  as  it  produces  effervescence,  heat  parecj. 
the  mixture,  and  strain  it  as  before : a quantity  of  citrate  of  lime  remains  upon  F 
the  strainer,  which,  having  been  washed  with  cold  water,  is  to  be  put  into  a mix- 
ture of  sulphuric  acid  with  twenty  parts  of  water  : the  proportion  of  acid  may  be 
about  equal  to  that  of  the  chalk  employed.  In  the  course  of  twentyfour  hours 
the  citrate  of  lime  will  have  suffered  decomposition,  and  sulphate  of  lime  is 
formed,  which  is  separated  by  filtration.  The  filtered  liquor,  by  careful  evapo- 
ration, as  directed  for  tartaric  acid,  furnishes  crystallized  citric  acid.t 

In  different  states  of  purity  it  is  employed  by  the  calico-printers, 
and  used  for  domestic  consumption.  The  proportion  of  citric  acid 
afforded  by  a gallon  of  good  lemon-juice,  is  about  eight  ounces. § 

1654.  Citric  acid  may  be  obtained  from  currants  by  the  following  Process 

process  : with  cur' 

rants. 

Pound  the  currants  and  cause  them  to  ferment ; when  this  is  over,  distil  to 
separate  the  alcohol.  Saturate  the  hot  liquid  with  chalk  ; wash  the  citrate  of 
lime  with  water,  and  press.  Mix  the  citrate  of  lime  with  water,  and  reduce  to 
the  consistence  of  syrup ; decompose  by  sulphuric  acid  diluted  with  twice  its 
weight  of  water.  Saturate  the  citric  acid,  thus  obtained,  with  carbonate  of  lime  ; 
press  and  treat  as  before  with  sulphuric  acid.  Remove  the  colour  by  animal 
charcoal  and  evaporate. || 

1655.  Citric  acid  forms  prismatic  crystals  of  a very  sour  taste,  Characters, 
very  soluble  in  water,  and  containing,  according  to  Berzelius,  1 atom 

real  acid  -j-  2 atoms  water,  a portion  of  which  it  loses  by  exposure 
to  heat. 

1656.  Exposed  to  heat,  the  crystals  undergo  the  watery  fusion, 
and  the  acid  is  itself  decomposed.1T 

r Derivative  A.cids  nt 

1657.  Tartaric  Acid.  C4H205,  eq.  66.24.  5 Pyrotartaric.  acidtanC 

(_  Pyruvic. 

This  acid  exists  in  several  vegetable  substances  ; it  is  one  of  the 
sour  principles  of  many  fruits,  and  is  said  to  be  abundant  in  the  po- 
tato-apple. Tartaric  acid  is  generally  obtained  from  the  bi-tartrate 
of  pot  assa,  {purified  cream  of  tartar.) 

Mix  100  parts  of  this  salt  in  fine  powder  with  30  of  powdered  chalk,  and  gra- 
dually  throw  the  mixture  into  10  times  its  weight  of  boiling  water;  when  the  "?  • . 
liquor  has  cooled,  pour  the  whole  upon  a linen  strainer,  and  wash  the  white  0 ainln£* * * § 

* For  other  processes,  &c.,  see  Thomson’s  lnorg.  Bodies , ii.  76. 

t For  an  account  of  which,  and  of  the  acids  derived  from  the  decomposition  of  malic 
acid,  see  T.  Org.  Bodies , 63. 

t For  a mode  of  obtaining  it  from  gooseberries  see  Ann.  Philos.  N.  S.  iv.  152. 

Many  circumstances  which  have  not  here  been  alluded  to,  are  requisite  to  ensure 
complete  success  in  the  operation ; these  have  been  fully  described  by  Parkes,  in  his 
Chem.  Essays. 

§ Twenty  gals,  of  good  lemon-juice  afford  10  lbs.  of  crystals.  (Ure.) 

j|  Tillog  in  Ann.  de  Chim.  et  de  Phys.  xxxix.  222. 

IT  For  derivative  acids  see  T.  or  B.  62,  and  for  Citrates , B.  ii.  515. 


384 


Chnp  VI. 


Properties. 


Forms  dou- 
ble salts. 


Tartrate  of 
potassa. 


Bilartrate, 
or  crude 
tartar. 


Tartaric 
acid  test  for 
potassa- 


Impurities. 


Acts  as  a 

simple 

acid. 


Vegetable  Acids. 

powder  which  remains  with  cold  water;  this  is  a tartrate  of  lime;  diffuse  it 
through  a sufficient  quantity  of  water,  add  sulphuric  acid  equal  in  weight  to  the 
chalk  employed,  and  occasionally  stir  the  mixture  during  24  hours  ; then  filter, 
and  carefully  evaporate  the  liquor  to  about  one  fourth  its  original  bulk ; filter 
again,  and  evaporate  with  much  care  nearly  to  dryness;  re-dissolve  the  dry  mass 
in  about  6 times  its  weight  of  water,  render  it  clear  by  filtration,  evaporate 
slowly  to  the  consistency  of  sirup,  and  set  aside  to  crystallize. 

By  two  or  three  successive  solutions  and  crystallizations,  tartaric 
acid  will  be  obtained  in  colourless  crystals,  soluble  in  6 parts  of  wa- 
ter at  60°.  Their  primary  form  is  an  oblique  rhombic  prism.* 

1658.  The  crystals  melt  at  a heat  a little  exceeding  212°  into  a 
fluid  which  boils  at  250°  and  leaves  a semi-transparent  mass  on 
cooling,  slightly  deliquescent. 

The  aqueous  solution  of  tartaric,  in  common  with  the  other  vege- 
table acids,  soon  becomes  mouldy,  and  suffers  decomposition. 

1659.  Tartaric  acid  has  a great  tendency  to  combine  at  once  with 
two  bases  and  form  double  salts.  In  consequence  of  this  property  it 
prevents  antimony  from  being  precipitated  as  usual  by  water,  and 
even  hinders  alkaline  bodies  from  precipitating  solutions  of  the  me- 
tal in  acids  as  they  usually  do.  t. 

1660.  Tartrate  of  Potassa , (formerly  soluble  tartar ) is  formed  by 
saturating  the  excess  of  acid  in  tartar  by  potassa,  and  boiling.  Ac- 
cording to  Phillips,!  100  parts  of  tartar  require  43.5  of  sub-car- 
bonate of  potassa.  The  resulting  salt  is  soluble  in  less  than 
twice  its  weight  of  water ; it  forms  large  prismatic  crystals.  These 
contain  1 atom  acid,  I potassa,  and  water. 

This  salt  is  used  in  pharmacy  as  an  aperient ; it  is  the  potasses 
tartras  of  the  Pkarmacop.  Its  taste  is  saline,  and  somewhat  bitter. 

1661.  Bi-tartrate , or  Supertartrate  of  Potassa.  Tartar.  This 
substance  exists  in  considerable  abundance  in  the  juice  of  the  grape, 
and  is  deposited  in  wine  casks,  in  the  form  of  a crystallized  incrus- 
tation : called  argol  or  crude  tartar.  It  is  purified  by  solution  and 
crystallization,  which  renders  it  perfectly  white;!  when  in  fine  pow- 
der it  is  termed  cream  of  tartar. 

It  may  also  be  formed  by  adding  excess  of  tartaric  acid  to  a solu- 
tion of  potassa.  The  mixture  presently  deposits  crystalline  grains, 
and  furnishes  a striking  example  of  the  diminution  of  solubility  by 
increase  of  acid  in  the  salt.  Upon  this  circumstance  the  use  of  tar- 
taric acid  as  a test  for  potassa  depends,  for  soda  forms  an  easily 
soluble  supertartrate  and  consequently  affords  no  precipitate,  b. 
Its  constituents  are  2 at.  acid,  1 potassa,  2 water,  t. 

1662.  The  tartar  of  commerce  is  never  quite  pure.  According  to 
Thomson  it  contains  five  per  cent,  of  tartrate  of  lime.§  It  is  some- 
times adulterated  by  the  addition  of  pounded  quartz,  and  by  calca- 
reous spar  ; the  former  may  be  detected  as  an  insoluble  residue  by 
boiling  the  powdered  tartar  with  half  its  weight  of  potassa  or  of  bo- 
rax in  eight  parts  of  water;  the  latter  produces  effervescence  with 
dilute  hydrochloric  acid. 

1663.  Bi-tartrate  of  potassa,  it  is  observed  by  Gay-Lussac,  acts,  in 


* Brooke  in  Ann.  Philos,  vi.  N.  S.  t Remarks  on  Pharmacop. 

t See  process  B.  ii.  600,  and  Jour,  de  Phys.  i.  67. 

§ Inorg.  Chem.  ii.  433.  When  present  it  separates  in  tufts  ot  acicular  crystals  from 
the  hot  solution.  B.  502. 


Tartaric  Acid — Tartrates . 385 

many  cases,  like  a simple  acid,  and  even  dissolves  oxides  that  are  Sect,  n. 
insoluble  in  the  mineral  acids  and  in  the  tartaric  acid.  He  proposed 
its  use,  therefore,  in  mineral  analysis. 

1664.  When  exposed  to  heat,  tartar  fuses,  blackens,  and  isdecom- 
posed  : and  carbonate  of  potassa  is  the  remaining  result.  Provided  nea  ’ c‘ 
the  tartar  be  free  from  lime,  which  however  is  seldom  the  case,  this 
furnishes  a good  process  for  obtaining  pure  carbonate  of  potassa. 

The  aqueous  solution  of  tartar  becomes  mouldy  when  exposed  to  air, 
and  the  tartaric  acid  being  entirely  decomposed  leaves  a weak  solu- 
tion of  carbonate  of  potassa. 

The  component  parts  of  tartar  render  it  an  excellent  flux  in  the 
reduction  of  metallic  ores  upon  a small  scale,  its  alkali  promoting  se> 
their  fusion,  and  the  carbonaceous  matter  tending  to  reduce  the 
oxides. 

1665.  Tartrate  of  Potassa  and  Soda  is  prepared  by  saturating  Tartrate  of 
the  excess  of  acid  in  tartar,  with  carbonate  of  soda  ; it  is  the  tartras  potassa  and 
potasses  et  sodee  of  the  Pharmacop. ; it  forms  prismatic  crystals.*  It soda? 

has  long  been  used  in  pharmacy  under  the  name  of  Rochelle  Salt 
and  Sel  de  Seignette.  It  consists  of  1 atom  of  the  tartrate  of  potassa, 

1 atom  of  the  tartrate  of  soda,  and  10  atoms  of  water,  t.  i 1.793. 

It  is  frequently  made  extemporaneously  by  dissolving  equal 
weights  of  tartaric  acid  and  the  sesquicarbonate  of  soda  in  separate 
portions  of  water,  and  then  mixing  the  solutions.! 

1666.  Tartrate  of  Iron  and  Potassa.  This  is  the  Ferrum  tarta - Of  iron  and 
risatum  of  the  London  Pharmacop but  it  is  most  conveniently  em-  Potassa- 
ployed  as  a medicine  in  solution,  which  may  be  formed  by  digesting 

1 part  of  soft  iron  filings  with  4 of  tartar. 

This  mixture  should  be  made  into  a thin  paste  with  water,  and  digested  for 
some  weeks,  till  the  acid  is  neutralized,  fresh  portions  of  water  being  occasion- 
ally added  to  prevent  exsiccation.  The  solution  of  this  compound  which  con- 
tains the  iron  in  the  state  of  peroxide,  is  possessed  of  some  curious  properties, 
first  pointed  out  by  Phillips. t 

1667.  Tartrate  of  Potassa  and  Copper  is  formed  by  boiling  oxide  Brunswick 
of  copper  and  tartar  in  water:  the  solution  yields  blue  crystals  on  green- 
evaporation  ; or  if  boiled  to  dryness,  furnishes  one  of  the  pigments 

called  Brunswick  green. 

1668.  Tartrate  of  Antimony  and  Potassa — Emetic  Tartar.  This  Tartrate  of 
compound  may  be  obtained  by  boiling  protoxide  of  antimony,  with  antimony 
pure  supertartrate  of  potassa.  It  is  the  antimonium  tartarizaium  of  aad  Potas' 
the  London  and  U.  S.  Pharmacop. 

Emetic  tartar  may  be  prepared  by  boiling  a solution  of  100  parts  of  tartar  with  prepara_ 
100  parts  of  finely  levigated  glass  of  antimony,  or  of  the  sesquioxide ; the  ebulli-  tion  0f 
tion  should  be  continued  for  half  an  hour,  and  the  filtered  liquor  evaporated  to  emetic  tar- 
about  half  its  bulk,  and  set  aside  to  crystallize  ; octohedral  and  tertrahedral  crys-  tar. 
tals  of  the  emetic  salt  are  thus  obtained ; and  there  is  generally  formed  along 
with  them  a portion  of  tartrate  of  lime  and  potassa,  which  is  deposited  in  small 


* The  forms  of  its  crystals  arising  from  the  modification  of  a right  rhombic  prism, 
are  represented  by  Brooke  in  Ann.  Philos.  N.  S.  v.  451. 

t Soda  or  Sodaic  powders  of  the  shops  are  packed  in  two  distinct  papers,  the  one  blue  goda  derg 
and  the  other  white,  the  blue  containing  half  a drachm  of  carbonate  of  soda,  the  white  0 apow  er8, 
gr.  xxv.  of  tartaric  acid:  when  dissolved  and  mixed,  effervescence  takes  place,  but  the 
liquid  is  by  no  means  similar  to  “ soda  water.” 

? Experimental  Examination  of  the  London  Pharmacop.  98. 

49 


386 


Vegetable  Acids. 


Chap.  VI.  tufts  of  a radiated  texture,  and  which  may  easily  be  separated  when  the  mass  is 
dried.* 

1669.  Emetic  tartar  is  a white  salt,  slightly  efflorescent,  soluble  in 

about  14  parts  of  cold  and  2 parts  of  boiling  water.  It  is  decomposed 
by  the  alkalies,  and  when  heated  with  ammonia,  a portion  of  protox- 
ide of  antimony  is  thrown  down,  and  a very  soluble  compound 
remains  in  the  liquor.  Hydrosulphuric  acid  gas  produces  an  orange- 
coloured  precipitate  in  its  solution.  It  is  decomposed  by  bitter  and 
astringent  vegetable  infusions,  but  they  do  not  render  it  inactive  as  a 
medicine. t Phillips  has  shown  that  emetic  tartar  consists  of  1 atom 

bi-tartrate  of  potassa,  3 sesquioxide  of  antimony,  3 water. 

According  to  Thomson  emetic  tartar  consists  of  2 atoms  tartaric 
acid,  3 atoms  sesquioxide  of  antimony,  1 atom  of  potassa  and  2 
atoms  of  water.! 

C Derivative  Acids. 

1670.  Meconic  And.  C7H207  eq.  100.00.  < Pyromeconic  C10H3O4. 

f ftlelameconic  C12H4  O10. 

This  acid  exists  in  opium  and  was  discovered  by  Serturner  and  called 
meconic  acid  from  the  Greek  poppy.  It  is  procured  by  se- 

veral processes  of  which  the  following  is  recommended  by  Thom- 
son^ as  the  easiest. 

Make  an  infusion  of  opium  in  water  acidulated  with  sulphuric  acid.  The  in- 
Processfor.  fusion  is  mixed  wilh  chloride  of  calcium  in  sufficient  quantity  to  throw  down  the 
sulphuric  and  meconic  acids  in  combination  with  lime.  This  precipitate  is 
washed,  first  with  cold  water,  and  afterwards  with  boiling  alcohol.  It  is  next 
mixed  with  ten  times  its  weight  of  water,  and  heated  to  about  194°.  Add  by 
little  and  little,  agitating  violently,  a quantity  of  hydrochloric  acid,  sufficient  to 
dissolve  the  meconnte  of  lime,  which  constitutes  the  greater  part  of  the  precipi- 
tate. Pour  the  liquid  upon  a filter,  previously  washed  wilh  hydrochloric  acid. 
On  cooling,  light  and  brilliant  crystals  of  bimeconate  of  lime  are  deposited, 
which  are  to  be  dried  between  the  folds  of  a cloth  ; dissolve  them  in  hot  water, 
and  add  a sufficient  quantity  of  hydrochloric  acid  to  decompose  the  salt.  Keep 
the  liquid  for  some  time  hot,  but  under  212°  j on  cooling,  crystals  of  meconic  acid 
are  deposited. || 

To  deprive  it  of  colour,  saturate  by  a dilute  solution  of  caustic  potassa.  Dis- 
solve the  meconate  of  potassa  formed,  in  a small  quantity  of  hot  water ; let  it 
cool,  and  expose  the  resulting  magma  to  pressure.  Dissolve  and  crystallize 
anew,  and  finally  decompose  the  salt  by  hydrochloric  acid. 

Hare’s.  Hare  has  given  the  following  process  :1T  To  an  aqueous  infusion  of  opium  add 

acetate  of  lead,  collect  the  meconate  of  lead  by  a niter,  and  expose  it  to  hydro- 
sulphuric  acid  gas  ; the  meconic  acid  will  be  set  free.  The  solution  is  of  a red- 
dish amber  colour,  and  furnishes,  by  evaporation,  crystals  of  the  same  hue. 
Instead  of  hydrosulphuric  acid,  sulphuric  acid  may  be  used  to  liberate  the  meco- 
nic acid. 


Properties. 


Analysis. 


Meconic 

acid. 


Properties. 


1671.  Meconic  arid  crystallizes  in  white  transparent  scales.  It  is 


not  altered  by  cold  S or  hydrochloric  acid  ; dilute  N converts  it 


* Phillips,  in  his  Experimental  Examinations  of  the  London  Pharmacop .,  has 
stated  several  facts  respecting  the  formation  of  this  salt,  which  will  be  found  useful  to 
the  manufacturer.  See  Bigelow’s  Sequel,  75. 

t According  to  Orfila,  the  compound  of  tannin  and  oxide  of  antimony  is  inert,  and 
he  recommends  adecoctiou  of  ciucbona  bark  as  an  antidote. 

t Inorg.  Chem.  11.799.  For  an  account  of  racemic  acid  and  remarks  on  its  com- 
pounds see  T.  Org.  Chem.  67.  § Org.  Bodies , 80. 

||  If  the  crystals  are  mixed  with  bimeconate  of  lime,  repeat  the  treatment  with  hy- 
drochloric acid,  or  separate  the  crystals  of  bimeconate,  which  are  much  lighter,  by 
levigation.  T.  Chem.  Org.  Bodies , 80. 

IT  Amer.  Jour.  xii.  293.  For  other  processes,  see  B.  11, 535. 


Gallic  Acid . 


387 


into  oxalic  acid.  It  is  soluble  in  4 times  its  weight  of  hot  water ; Sect-  IL 
when  long  boiled  the  solution  becomes  yellowish,  then  red,  and  at 
last  deep  brown,  at  the  same  time  C is  disengaged,  and  the  acid  is 
changed  into  metameconic  acid,  which  is  no  longer  altered  by  the 
water.  This  change  may  be  produced  by  the  action  of  a water-bath 
continued  for  several  days.  The  new  acid  precipitates  during  the 
cooling.  It  consists,  according  to  Liebig,  of  carbon  41.54,  hydrogen 
2.07,  oxygen  56.39. 

1672.  Meconic  acid  combines  with  bases  in  three  proportions  and  Forms 
it  forms  with  them  neutral  salts  ; the  bisalts  strike  a very  deep  red  salts, 
with  the  persalts  of  iron,  which  disappears  when  the  iron  is  reduced 

to  protoxide,  but  re-appears  when  the  iron  is  again  peroxidized. 

The  meconates  are,  in  general,  insoluble  in  alcohol. 

1673.  When  nitrate  of  silver  is  poured  into  a solution  of  meconic  Action  of 

acid,  and  a little  more  N added  than  is  sufficient  to  dissolve  the  me-  silver?  °f 
conate  of  silver,  if  we  heat  the  liquid  the  salt  is  converted  into  cya- 
nide of  silver.  The  liquid,  at  first  limpid,  becomes  gradually  filled 
with  flocks  of  cyanide.  It  contains  also  oxalate  of  silver  in  solution. 


If  too  much  N be  added,  much  oxalate  of  silver  is  formed,  but  no 
cyanide.* 

C Derivative  Acids. 

1674.  Gallic  Acid.  C7H305,  eq.  85.00.  ] Pyrogallic  Ce  H3  03  £This 

4 ( Metagallic  Ci2H3  03  > 

acid  derives  its  name  from  the  gallnut , whence  it  was  first  procured 
by  Scheele.  It  may  be  obtained  by  several  processes,!  among  which 
the  following  deserve  notice  : 


Gallic  acid. 


% Moisten  bruised  gallnuts,  and  expose  them  for  four  or  five  weeks,  to  How  ob- 
a temperature  of  about  80°.  A mouldy  paste  is  formed,  which  is  to  be  squeezed  tained. 
dry,  and  digested  in  boiling  water;  it  then  affords  a solution  of  gallic  acid,  which 
may  be  whitened  by  animal  charcoal,  and  which,  on  evaporation,  yields  gallic 
acid,  crystallized  in  white  needles.? 

Boil  an  ounce  of  powdered  galls  in  16  ounces  of  water  down  to  8,  and  strain  ; 
dissolve  2 ounces  of  alum  in  water,  precipitate  the  alumina  by  carbonate  of  po- 
tassa,  and,  after  edulcorating  it,  stir  it  into  the  decoction  ; the  next  day  filter  the 
mixture ; wash  the  precipitate  with  warm  water,  till  this  will  no  longer  blacken 
sulphate  of  iron ; mix  the  washing  with  the  filtered  liquor,  evaporate,  and  the 
gallic  acid  will  be  obtained  in  acicular  crystals.§ 

1675.  Gallic  acid  when  pure  is  in  snow-white  needles,  requiring  properties. 
100  times  their  weight  of  cold  water  to  dissolve  them.  When 
dropped  into  a solution  of  persulphate  of  iron,  a deep  blue  precipitate 

falls,  which  dissolves  slowly  in  the  liquid,  and  after  an  interval  of 
some  days,  the  liquid  becomes  almost  colourless.  Sulphuric  acid 
removes  nearly  all  the  iron  and  protosulphate  of  iron  crystallizes. 

The  same  changes  are  quickly  produced  by  boiling,  with  the  disen- 
gagement of  C. 

1676.  Gallic  acid  forms  white  precipitates  with  baryta,  strontia,  Precipi- 
and  lime  water  which  redissolves  in  an  excess  of  acid.  Acetate  or  tates- 
nitrate  of  lead  produces  a white  precipitate,  not  altered  in  colour  by 
exposure  to  the  air. II 

* Liebig.  t For  others  see  T.  Inorg : Bodies , ii.  99,  and  B.  519. 

t Braconnot,  Ann.  de  Chim.  et  Phys.  ix.  181. 

§ Fiedler  in  Nicholson’s  Diet.  1.236. 

II  Pelouze  in  Ann.  de  Chim.  et  Phys.  liv.  348. 


388 


Vegetable  Acids. 


ChaP  VL  1677.  The  characteristic  property  of  gallic  acid  is  to  strike  a deep 
Character-  blue  with  the  salts  of  iron,  particularly  the  sulphate.  The  tannin, 
pertyPr°  which  is  another  constituent  of  nutgalls,  possesses  the  same  property. 

1678.  Gallic  acid  and  tannin  are  of  great  importance  in  the  forma- 
tion of  ink,  and  the  precipitate  formed  is  retained  in  suspension  by 
mucilage.* 

Kinicacid.  1679.  Kinic  Acid.  C15H909,  eq.  171.00.  \ j Kinicacid 

derives  its  name  from  having  been  discovered  in  Peruvian  bark.  A 
watery  infusion  of  the  bark  evaporated  to  a syrup  and  treated  with 
alcohol,  leaves  a viscid  mass  containing  kinate  of  lime  and  gum. 
Obtained  ^ solution  and  crystallization,  kinate  of  lime  may  be  procured  in 
crystals,  from  which  the  lime  may  be  separated,  by  dissolving  the 
kinate  in  water,  and  adding  sulphuric  or  oxalic  acid.  It  forms  solu- 
ble salts  with  alkalies,  and  metallic  oxides.t 

1680.  Tannic  Acid — Tannin.  CiSH80i2,  eq.  212.  This  substance 
Tannic  acid. exists  in  an  impure  state  in  the  excrescences  of  several  species  of 
oak,  called  gallnuts;  in  the  bark  of  most  trees;  in  some  inspissated 
juices,  such  as  kino  and  catechu  ; in  the  leaves  of  the  tea-plant,  su- 
Sources  mach  and  whortleberry  (uva  ursa),  and  in  astringent  plants  generally, 
being  the  chief  cause  of  the  astringency  of  vegetable  matter.  It  is 
frequently  associated  with  gallic  acid,  as  in  gallnuts,  in  most  kinds 
of  bark,  and  in  tea  ; but  in  kino,  catechu,  and  cinchona  bark,  little 
or  no  gallic  acid  is  present. 

It  may  be  prepared  pure  from  nutgalls  by  the  following  process  : 
Obtained.  Into  the  mouth  of  a flask,  fit,  by  grinding,  a narrow  glass  vessel,  fitted  with  a 
cork,  or  stopper,  at  the  upper  end.  Fill  the  bottom  of  the  long  narrow  glass  ves- 
sel, where  it  enters  the  flask,  with  a little  cotton,  and  place  above  the  cot- 
ton a quantity  of  nut-galls,  in  fine  powder,  filling  about  half  the  vessel.  Pour 
over  this  a sufficient  quantity  of  the  common  sulphuric  ether  of  commerce  to  fill 
the  rest  of  the  vessel.  Put  in  the  stopper  and  set  the  whole  aside.  The  follow- 
ing day,  there  will  be  found  in  the  flask  two  distinct  layers  of  liquid  : one  very 
light  and  fluid  in  the  upper  part ; the  other  heavier,  of  a light  amber 
colour,  occupying  the  bottom.  Pour  the  whole  into  a funnel,  stopping  the  bot- 
tom with  the  finger  ; let  it  remain  at  rest  for  a few  minutes,  till  the  two  liquids 


* To  make  twelve  gallons  of  good  ink,  we  may  take  nutgalls  12  lbs.,  green  sulphate 
jjjjj  of  iron  5 lbs.,  gum  Senegal  5 lbs.,  water  12  gals.  The  nutgalls  are  to  be  put  into  a 

cylindrical  copper,  of  a depth  equal  to  its  diameter,  and  boiled,  during  three  hours  with 
three  fourths  of  the  above  quantity  of  water,  adding  fresh  water  to  replace  what  is 
lost  by  evaporation.  Empty  the  decoction  into  a tuo,  draw  off  the  clear  liquor  and 
drain  the  lees.  Dissolve  the  gum  in  a small  quantity  of  hot  water,  filter,  and  add  to 
the  clear  decoction.  The  sulphate  of  iron  must  be  separately  dissolved  and  mixed. 
The  colour  darkens  by  exposure.  But  ink  is  more  durable  when  used  pale,  lire’s 
Diet.  Arts  and  Alan.  677. 

The  following  gives  a good  ink.  Bruised  galls  8 oz.,  sulphate  of  iron  4 oz.,  gum 
arabic  3 oz.,  sugar  candy  1 oz.  Boil  the  galls  in  twelve  pints  of  water  down  to  six, 
strain,  and  add  the  other  ingredients,  stirring  till  dissolved.  After  twentyfour  hours 
decant  and  bottle.  See  other  methods  in  B.  11.523. 

The  tendency  of  the  ink  to  become  mouldy  is  much  diminished  by  keeping  a few 
cloves  in  the  ink  bottle,  or  by  dissolving  in  each  pint  of  the  ink  about  three  grains  of 
corrosive  sublimate. 

The  colour  of  common  writing  ink  is  apt  to  fade,  in  consequence  of  the  decomposi- 
tion of  its  vegetable  matter  ; and  when  thus  illegible,  it  may  often  be  restored  by  wash- 
ing the  writing  with  vinegar,  and  subsequently  with  infusion  of  galls.  Acids  also 
destroy  its  colouring  matter,  and  those  inks  which  resist  their  actiou  contain  some 
other  colouring  principle,  usually  finely  powdered  charcoal.  Common  writing  ink  is, 
for  this  reason,  much  improved  by  dissolving  in  the  quantity  above-mentioned  about 
an  ounce  of  Indian  Ink,  which  is  lamp-black  made  into  a cake  with  isinglass.  See 
Macculloch  on  Indelible  Ink,  &c.  Brewster’s  Jour.  i.  318,  and  Bost.  Jour.  ii.  344. 

t For  details,  and  other  fixed  acids,  see  T.  Org.  Bodies,  89. 


Tannic  Acid. 


389 


separate ; allow  the  heavier  to  fall  into  a capsule,  and  set  the  lighter  portion  Sect.  II. 
aside  in  order  to  recover  the  ether,  of  whichit  principally  consists,  by  distillation. 

Wash  the  dense  liquid  two  or  three  times  with  sulphuric  ether  ; then  dry  it  in  a 
stove,  or,  in  vacuo , over  sulphuric  acid.  Much  vapour  of  ether  and  water  is 
disengaged ; the  bulk  increases,  and  a spongy  residue  is  left,  brilliant,  and  some- 
times colourless,  though  usually  yellowish.  This  substance  is  tannin  in  a pure 
state.  T.  109. 


1681.  Pure  tannic  acid  is  colourless  and  inodorous,  has  a purely 
astringent  taste  without  bitterness,  and  may  be  preserved  without  Froperties* 
change  in  the  solid  state,  very  soluble  in  water,  reddens  litmus,  and 
decomposes  alkaline  carbonates  with  effervescence.  Alcohol  and 

ether  dissolve  tannic  acid,  but  more  sparingly  than  water.  Solutions 
of  tannic  acid  do  not  affect  pure  protosalts  of  iron,  but  strike  a deep 
blue  precipitate  with  the  persalts  : a strong  solution  of  it  yields  a 
copious  white  precipitate  with  the  sulphuric,  nitric,  hydrochloric, 
phosphoric,  and  arsenic  acids,  but  none  with  the  oxalic,  tartaric,  lac- 
tic, acetic,  citric,  succinic,  and  selenious  acids.  It  is  precipitated  also 
by  the  carbonates  of  potassa  and  ammonia,  by  the  alkaline  earths, 
alumina,  and  many  solutions  of  the  second  class  of  metals.  With 
cinchonia,  quinia,  brucia,  strychnia,  codeia,  narcotina,  and  morphia, 
it  yields  white  tannates,  which  are  sparingly  soluble  in  pure  water, 
but  are  dissolved  readily  by  acetic  acid.  By  digestion  with  nitric 
acid  it  yields  oxalic  acid. 

1682.  A solution  of  tannic  acid  may  be  preserved  without  change,  Absorb§ 
provided  it  be  excluded  from  oxygen  gas  ; but  in  open  vessels,  it  gra-  oxygen, 
dually  absorbs  oxygen,  an  equal  volume  of  carbonic  acid  is  evolved, 

it  becomes  turbid,  and  deposits  a crystalline  matter  of  a gray  colour, 
nearly  all  of  which  is  gallic  acid.  After  digestion  with  a little  ani- 
mal charcoal,  the  gallic  acid  is  perfectly  white  and  pure.  There  is 
no  doubt,  therefore,  of  the  conversion  of  tannic  into  gallic  acid. 

1683-  Tannic  acid  is  distinguished  from  all  substances,  except  gal- 
lic acid,  by  forming  a deep  blue  precipitate  with  persalts  of  iron,  and  5]^^ 
from  gallic  acid,  by  yielding  with  a solution  of  gelatin  a white  flaky 
precipitate,  which  is  soluble  in  a solution  of  gelatin,  but  insoluble  in 
water  and  gallic  acid.  This  substance,  to  which  the  name  of  tanno - 
gelatin  has  been  applied,  is  the  basis  of  leather,  being  always  formed  Leather” 
when  skins  are  macerated  in  an  infusion  of  bark.  When  dried  it 
becomes  hard  and  tough,  and  resists  putrefaction.  Its  composition 
is  apt  to  vary,  according  to  the  relative  quantities  of  the  materials 
used  in  its  formation. 


To  a strong  solution  of  gelatin  (common  glue  answers)  add  a strong  infusion  of  £xp 
gallnuts,  the  white  precipitate  may  be  collected  upon  a glass  rod  and  pressed 
together,  forming  a tough  extensible  mass  resembling  new  leather. 

1684.  From  the  experiments  of  Davy,  it  appears  that  the  inner 
cortical  layers  of  bark  are  the  richest  in  tannic  acid.  Its  quantity  is 
greatest  in  early  spring,  and  smallest  during  winter.  Of  all  the 
varieties  of  bark  which  he  examined,  that  of  the  oak  contains  the 
largest  quantity  of  tannic  acid. 

1685.  The  various  kinds  of  tannic  acid  obtained  from  cinchona 
bark,  kino,  and  other  sources,  correspond  in  most  respects  with  that 
above  described  ; but  at  the  same  time  some  difference  is  observable, 
some  kinds  striking  a green  instead  of  a deep  blue  colour  with  the 


390 


Vegetable  Jlcids . 

chap,  vi.  persalts  of  iron.*  The  tannic  acid  from  catechu  is  less  highly  oxi- 
dized than  that  from  gallnuts. 

1686.  Artificial  Tannic  Acid.  This  substance  was  discovered  by 
Artificial I ^ Hatchett,  and  is  prepared  by  the  action  of  nitric  acid  on  charcoal.! 

For  this  purpose  100  grains  of  charcoal  in  fine  powder  are  digested  in  an  ounce 
of  nitric  acid,  of  density  J .4,  diluted  with  two  ounces  of  water,  with  a gentle  heat, 
until  the  charcoal  is  dissolved.  The  reddish-brown  solution  is  then  evaporated 
to  dryness,  in  order  to  expel  the  nitric  acid,  the  temperature  being  carefully  regu- 
lated towards  the  close  of  the  process,  so  that  the  product  may  not  be  decom- 
posed. 

Properties.  Artificial  tannic  acid  is  a brown  fusible  substance  of  a resinous 
fracture,  astringent  taste,  and  acid  reaction  ; soluble  in  cold  water  and 
in  alcohol.  With  a salt  of  iron  and  solution  of  gelatin  it  acts  pre- 
cisely in  the  same  manner  as  natural  tannic  acid.  It  differs,  how- 
ever, from  that  substance  in  not  being  decomposed  by  the  action  of 
strong  nitric  acid. 

1687.  Artificial  tannic  acid  is  generated  by  the  action  of  nitric 
acid,  both  on  animal  or  vegetable, charcoal,  and  on  pit-coal,  asphal- 
tum,  jet,  indigo,  common  resin,  and  several  other  resinous  substances. 
It  is  also  procured  by  treating  common  resin,  elemi,  assafaetida,  cam- 
phor, balsams,  &c.,  first  with  sulphuric  acid,  and  then  with  alcohol. 


Oily  Acids . 


Oily  acids.  16S8.  These  acids  are  so  called,  because  they  are  formed  from 
oils  or  fat,  and  enter  into  the  composition  of  soaps,  or  because  they 
possess  many  of  the  characters  of  oils.! 

Margaric  16S9.  In  1S13  Chevreul  made  Unown  an  acid  substance  which 
acid‘  enters  into  the  composition  of  soaps,  to  which  he  gave  the  name  of 
margarine  and  afterwards  distinguished  it  as  margaric  acid.  He 
found  that  this  acid  extracted  from  different  bodies  existed  in  two  differ- 
ent states,  and  as  the  one  contained  more  oxygen  than  the  other,  he 
distinguished  them  at  first  by  the  name  of  margarous  and  margaric 
acids.  But  he  afterwards  thought  better  to  give  to  margarous  acid 
the  name  of  stearic  acid,$  and  to  retain  the  term  margaric  acid  for 


the  latter. 

Stearic  1690.  The  method  of  procuring  stearic  acid  is  as  follows  : 
acid,  Make  a soap  by  boiling  mutton  6uet  and  caustic  potassa  together,  with  a suffi- 

Processfor,  cjent  quantity  of  water,  till  the  whole  is  converted  into  soap.  Dissolve  one  part 
of  this  soap  in  6 parts  of  warm  water,  and  mix  the  solution  with  about  40  parts  of 
cold  water,  and  leave  it  for  some  time  in  a temperature  about  60°,  or  between 
60°  and  70°.  A substance  precipitates  of  a pearly  lustre,  which  is  a mixture  of 
bistearate  of  potassa  and  margarate  of  potassa.  Collect  this  on  a filter  and  wash 
it.  The  liquid  that  has  passed  through  the  filter  being  mixed  with  a little  acid 
to  saturate  the  potassa,  will  yield  an  additional  quantity  of  this  two-fold  soapy 
salt.  By  repeaUng  this  process  several  times,  all  the  bistearate  and  margarate  of 
potassa  is  obtained,  and  the  water  retains  only  the  oleate  of  potassa.  The  bi- 
stearate and  margarate  of  potassa  is  to  be  dried  and  dissolved  in  about  20  times 
its  weight  of  hot  alcohol  of  0.82.  When  the  alcohol  cools,  a quantity  ofbistear- 


* These  have  been  distinguished  by  names  formed  from  that  of  the  substances  which 
afford  them.  See  Thomson,  Org.  Bodies , 112. 
i Phil.  Trans.  1805—6. 

t Thomson  includes  twentythree  acids  in  this  group.  They  were  first  distinguished 
by  Chevreul.  who  devoted  ten  years  to  tbe  assiduous  study  of  fixed  oils  and  fats.  A 
few  only  of  the  most  important  will  be  described  in  the  following  pages,  referring  to 
Thomson’s  work  for  the  study  of  the  greater  number.  § From  <map,  tallow. 


Azulmic  Acid. 


391 


ate  ot‘  potassa,  mixed  with  margarate,  precipitates,  and  oleate  and  margarate  of  po-  Sect.  II. 
tassa  remains  in  solution  in  the  alcohol.  By  repeated  solution  in  boiling  alcohol 
and  cooling,  the  two  substances  are  separated.  If  the  acid  does  not  now  melt  in 
water  till  the  temperature  rises  to  158°  it  is  pure  stearic  acid.  The  pure  stearate 
of  potassa  is  then  decomposed  by  boiling  with  hydrochloric  acid  and  water ; 
when  cool  the  stearic  acid  is  separated. 

1691.  Stearic  Acid,  C70H6O5,  eq.  527,  is  white,  tasteless,  and  des-  Properties, 
titute  of  smell,  insoluble  in  water  ; soluble  in  alcohol  at  167°  from 

which  it  crystallizes  at  122°,  becoming  solid  at  113°.  It  reddens  ve- 
getable blues  and  combines  with  bases  forming  salts  called  stearates. 

It  burns  like  wax. 

1692.  Margaric  Acid  * * * § C70H7(JO9,  eq.  562,  is  distinguished  from  Margaric 
the  last  by  melting  at  140°,  while  that  requires  a temperature  of acld> 

15S°.  When  it  is  distilled  with  lime,  a soft  matter  is  obtained,  which  • 

when  pressed  between  folds  of  blotting  paper,  gives  out  oil,  and  a 

white  substance  remains  which  has  been  named  margarone. 

1693.  To  obtain  pure  margarone  it  is  to  be  repeatedly  dissolved  Obtained, 
in  alcohol,  and  allowed  to  separate  by  crystallization.  It  is  white, 
brilliant,  and  has  a pearly  lustre.  It  is  a non-conductor  of  electricity 

and  becomes  electric  by  friction  and  pressure.  It  dissolves  in  fifty 
times  its  weight  of  boiling  alcohol,  of  sp.  gr.  0.S36  but  is  mostly  de- 
posited on  cooling;  is  incapable  of  forming  a soap.  It  differs  from 
margaric  acid  by  wanting  an  atom  of  carbonic  acid. 

1694.  Oleic  Acid , C70H62O7,  eq.  538,  is  obtained  from  soap  made  Oleic  acid, 
with  linseed  or  hemp  oil  with  potassa.  It  is  somewhat  coloured  and 

has  an  etherial  smell,  is  insoluble  in  water,  but  soluble  in  alcohol. 

It  decomposes  the  alkaline  carbonates,  reddens  litmus,  and  forms 
salts,  or  rather  soaps,  to  which  the  name  of  oleates  is  given.  It  burns 
like  the  fixed  oils. 

1695.  When  olive  oil  is  treated  with  half  its  weight  of  concen-  Action  ?f 
trated  sulphuric  acid  three  acids  are  obtained,  one  of  which  has  been  acjJ# 
called  sulpho-oleic,\  and  this  decomposed  affords  hydro-oleic  acid. 

From  the  last  named  acid  two  liquids  have  been  obtained  having  the 
same  composition  as  olefiant  gas,  one  of  these  boils  at  131°,  the  other 
at  230°.  The  first  has  been  recently  called  Olein,  the  second  Elain.  Olein. 

1696.  Olein  is  white,  very  liquid,  and  lighter  than  water,  with  a 
strong  odour,  very  combustible,  and  burning  with  a greenish  flame. 

Its  vapour  appears  to  be  poisonous. 

Elain  is  less  soluble  in  alcohol,  and  burns  with  a fine  white  flame.  ain‘ 
According  to  Thomson,  olein  is  composed  of  6 carbon  and  6 hydro- 
gen, and  elain  of  9 carbon  and  9 hydrogen4 

Acids  containing  Nitrogen .§ 

1697.  Azulmic  Acid . CSH4N404.  eq.  140.  Boullay  has  given  this  Azulmic 
name  to  an  acid  obtained  from  cyanogen  gas  that  has  undergone  spon- 
taneous decomposition.  It  is  insoluble  in  water,  but  is  dissolved  by  ni- 
tric acid  and  assumes  a beautiful  aurora-red  colour.  By  heat  it  is 


*From  [iMQyaQnrjs  a pearl.  tFremy,  Ann.  de  Pharm.  xx.  50. 

t Chlorophenisic  and  chlorophenesic  acids  have  been  obtained  from  coal-tar  by  Lau- 

rent, by  the  action  of  chlorine,  and  were  named  from  a supposed  base,  phene  (from 
(petty  on  I shine),  from  their  supposed  existence  in  oil  gas.  Ann.  de  Chim.  et  de  Phys. 
lxiii.  27.  For  details  see  T.  Org.  Bodies , 129. 

§ Of  these  Thomson  describes  eight. 


392 


Vegetable  Jlcids. 

Chap,  vi.  converted  into  hydrocyanate  of  ammonia,  and  a gas  is  evolved  which 
burns  with  a blue  flame  and  the  odour  of  cyanogen. 
acidg°tiC  1698.  Indigotic  Acid.  C.^H7£N1^015.  This  acid  is  obtained  by 
boiling  indigo  in  rather  dilute  nitric  acid,  formed  by  mixing  nitric 
acid  of  sp.  gr.  1.2  with  an  equal  weight  of  water.  To  the  solution, 
kept  boiling,  indigo,  in  coarse  powder  is  gradually  added,  as  long  as 
effervescence  continues ; and  hot  water  is  occasionally  added  to  sup- 
ply loss  by  evaporation.  The  impure  indigotic  acid,  deposited  in 
cooling,  is  boiled  with  oxide  of  lead  and  filtered,  in  order  to  separate 
resin  ; and  the  clear  yellow  solution  is  decomposed  by  sulphuric  acid, 
and  again  filtered  at  a boiling  temperature.  On  cooling,  the  acid 
crystallizes  in  yellowish-white  needles.  In  order  to  purify  them 
# completely,  they  were  digested  in  water  with  carbonate  of  baryta; 

and  the  indigotate  of  baryta,  deposited  from  the  hot  filtered  solution 
in  cooling,  was  dissolved  in  hot  water,  and  decomposed  by  an  acid. 
Indigotic  acid  was  thus  obtained  in  acicular  crystals,  of  snowy 
whiteness,  which  contracted  greatly  in  drying,  and  lost  their  crystal- 
line aspect ; but  the  dry  mass  was  dazzling  white,  and  had  a silky 
lustre. 

Properties.  1699.  Indigotic  acid  decomposes  carbonates,  but  is  a feeble  acid, 
and  reddens  litmus  faintly.  It  requires  1000  times  its  weight  of  cold 
water  for  solution,  but  is  soluble  to  any  extent  in  hot  water  and  alco- 
hol. Heated  in  a tube  it  fuses,  and  sublimes  without  decomposition; 
and  the  fused  mass,  in  cooling,  crystallizes  in  six-sided  plates. 
When  heated  in  open  vessels,  it  is  inflamed,  and  burns  with  much 
smoke.* 

Carhazotic  1700.  Carbazotic  Acid.  C,5N3015,  eq.  252.  This  name  has  been 

acid»  applied  by  Liebig  to  a peculiar  acid  formed  by  the  action  of  nitric 
acid  on  indigo. 

It  i9  made  by  dissolving  small  fragments  of  the  be9t  indigo  in  8 or  10  times 
their  weight  of  moderately  strong  nitric  acid,  and  boiling  as  long  as  nitrous  acid 
fumes  are  evolved.  During  the  action,  carbonic,  hydrocyanic,  and  nitrous  acids 
are  evolved  ; and  in  the  liquid,  besides  carbazotic  acid,  is  found  a resinous  matter, 
artificial  tannin,  and  indigotic  acid.  On  cooling,  carbazotic  acid  is  freely  depo- 
sited in  transparent  yellow  crystals  ; and  on  evaporating  the  residual  liquid,  and 
adding  cold  water,  an  additional  quantity  of  the  acid  is  procured.  To  render  it 
quite  pure,  it  should  be  dissolved  in  hot  water,  and  neutralized  by  carbonate  of 
polassa.  As  the  liquid  cools,  carbazotate  of  potassa  crystallizes,  and  may  be  puri- 
fied by  repeated  crystallization.  The  acid  may  be  precipitated  from  this  salt  by 
sulphuric  acid. 

Properties,  1701.  Carbazotic  acid  is  sparingly  soluble  in  cold  water  ; but  it  is 
dissolved  much  more  freely  by  the  aid  of  heat,  and  on  cooling  yields 
brilliant  crystalline  plates  of  a yellow  colour.  Ether  and  alcohol 
dissolve  it  readily.  It  is  fused  and  volatilized  by  heat  without  de- 
composition ; but  when  suddenly  exposed  to  a strong  heat,  it  inflames 
without  explosion,  and  burns  with  a yellow  flame,  with  a residue  of 
charcoal.  Its  solution  has  a bright  yellow  colour,  reddens  litmus 
paper,  is  extremely  bitter,  and  acts  like  a strong  acid  on  metallic  ox- 
ides. It  is  said  to  be  poisonous.! 

Salts  of.  1702.  The  salts  of  carbazotic  acid  are  for  the  most  part  crystal- 


* From  the  analysis  by  Dumas,  Thomson  considers  it  as  merely  indigo,  containing 
five  times  as  much  oxygen  as  that  pigment  does.  T.  142. 
t Jour,  of  Sci.  ii.  210. 


Pectic  Acid . 


393 


lizable,  of  a yellow  colour,  and  brilliant  lustre.  They  have  the  pro-  Sect,  n. 
perty,  when  rapidly  heated,  either  of  detonating  like  fulminating 
silver,  or  of  burning  rapidly  with  scintillations.  The  sparing  solu- 
bility of  carbazotate  of  potassa  is  the  cause  of  carbazotic  acid  being 
used  as  a test  of  that  alkali. 

1703.  Carbazotic  acid  is  generated  by  the  action  of  nitric  acid  on 
many  substances,  both  animal  and  vegetable,  especially  on  those 
which  contain  nitrogen.  The  bitter  principle, . formed  with  nitric 
acid  and  silk  by  Welter,  is  carbazotic  acid. 

Acids  Imperfectly  Examined. 

1704.  Pectic  Acid.  CaH7O10,  = 153  eq.  Braconnot  has  given  this  Pectic  acid, 
name*  to  a principle  found  in  several  plants  which  has  the  property 

of  being  coagulated  by  alcohol,  metallic  solutions,  the  acids,  &c.  It 
appears  to  be  the  same  substance  previously  discovered  by  Torrey  in 
the  Tuckahoe,  Sclerotium  giganteum,i  a fungus  common  in  the 
sandy  barrens  of  the  southern  states,  and  to  which  he  gave  the  name 
Sclerotin.  It  is  readily  soluble  in  a solution  of  caustic  potassa,  and 
this  solution  is  gelatinized  by  almost  every  known  body. 

1705.  Braconnot’s  process  for  obtaining  this  substance  is  as  fol-ta?^d°  " 
lows : 

If  roots  containing  starch  be  operated  upon,  such  as  those  of  celery  and  carrot, 
they  are  to  be  reduced  to  pulp  by  rasping,  the  juice  expressed,  the  residue  boiled 
in  water,  slightly  acidified  with  hydrochloric  acid,  then  washed,  and  afterwards 
heated  with  a very  dilute  solution  of  potassa  or  soda.  A thick  mucilaginous 
liquid  results,  slightly  alkaline,  from  which  hydrochloric  acid  separates  the  acid  in 
the  form  of  an  abundant  jelly,  which  should  then  be  well  washed. 

1706.  It  forms  a very  soluble  salt  with  potassa,  which  may  be  ob-  Union  with 
tained  in  the  state  of  a transparent  jelly,  by  adding  weak  alcohol,  p as 
which  removes  the  excess  of  alkali  and  colouring  matter,  if  there  be 

any  present.  This  jelly  washed  on  a cloth  with  alcoholized  water, 
pressed  and  dried,  swells  and  dissolves  in  water,  and  leaves  upon 
evaporation  a transparent  mass,  resembling  gum  arabic.  Its  taste  is 
insipid. 

1707.  In  consequence  of  the  property  which  this  acid  has  of  gela-  Use. 
tinizing  large  quantities  of  water,  it  has  been  proposed  as  a means  of 
preparing  jellies. 

Boil  a little  pectic  acid  in  the  quantity  of  water  which  is  to  be  converted  into 
jelly ; dissolve  in  the  water  a sufficient  quantity  of  sugar  previously  seasoned  by 
being  rubbed  over  the  skin  of  an  orange,  or  by  any  other  wished  for  seasoning, 
or  add  to  the  water  a little  alcohol  previously  seasoned  In  either  case  the  whole 
assumes  the  form  of  a jelly,  the  flavour  of  which  will  of  course  depend  upon  the 
nature  of  the  seasoning  employed. 

1708.  There  is  a substance  in  many  acid  fruits,  as  currants  and  Pectin, 
gooseberries,  which  gelatinizes.  It  has  very  intimate  connexion 
with  pectic  acid,  being  instantly  converted  into  that  acid  by  the 
smallest  quantity  of  a fixed  alkali.  This  substance  has  been  distin- 
guished by  Braconnot,  by  the  name  of  pectin. 

1709.  It  may  be  obtained  from  all  fruits  by  means  of  alcohol.  Process. 

Mix  together  the  clear  expressed  juice  of  currants,  with  the  equally  clear  juice 

* From  TtexTLQ  coagulum.  Ann.  de  Chim.  xxviii.  173,  and  Bost.  Jour.  iii.  132. 

t Torrey’s  analysis  of  the  Tuckahoe  was  published  in  the  N.  Y*  Med.  Rep.  1820. 

50 


394 


Chap.  VI. 


Cieuic 

acid. 


Properties. 


Apocrenic 

acid. 


In  waters. 


Compound 

acids, 

Two  sets. 


Althionic 

acid. 


Vegetable  Acids. 

of  sour  cherries.  Pectin  falls  down.  Decant  off  the  liquid,  and  wash  the  pectin 
with  water,  as  long  as  the  liquid  abstracts  any  colour/ 

The  analysis  of  pectic  acid  by  Regnault  gave,  carbon  42.71,  hy- 
drogen 4.73,  oxygen  52.56. t 

1710.  Crenic  Acid , 108.1  (T.)»  was  discovered  by  Berzelius  in 
1832,  in  the  water  of  Porla  well,  in  Sweden,  to  which  it  imparted  a 
yellow  colour  and  disagreeable  taste.  On  exposure  to  the  air,  an 
ochrey  sediment  was  deposited  which  consisted  chiefly  of  crenated 
peroxide  of  iron.§ 

1711.  Crenic  acid  is  yellow  and  transparent.  It  has  no  odour, 
but  a sharp  followed  by  an  astringent  taste.  When  in  solution  the 
latter  only  can  be  perceived.  When  the  solution  is  exposed  to  the 
air,  it  becomes  brown,  and  apocrenic  acid  is  formed. 

1712.  It  is  very  soluble  in  water  and  alcohol.  Its  salts  resemble 
extracts,  and  are  insoluble  in  absolute  alcohol,  but  become  more  and 
more  soluble  as  water  is  added.  They  become  rapidly  brown  in  the 
air,  and  apocrenates  are  formed. 

1713.  Crenic  acid  dissolves  in  nitric  acid  without  change.  Its 
salts  are  termed  crenates.  They  resemble  extracts  in  appearance, 
and  are  incapable  of  crystallizing. 

1714.  Apocrenic  Acid.  132.  (T.)«  This  acid  was  obtained  by  di- 
gesting the  ochre  from  Porla  well  with  potassa,  to  extract  the  crenic 
acid,  and  then  precipitating  the  acid  by  means  of  acetate  of  copper. 
The  apocrenate  of  copper  falls,  from  which  the  acid  is  separated  by 
the  action  of  hydrosulphuric  acid  gas,  absolute  alcohol  and  potassa. 

1715.  Apocrenic  acid  is  brown,  and  resembles  a vegetable  ex- 
tract. It  is  but  slightly  soluble  in  water,  from  which  it  is  precipi- 
tated by  sal  ammoniac. 

1716.  These  acids  are  supposed  by  Berzelius  to  occur  frequently 
in  water,  and  he  is  of  opinion  that  the  substances  so  often  described 
as  existing  in  mineral  waters,  and  which  have  been  distinguished  by 
the  name  of  extractive,  in  reality  consist  of  these  acids.  He  thinks 
too  that  they  exist  abundantly  in  bog  iron-ore. 

Compound  Acids. 

1117.  The  compound  acids  consist  of  a vegetable  principle,  united 
to  a strong  mineral  or  vegetable  acid.  They  have  been  divided  by 
Thomson  into  two  sets.  The  first  set  consists  of  two  atoms  of  an 
acid,  combined  with  one  atom  of  abase,  which  may  be  driven  ofFby 
a stronger  base.  They  are,  strictly  speaking,  not  acids,  but  acidu- 
lous or  super-salts.  The  second  set  contains  hyposulphuric  acid, 
combined  with  an  organic  substance,  not  acting  the  part  of  a base, 
and  not  capable  of  being  expelled  by  a stronger  base. 

1718.  Althionic  Acid.W  2(S03)+C4H50-{-H0,  126  eq.  This  nam  j 
is  given  by  Magnus  to  what  was  formerly  called  sulphovinic  acid. 
It  is  formed  by  the  action  of  strong  sulphuric  acid  and  alcohol,  and 


* Jour,  dc  Phar.  xx.  467.  For  other  acids  of  this  group  see  Thomson,  Chem.  Inorg. 
Bodies , ii.  and  Org.  Bodies,  146. 
t Jour,  de  Phar.  xxiv.  201.  t From  xqtjvj]  a fountain. 

S For  details  of  the  analysis  see  T.  148.  ||  From  Osiov,  sulphur  and  alcohol. 


Formo-benzoilic  Acid. 


395 


plays  an  important  part  in  the  formation  of  ether.  When  the  ingre-  Sect.  11. 
dients  for  forming  ether  are  mixed,  and  before  heat  is  applied,  much 
of  the  acid  exists  in  the  state  of  this  acid,  and  may  be  separated  by 
neutralizing  the  mixture  with  carbonate  of  baryta,  when  an  althio- 
nate  of  baryta  is  formed  which  may  be  obtained  in  crystals. 

1719.  From  the  experiments  of  Magnus  it  seems  that  when  equal  Exp®ri"^ 
weights  of  concentrated  sulphuric  acid  and  absolute  alcohol  are  mixed,  Magnus, 
one  half  of  the  acid  deprives  the  other  half  of  all  its  water,  while 
every  two  atoms  of  the  anhydrous  acid  thus  formed  unites  with  C4 
H50+H0  (or  alcohol).  It  is  considered  by  Thomson  as  a bisalt,  or 

a bisulphate  of  ether.*  It  forms  with  bases,  althionates.f 

1720.  Ethionic  Acid.  S^-j-C^O-f-HOT  This  is  one  of  the^jonic 
compound  acids,  containing  an  acid  combined  with  an  organic  sub- 
stance, not  acting  the  part  of  a base  and  not  capable  of  being  expelled 

by  a stronger  base.  It  was  obtained  by  Sertuerner  by  the  action  of 
sulphuric  acid  and  alcohol.^  Sulpho- 

1721.  Sulpho-naplithalic  Acid.  S205+C2oH7,  — 199.024  eq.  Dis-  naphthalic 

covered  by  Faraday  in  1826.  acid> 

It  is  made  by  melting  naphthaline  with  half  its  weight  of  strong  sulphuric  acid,  Process, 
when  a red-coloured  liquid  is  formed,  which  becomes  a crystalline  solid  in  cool- 
ing. The  mass  is  soluble  in  water,  and  the  solution  contains  a mixture  of  sul- 
phuric and  sulphonaphthalic  acids.  On  neutralizing  with  carbonate  of  baryta,  the 
insoluble  sulphate  subsides,  while  the  soluble  sulphonaphthalate  remains  in  solu- 
tion ; and  on  decomposing  this  salt  by  a quantity  of  sulphuric  acid  precisely  suf- 
ficient for  precipitating  the  baryta,  pure  sulphonaphthalic  acid  is  obtained, 

1722.  The  aqueous  solution  of  the  acid,  as  thus  formed,  reddens  Properties, 
litmus  paper  powerfully,  and  has  a bitter  acid  taste.  On  concentrat- 
ing by  heat,  the  liquid  at  last  acquires  a brown  tint,  and  if  then  taken 

from  the  fire  becomes  solid  as  it  cools.  If  the  concentration  is  effected 
by  means  of  sulphuric  acid  in  an  exhausted  receiver,  the  acid  becomes 
a soft  white  solid,  apparently  dry,  and  at  length  hard  and  brittle. 

Sulphonapthalic  acid  is  readily  soluble  in  water  and  alcohol,  and  F°Jms 
is  also  dissolved  by  oil  of  turpentine  and  olive  oil,  in  proportions  de-  sa  s" 
pendent  on  the  quantity  of  water  which  it  contains.  By  the  aid  of 
heat  it  unites  with  naphthaline.  It  combines  with  alkaline  bases,  and 
forms  neutral  salts,  which  are  called  sulpkonaphtholates.  All  these 
salts  are  soluble  in  water,  and  most  of  them  in  alcohol,  and  .when- 
exposed:  to  heat  in  the  open  air,  take  fire.  j| 

1723.  Sulpho-indigotic  and  Hypo-sulpho-indigotic  Acids  are  ob-  Other  acids 

tained  from  indigo  dissolved  in  sulphuric  acid.  ™ in  1= 

Sulpho-indigotate  of  Potassa  has  received  various  names,  ns  pre- 
cipitated indigo , soluble  indigo , and  carmine  of  indigo.  Crum  showed 
that  it  was  a compound  of  indigo  and  sulphate  of  potassa.  He  gave 
the  name  of  cerulin,  from  its  blue  colour,  to  the  soluble  indigo  Cerulin. 
contained  in  it,  and  that  of  ceruleo-sulphates  to  the  salts  consisting  of 
this  substance  united  with  sulphates.- 

1724.  Formo-benzoilic  acid  may  be  obtained  by  mixing  the  water  ^e°n™il*ic 
distilled  off  bitter  almonds  with  hydrochloric  acid,  and  evaporating.  acid. 


* Organic  Bodies , 169. 

t Phosphovinic  Acid  is  obtained  by  distilling  a mixture  of  phosphoric  acid  and  Phosphovini® 
alcohol.  t Liebig.  % Ann.  de  Chim.  et  Phys.  xiii.  62. 

It  The  sulpho-naphthalate  of  baryta  has  been  found  by  Berzelius  to  be  a mixture  of 
two  salts  difficult  to  separate  ; one  containing  sulpho-naphthalic  and  the  other  hypo- 
sulpho-naphthalic  acid  2(S03)-fCnH45. 


396 


Chap.  VI. 


Composi- 

tion. 


Cyanogen, 
a com- 
pound rad- 
ical. 


Mellon, 


Obtained. 


Melamin, 


Cyanogen  and  its  Compounds. 

It  remains  in  crystalline  masses  mixed  with  sal  ammoniac,  from 
which  it  is  freed  by  ether,  which  dissolves  the  new  acid.  It  is  white, 
very  soluble  in  water,  has  a strong  acid  taste,  neutralizes  bases  and 
forms  salts  with  oxides  of  silver  and  copper.  It  is  decomposed  by 
heat,  leaving  charcoal,  and  giving  out  the  odour  of  peach  blossoms. 


Thomson  considers  it  a compound  of 
1 atom  formic  acid 
1 “ hydret  of  benzoil 

- 

c 2h  o3 

CuH6  O2 

C1&H7  O5 

The  hydrocyanic  acid  and  water  of  the  bitter  almonds  is  decomposed  into  for- 
mic acid  and  ammonia,  for 

1 atom  of  hydrocyanic  acid  - - C^II  N 

3 “ water  - - - H3  O3 

1 “ formic  acid  - 

I “ ammonia 

* 

c2  h4  no3 

C2  H 03 
h3  n 

CalLNOa 

This  constitutes  an  acid  formed  by  the  combination  of  two  organic  bodies  pos- 
sessing the  characters  of  acids,  and  capable  of  being  formed  at  pleasure.* 


Section  III.  Cyanogen  and  its  Compounds. 

1725.  Cyanogen  is  considered  by  Liebig  as  a compound  radical, 
and  as  such  uniting  with  oxygen,  hydrogen,  and  most  other  non- 
metallic  elements,  and  also  with  the  metals ; many  of  the  latter  being 
similar  to  haloid  salts,  while  others  possess  a very  different  character. 

In  describing  the  compounds  of  cyanogen,!  it  will  be  necessary  to 
employ  new  terms,  and  refer  to  several  substances  which  have  not 
been  described  in  the  foregoing  pages,  a brief  account  of  them  is 
therefore  introduced  in  this  place. 

1726.  Mellon , C6N4,  eq.  =93.32, t is  a yellow  powder,  insoluble  in 
water,  alcohol,  and  dilute  hydrochloric  and  sulphuric  acids,  but  solu- 
ble with  decomposition  in  nitric  acid  and  the  caustic  fixed  alkalies, 
decomposable  by  a strong  heat,  into  three  vols.  cyanogen,  and  one 
vol.  nitrogen  gas.  It  unites  with  potassium  forming,  mellonuret  of 
potassium,  with  hydrogen  forming  hydromellonic  acid.$  Discovered 
by  Liebig,  and  considered  by  him  a compound  radical. 

It  is  obtained  when  dry  sulpho-cyanogen  is  heated  in  a retort  to 
redness,  the  products  of  the  decomposition  being  sulphuret  of  carbon, 
sulphur  and  inellou. 

1727.  Melamin , C6N6H6,  eq.  =121.62,  is  a saline  base  discovered 
by  Liebig,  being  a product  of  the  decomposition  of  melam  (1729)  by 
alkalies  and  dilute  acids.  It  crystallizes  in  colourless  or  slightly  yellow 
rhombic  octohedrons,  transparent,  anhydrous,  sparingly  soluble  in 


* T.  Organic  Bodies,  206. 

t These  compounds  constitute  the  Second  Series  of  Liebig.  For  details,  see  Thom- 
son, Org.  Bodies , 768,  and  Liebig,  Org.  Chem.  755. 

t The  formulas  are  those  of  Liebig. 

§ By  dissolving  mellonuret  of  potassium  in  boiling  water  and  adding  hydrochloric, 
sulphuric,  or  nitric  acid,  hydromellonic  acid  is  obtained.  It  is  decomposed  by  metal- 
lic oxides.  See  L.  796. 


Jlmmdin. 


397 


cold  but  pretty  freely  in  boiling  water,  insoluble  in  alcohol  and  ether.  Sect,  hi. 
It  fuses  when  heated,  and  sublimes,  partially  decomposed  into  mellon 
and  ammonia.  Decomposed  by  concentrated  nitric  acid  and  sulphu- 
ric acid  with  the  aid  of  heat  into  ammonia  and  ammelid  or  ammelin  ; 
fused  with  hydrate  of  potassa,  the  elements  of  3 eq.  of  water  add 
themselves  to  its  constituents  and  form  6 eq.  of  ammonia,  which  are 
evolved,  and  3 eq.  cyanate  of  potassa  are  left. 

1728.  Melamin  combines  with  dilute  acids  to  crystallizable  salts,  Combina- 
all  of  which  have  an  acid  reaction,  excepting  the  double  salts.  The 
acetate  and  formate  of  melamin  are  very  soluble  ; it  precipitates 
magnesia  from  hot  solutions  of  its  salts,  owing  to  the  formation  of  a 
double  salt.  Melamin  combines  directly  with  the  anhydrous  hydra- 

cids,  all  its  salts  with  the  oxacids  correspond  to  the  ammoniacal  salt 
in  containing  an  equiv.  of  water,  without  which  they  cannot  exist; 
it  forms  double  basic  salts  in  which  this  equiv.  of  water  is  replaced 
by  a metallic  oxide. 

1729.  Melam.  C12NnH9,  eq.  = 238.09.  This  product  of  the  de-  Melam. 
composition  of  sulphocyanuret  of  ammonium,  was  also  discovered  by 
Liebig.  When  the  sulphocyanuret  of  ammonium,  or  a mixture  of 

two  parts  of  sal  ammoniac  and  one  of  sulphocyanuret  of  potassium 
are  heated  to  the  point  of  fusion  of  the  latter,  the  sulphocyanuret  of 
ammonium  is  decomposed  into  three  gaseous  and  one  solid  product. 

The  former  are  ammonia,  hydrosulphuric  acid,  and  the  sulphuret  of 
carbon ; the  latter  is  melam,  which  is  left  in  the  retort  mixed  with 
chloride  of  potassium,  and  is  separated  by  washing  with  water. 

1730.  It  is  a white  powder,  insoluble  in  water,  alcohol  and  ether ; Properties, 
but  dissolved  by  hot  potassa,  a part  being  decomposed,  but  another 
portion  is  deposited  again  unchanged  as  the  solution  cools.  It  is  also 
soluble  in  hot  concentrated  sulphuric  and  nitric  acids,  from  which  alco- 
hol and  water  throw  down  ammelid.  If  the  solution  in  these  acids  Solutions 
be  boiled,  it  is  completely  converted  into  cyanuric  acid  and  ammonia  ; ?onverted 

I eq.  melam  and  12  eq.  water,  contain  the  elements  of  2 eq.  of  cya-ric  acid, 
nuric  acid  and  5 eq.  ammonia.  It  is  dissolved  in  hydrochloric  and 
dilute  nitric  acids  and  potassa  with  the  formation  of  ammelin  and 
melamin  ; fused  with  hydrate  of  potassa,  ammonia  is  evolved,  and 
cyanate  of  potassa  produced  ; and  with  potassium  the  mellonuret  of 
potassium  is  formed.  When  heated,  it  decomposes  into  mellon  and 
ammonia. 

1731.  On  heating  8 eq.  sulphocyanuret  of  ammonium,  they  are  Explana- 
decomposed  into  1 eq.  melam,  10  eq.  ammonia,  4 eq.  sulphuret  oftlon* 
carbon,  and  8 eq.  of  hydrosulphuric  acid  ; 1 eq.  of  melam,  on  being 

fused  with  6 eq.  of  hydrate  of  potassa,  give  rise,  by  the  addition  of 
the  elements  of  6 eq.  water,  to  6 eq.  cyanate  potassa  and  5 eq.  am- 
monia. By  long  application  of  heat  to  melam  in  caustic  potassa,  it  is 
decomposed,  together  with  2 eq.  of  water,  into  1 eq.  melamin  and  1 
eq.  ammelin.  Melam  is  converted  into  ammelid  by  the  addition  of 
the  elements  of  6 eq.  water,  which  form  1 eq.  ammelid  and  2 eq. 
ammonia. 

1732.  Ammelin.  C6N5H502,  eq.  =128.47.  A saline  base,  disco- Ammelin, 
vered  by  Liebig.  A product  of  the  decomposition  of  melam  and  mela- 
min by  acids  and  alkalies.  It  is  precipitated  from  the  alkaline  solution 

from  which  melamin  is  deposited,  by  neutralization  with  acetic  acid. 


398 


Chap.  Vf. 


Forms 

salts. 


Nitrate. 


Ammelid. 


Theory  of 
the  compo 
sition  of 
melamin, 
&c. 


Explana- 

tion. 


Cyanuric 
acid,  Ate. 
compared. 


Cyanic 

acid. 


Cyanogen  and  Oxygen . 

It  is  white,  insoluble  in  alcohol  and  ether,  soluble  in  caustic  alkalies, 
yields  by  distillation  a crystalline  sublimate  and  ammonia,  with  a resi- 
due of  pure  mellon.  By  long  boiling  in  dilute  acids,  or  on  being 
dissolved  in  concentrated  sulphuric  acid,  it  is  decomposed  by  the  ad- 
dition of  1 eq.  of  water,  into  ammonia  and  ammelid.  By  fusion 
with  caustic  potassa  1 eq.  of  water  is  decomposed,  and  it  is  converted 
into  ammonia  and  cyanate  of  potassa. 

1733.  Ammelin  is  a weak  salifiable  base,  and  forms  only  with  the 
strong,  and  not  with  the  organic  acids,  crystallizable  salts,  which 
have  an  acid  reaction,  and  are  partially  decomposed  by  water  with 
the  deposition  of  ammelin.  The  salts  of  ammelin  with  the  oxacids 
contain,  like  the  ammonia  salts,  1 eq  of  water,  without  which  they 
cannot  exist;  the  double  salts  are  anhydrous. 

1734.  Nitrate  of  ammelin  crystallizes  in  large  broad  plates,  or  in 
long  quadrangular  prisms.  When  heated  it  fuses  and  ammelid  is 
left,  nitric  acid  and  the  products  of  the  decomposition  of  nitrate  of 
ammonia  are  evolved. 

1735.  Ammelid.  C^NyHaOc,  eq.  =257.79.  A product  of  the  de- 
composition of  melam,  melamin,  and  ammelin  by  concentrated  acids. 
It  is  a white  powder,  insoluble  in  water,  alcohol,  and  ether,  but  soluble 
in  alkalies  and  strong  acids  ; by  continued  boiling  in  dilute  nitric  or 
sulphuric  acid  it  is  decomposed  into  cyanuric  acid  and  ammonia,  l. 

1736.  Liebig  has  given  the  following  explanation  of  the  basic 
qualities  of  melamin,  ammelin,  and  ammelid,  and  of  their  connexion 
with  ammelid  and  cyanuric  acid.  It  is  assumed  that  these  substances 
contain  the  same  radical  as  cyanuric  acid,  together  with  a com- 
pound of  nitrogen  and  hydrogen,  which  is  composed  of  equal 
vols.  of  these  elements,  and  which  are  supposed  to  be  denoted  by  the 
symbol  2M=HN ; the  compounds  may  then  be  represented  in  the 
following  form : 

Cyanuric  acid  - - - Cy3  Oj  -+-  H3 

Melamin  - - - Cys  Me  + H3 

Ammelin  ....  Cy3  M4  O*  + H3 

Ammelid  - Cy3  M3  O3  H3 

Cyanuric  acid  - - - Cy  3 O3  O3  + H3 

1737.  The  cyanuric  acid  is,  as  may  be  seen,  both  the  commence- 

ment and  termination  of  the  series  ; in  melamin,  the  6 eq.  of  oxygen 
are  replaced  by  6M(N3H3),  and  in  ammelin  4 eq.  by  4M;  both  of 
them  are  saline  bases.  The  ammelid  has  no  basic  properties,  and  in 
it  one  half  of  the  oxygen  of  the  cyanuric  acid  is  replaced  by  3M,  and 
by  the  further  removal  of  all  M cyanuric  acid  is  again  produced. 
The  basic  properties  of  these  bodies  decrease  as  the  quantity  of  oxy- 
gen which  combines  with  the  radical  is  increased. 

173?.  The  cyanuric  acid  may  be  compared  with  the  phosphoric 
acid,  and  melamin  with  phosphuretted  hydrogen  or  ammonia  ; am- 
melin and  melamin  enter  into  direct  combination  with  the  hydracids 
and  without  the  intervention  of  water,  but  with  the  oxacids  only  by 
the  intervention  of  1 eq.  of  water,  which  must  be  in  the  same  state 
of  combination  as  in  the  ammoniacal  salts.  L.  803. 

Cyanogen  and  Oxygen. 

1739.  Cyanic  Acid.  CyO,  26.39  1 eq.  cy.  + 8 1 eq.  oxy.  = 34.39 
equiv.  This  acid  was  discovered  by  Wohler,  and  is  formed  when 


399 


Cyanaies  of  Ammonia. 

■cyanogen  is  transmitted  over  carbonate  of  potassa  at  a red  heat,  or  Sect,  nr. 
into  an  alkaline  solution ; by  exposing  compounds  of  cyanogen  at  a 
red  heat  to  the  action  of  the  air,  of  nitre,  or  of  peroxide  of  manga- 
nese ; by  fusing  ammelin,  melamin,  or  ammelid  with  hydrate  of 
potassa;  it  is  a frequent  product  of  the  decomposition  of  compounds 
of  nitrogen.  It  is  not  known  in  the  anhydrous  state. 

Obtained  as  hydrate,  by  distilling  dry  cyanuric  acid  or  cyamelide*  Obtained, 
in  a retort,  when  the  latter  is  converted  into  hydrate  of  cyanic  acid, 
which  must  be  collected  in  a receiver  well  cooled  by  ice. 

1740.  A clear  transparent  fluid  of  a strong  penetrating  odour,  Properties, 
similar  to  that  of  acetic  or  formic  acid,  exceedingly  volatile,  and 
causes  blisters  on  the  skin,  which  are  accompanied  by  great  pain. 

Mixes  readily  with  water.  Decomposes  with  the  production  of  great 
heat  shortly  after  its  formation  into  a white  solid  of  the  same  com- 
position per  cent,  (cyamelide)  ;t  its  aqueous  solution  reddens  vege- 
table colours  strongly ; it  decomposes  in  the  course  of  a few  minutes, 
together  with  2 eq.  of  water,  into  bicarbonate  of  ammonia ; 

Hydrated  cyanic  acid  = C2NO+HO  >_  C 2 eq.  carb.  acid  . =2C02 

Two  eq.  water  . = 2H0  } — ( 1 eq.  ammonia  . = NH3 

C2N  H3O4  C2NH3O4 

1741.  This  acid  forms  only  one  series  of  salts  with  the  bases ; Forms 
they  are  readily  recognised  by  the  peculiar  decomposition  produced  sa  ls" 
by  dilute  mineral  acids.  A few  moments  after  mixing  the  salt  with 

the  acid,  a rapid  effervescence,  accompanied  by  the  strong  penetrat- 
ing odour  of  cyanic  acid,  is  observed,  and  the  solution  by  being  mixed 
with  hydrate  of  lime  evolves  ammonia  abundantly,  which  previous 
to  the  decomposition  cannot  be  detected.  Its  salts  with  the  alkaline 
bases  and  with  ammonia  are  soluble,  the  others  are  insoluble  ^ the 
former,  with  the  exception  of  the  ammoniacal  salt,  are  decomposed, 
when  their  solutions  are  boiled,  into  ammonia  and  carbonates. 

1742.  Cyanates  of  Ammonia . Cyanic  acid  forms  with  ammonia  Cyanatesof 
two  compounds,  one  of  which  is  particularly  remarkable  from  its  ammonia, 
identity  with  urea. 

1.  Basic  Cyanate  of  Ammonia.  When  dry  ammoniacal  gas  and  the  Basic  cya^ 
vapour  of  hydrated  cyanic  acid  are  simultaneously  conducted  into  anateofam- 
dry  vessel,  they  unite,  forming  a white  woolly  crystalline  compound,  monm> 
which  contains  more  ammonia  than  corresponds  to  the  constitution 

of  a neutral  cyanate.  It  is  similar  in  all  its  properties  to  any  other 
salt  of  cyanic  acid ; treated  with  an  acid  it  is  decomposed  with  effer- 
vescence, and  alkalies  effect  the  evolution  of  ammonia  ; but  if  on  the 
contrary  it  be  gently  warmed,  whether  dry  or  in  solution,  or  if  it  be 
left  for  some  time  exposed  to  the  air,  ammonia  is  given  off,  it  loses 
all  the  above-mentioned  properties,  and  is  converted  into  urea. 

2.  Anomalous  Cyanate  of  Ammonia  ; XJrea.  Discovered  by  Four- Urea, 
croy  and  Vauquelin  in  urine,  by  Wohler  as  the  first  organic  compound 


* Insoluble  Cyanuric  Add  (1767). 

+ This  decomposition  with  water  is  the  cause  of  the  impossibility  of  obtaining  the  free 
acid  from  the  aqueous  solutions  of  its  salts  by  the  action  of  a stronger  acid,  although 
a small  quantity,  as  may  readily  be  recognised  by  the  peculiar  odour  which  accompa- 
nies the  carbonic  acid  evolved,  does  escape. 


400 


Chap.  VI. 

Process, 


Another, 


Properties. 


Com- 

pounds, 

Decom- 

posed, 


Caution. 


Cyanogen  and  its  Compounds. 

artificially  produced.  It  is  a constituent  of  uric  acid,  and  is  con- 
tained in  the  urine  in  combination  with  lactic  acid.*  It  is  obtained, 

1743.  By  mixing  fresh  urine  evaporated  to  the  consistence  of  a syrup  at  a 
gentle  heat,  which  should  never  reach  that  of  ebullition,  when  quite  cold,  with 
its  own  volume  of  colourless  nitric  acid  of  sp.  gr.  = 1.42.  If  the  evaporation  has 
been  carried  sufficiently  far,  the  whole  will  form  a thick  crystalline  mass;  to  en- 
sure this,  a small  portion  of  the  urine  should  be  tried  from  time'  to  time.  The 
crystalline  mass  consists  of  a compound  of  nitric  acid  and  urea,  which  is  sparingly 
soluble  in  nitric  acid.t 

The  impure  crystals  of  nitrate  of  urea  are  to  be  carefully  washed 
with  dilute  nitric  acid,  strongly  pressed  between  folds  of  bibulous 
paper,  dried  upon  a porous  tile,  and  redissolved  in  warm  water ; the 
solution,  after  being  freed  of  its  colour  by  recently  prepared  charcoal, 
is  evaporated  to  crystallize. 

A solution  of  the  colourless  crystals  of  the  nitrate  of  urea  is  treated  with  car- 
bonate of  baryta  until  it  is  rendered  perfectly  neutral ; on  evaporating,  crystals  of 
nitrate  of  baryta,  and  then  of  urea,  will  be  obtained.  The  crystals  of  the  latter, 
by  being  redissolved  in  a little  cold  water,  are  freed  from  the  last  portions  of  the 
nitrate  of  baryta  ; the  solution  in  alcohol  gives  crystals  of  pure  urea.t 

1744.  Instead  of  using  nitric  acid,  the  concentrated  urine  may  be 
added  to  a boiling  saturated  solution  of  oxalic  acid,  when  the  spar- 
ingly soluble  oxalate  of  urea  falls,  which,  after  being  deprived  of  its 
colour  by  charcoal,  may  be  decomposed  into  the  insoluble  oxalate  of 
lime  and  pure  urea,  by  being  digested  with  pounded  chalM  It  can 
also  be  prepared  by  the  decomposition  of  the  cyanate  of  oxide  of  sil- 
ver by  sal-ammoniac,  or  of  the  cyanate  of  oxide  of  lead  by  pure  or 
carbonate  of  ammonia. 

1745.  Crystallizes  in  colourless,  transparent,  four-sided,  somewhat 
flattened  prisms  of  the  sp.  gr.  1 35,  is  soluble  in  its  own  weight 
of  cold,  and  in  every  proportion  in  hot  water,  in  4.5  parts  of  cold, 
and  in  2 parts  of  boiling  alcohol : the  aqueous  solution  has  a cooling 
bitter  taste  like  nitre  ; when  pure  it  is  perfectly  permanent  in  the  air, 
is  not  deliquescent,  fuses  at  250°  into  a colourless  liquid,  is  decom- 
posed by  a higher  temperature  into  ammonia,  cyanate  of  ammonia, 
and  dry  solid  cyanuric  acid.  Alkalies  do  not  cause  the  separation  of 
ammonia  in  the  cold. 

1746.  Unites  with  several  acids  without  decomposition  to  crystal- 
lizabie  saline  compounds  : by  evaporating  its  solution  with  nitrate  of 
silver  or  acetate  of  lead  it  is  decomposed  ; the  products  being,  with 
the  first,  nitrate  of  ammonia  and  crystalline  cyanate  of  silver;  with 
the  second,  acetate  of  ammonia  and  carbonate  of  lead.  With  hypo- 
nitrous  acid  it  is  instantly  decomposed  into  nitrogen  and  carbonic 
acid  gases,  which  are  evolved  in  equal  volumes;  with  chlorine  it 
forms  hydrochloric  acid,  nitrogen  and  carbonic  acid.  When  fused 
with  the  hydrated  alkalies,  or  heated  in  concentrated  sulphuric  acid, 
it  is  decomposed  together  with  the  constituents  of  3 eq.  of  water  into 
carbonic  acid  and  ammonia.  Urea  contains  the  elements  of  cyanate 
ofamm  onia  (NH40+C4N0)  ; it  may  also  be  considered,  according 


* Henry. 

t Since  the  urine  contains  metallic  chlorides,  which  with  the  nitric  acid  by  the  aid 
of  heat  are  decomposed,  and  give  rise  to  the  production  of  chlorine  and  nitrous  acid, 
both  of  which  act  powerfully  in  destroying  urea,  all  increase  of  temperature  must  be 
most  carefully  avoided.  t Wohler.  § Berzelius. 


Fulminic  Acid.  401 

to  Dumas,  as  a second  compound  of  carbonic  oxide  and  amide,*  in  Sect,  in. 
which  the  quantity  of  the  latter  is  double  that  in  oxamide  C202-f~ 

2NH2. 

1747.  Nitrate  of  Urea.  This  compound,  when  recently  precipi- Nitrate  of 
tated  from  urine,  appears  in  the  form  of  fine  crystalline  plates  of  a urea* 
brown  colour  and  mother-of-pearl  lustre  ; the  purer  they  are,  the 

more  they  lose  this  appearance  ; a solution  of  pure  urea  treated  with 
nitric  acid  gives  a granular  white  crystalline  precipitate,  which  is 
soluble  in  8 parts  of  cold,  but  more  freely  in  hot  water,  from  which 
it  crystallizes  in  broad,  scarcely  translucent  plates  ; is  sparingly  so- 
luble in  nitric  acid,  with  which  it  may  be  boiled  without  decomposi- 
tion. Is  composed  of  l eq.  of  nitric  acid,  1 of  urea,  and  1 of  water.! 

1748.  Cyanate  of  Potassa.  KOCyO  ; eq.  = 81.54.  By  roasting  Cyanate  of 
at  a red  heat  dry  ferrocyanuret  of  potassium  in  fine  powder  upon  an  potassa“ 
iron  plate,  the  powder  being  constantly  stirred  ; the  cyanuret  of  po- 
tassium contained  in  the  salt  is  thus  converted,  by  absorbing  the  ox- 
ygen of  the  air,  into  cyanate  of  potassa.  As  soon  as  it  is  baked 

into  one  mass,  owing  to  the  fusion  of  the  cyanate  of  potassa  forming, 
it  must  be  reduced  to  a fine  powder  and  digested  in  boiling  alcohol, 
from  which,  as  the  solution  cools,  crystals  of  the  cyanate  are  depo- 
sited. 

A mixture  of  two  parts  of  ferrocyanuret  of  potassium,  and  one  of  peroxide  of  Process, 
manganese,  may  be  treated  in  the  same  way.  This  mixture  may  be  kindled  by  a 
red-hot  body,  when  it  smoulders  away  into  a brown  mass  which  contains  cya- 
nate of  potassa,  carbonate  of  potassa,  and  sesquioxide  of  manganese.  This  salt  may 
also  be  procured  of  great  purity,  but  not  so  economically,  by  fusing  the  hydrate  of 
potassa  in  a silver  vessel,  and  adding  melam,  ammelin,  or  ammelid  in  successive 
portions  as  long  as  they  are  dissolved  ; the  fused  transparent  mass  congeals,  on 
cooling,  to  a pure  crystalline  cyanate  of  potassa. 

1749.  Crystallizes  from  the  alcoholic  solution  in  transparent  an- Properties 
hydrous  plates,  which  closely  resemble  chlorate  of  potassa,  but  by 
exposure  to  a moist  air  are  gradually  converted,  without  any  change 

of  form,  into  bicarbonate  of  potassa,  while  ammonia  is  evolved.  It 
is  dissolved  by  cold  water,  in  which  it  decomposes  into  bicarbonate  of 
potassa  and  ammonia  ; a change  accelerated  by  heat.  Fuses  at  a high 
temperature  without  loss  of  weight  to  a clear  liquid,  which,  upon 
cooling,  forms  an  opaque  crystalline  mass.  If  a concentrated  solu- 
tion be  partially  decomposed  by  acetic  acid,  or  a dilute  mineral  acid, 
the  acid  cyanuret  of  potassa  is  precipitated. 

1750.  Cyanates  of  oxides  of  silver  and  lead , AgOCyO,  and  ^de^of  °f 
PbOCyO,  are  white  anhydrous  salts,  which  are  insoluble  in  water,  silver  and 
and  are  obtained  by  precipitating  the  cyanate  of  potassa  by  a neutral lead' 

salt  of  lead  or  silver.  Both  consist  of  an  eq.  of  acid  and  one  of  me- 
tallic oxide;  the  silver  salt  is  soluble  in  ammonia,  with  which  it 
forms  a white  crystalline  compound,  but  by  heat  the  ammonia  is  Products  of 
again  evolved,  and  the  pure  cyanate  of  silver  remains  ; decomposed  dec<n?- 
by  heat  when  dry,  with  a slight  explosion,  into  cyanic  acid,  carbonic  posulon‘ 
acid,  nitrogen  and  dicyanuret  of  silver. 

1751.  Fulminic  Acid , Cy202;  eq.  = 68.78,  the  constituent  of  the  Fulminie 
fulminating  silver  and  mercury  discovered  by  Howard. 


*This  term  has  been  already  explained  (1563).  “ It  signifies  an  anhydrous  amrao- 

niacal  salt,  deprived  (if  an  expression  apparently  contradictory  may  be  allowed)  of  an 
atom  of  water.”  T.  590.  t Regnault. 

51 


402 


Chap.  Vf. 

Prepara- 

tion. 


Properties. 


Fulmi- 

nates. 


Fulminate 
of  protox- 
ide of  mer- 
cury. 
Process. 


Cyanogen  and  Compounds . 

This  acid  is  formed  when  nitrate  of  silver  or  protoxide  of  mercury, 
with  an  excess  of  nitric  acid,  is  boiled  in  alcohol ; aldehyd*  with  ni- 
tric ether  is  evolved,  and  a white  crystalline  precipitate,  the  fulmi- 
nate of  silver  or  mercury,  is  deposited  from  the  hot  solution.  By 
the  action  of  the  nitric  acid  upon  the  alcohol,  hyponitrous  acid  on 
the  one  hand,  and  aldehyd  and  oxalic  acid  on  the  other,  are  pro- 
duced. The  presence  of  the  oxide  of  silver  or  mercury,  effects  a re- 
action between  two  eq.  of  hyponitrous  acid  and  one  of  ether  in  the 
alcohol,  by  which  they  are  converted  into  water  and  fulminic  acid. 

2 eq.  hyponitrous  acid.  Ether.  Fulminic  acid.  Water. 

N206  + C4H50  = N2C402  + 2HO 

1752.  If  a stream  of  hyponitrous  acid  vapour  be  conducted  into  a 
solution  of  nitrate  of  silver  in  alcohol,  a copious  precipitate  of  fulmi- 
nate of  silver  is  instantly  formed. 

This  is  a bibasic  acid ; it  cannot  be  obtained  in  a free  state  from 
any  of  its  salts,  being  decomposed  at  the  moment  of  its  separation  by 
any  other  acid  into  hydrocyanic  acid  and  a new  product. 

1753.  Fulminates.  The  salts  of  fulminic  acid  contain  either  2 
atoms  of  a fixed  base  (neutral  salts)  or  1 atom  of  a fixed  base  and  1 
atom  of  water  (acid  salts).!  If,  as  Liebig  supposes,  the  salts  are 
considered  as  compounds  of  metals  with  certain  radicals,  which 
arise  from  the  union  of  the  oxygen  of  the  base  with  the  constituents 
of  the  anhydrous  acid  ; when  it  so  happens  that  the  affinity  of  the 
metal  for  the  oxygen  with  which  it  is  united  predominates,  it  is  im- 
possible that  the  radical  should  be  formed,  or,  what  is  the  same  thing, 
that  its  decomposition  must  follow  whenever  an  attempt  is  made  to 
separate  a metallic  oxide,  which  is  easily  reduced,  by  one  holding  its 
oxygen  by  a powerful  affinity. 

1754.  Fulminate  of  Protoxide  of  Mercury , 2Hg0,Cy202 ; eq.  = 
488.78,  discovered  by  Howard,  is  prepared  by  dissolving  1 part  of 
mercury  in  12  parts  of  nitric  acid  of  sp.  gr.  1.36,  and  adding  to  the 
solution  11  parts  of  alcohol  of  80 — 85  per  cent. ; the  mixture  must 
be  heated  in  a water-bath.  The  fluid  soon  enters  into  powerful  che- 
mical action  ; metallic  mercury  is  precipitated,  and  nitric  ether  va- 
pours evolved,  the  latter  carrying  off  along  with  them  a considerable 
portion  of  the  former ; after  a short  time,  hard  opaque  crystals  of 
fulminate  of  mercury  are  deposited.  These  are  carefully  washed 
and  dried  at  common  temperatures  on  paper.  It  is  freed  from  the 
admixture  of  metallic  mercury  by  being  re-dissolved  in  boiling  water, 
from  which  it  is  deposited  in  white  fine  acicular  crystals  of  a soft 
silky  appearance.  Explodes  with  great  violence  when  struck  or 


* Aldehyd,  from  alcohol  dehydratus ; a remarkable  substance  obtained  from  alcohol, 
it  is  a colourless  liquid,  very  volatile,  with  a peculiar  etherial  and  penetrating  odour. 

t The  two  atoms  of  fixed  base  must  either  be  two  atoms  of  the  same  or  of  two  dif- 
ferent metallic  oxides,  which  are  readily  reduced,  (2  eq.  of  CuO,  2 of  HgO,  2 of  AgO, 
or  1 eq.  of  CuO  and  1 eq.  of  AgO,  &c  ) or  1 eq.  of  an  easily  reduced  oxide  with  1 eq. 
of  an  alkali,  (1  eq.  AgO  and  1 eq.  KO  or  BaO,  or  HOZnO,  &c.)  Fulminates  with 
two  atoms  of  a difficultly  reduced  metallic  oxide  cannot  be  obtained.  From  this  it 
follows  that  when  a salt  of  the  first  class, — such,  therefore,  as  contain  2 eq.  of  oxides 
of  silver,  mercury,  or  copper,— are  brought  into  contact  with  an  alkali,  only  one  half 
of  the  metallic  oxide  is  replaced  by  its  equivalent  of  the  alkali ; the  other  half  remains 
in  the  new  compound.  This  remarkable  property  seems  to  indicate  a more  intimate 
connexion  between  the  acid  and  the  oxygen  of  the  metallic  oxide  which  is  combined 
with  it,  than  is  usually  considered  to  exist.  L.  761. 


Cyanuric  Acid.  403 

rubbed  between  two  hard  substances  ; placed  on  a red-hot  coal,  it  Sect,  m. 
burns  with  a slight  explosion  and  a blue  flame. 

1755.  It  is  used  for  firing  percussion  guns  : for  this  purpose,  10  Use. 
parts  of  the  salt  are  reduced  to  a fine  powder  by  rubbing  it  with  a 
wooden  pestle  on  a marble  slab  with  30  parts  of  water  ; and  this, 
when  mixed  with  6 parts  of  nitre,  forms  a paste,  with  which  the  cop- 
per caps  are  filled. 

1756.  Fulminate  of  Silver . 2Ag0-j“Cy202.  Prepared  by  dissolv-  Fulminate 
ing  1 part  of  silver  in  10  of  nitric  acid  of  sp.  gr.  1.36 — 1.38  at  a gen-  of  silver, 
tie  heat,  adding  the  mixture  to  20  parts  of  alcohol  of  85  to  90  per  Process, 
cent.,  and  heating  the  mixture  gently;  as  soon  as  the  fluid  begins  to 

boil,  it  is  removed  from  the  fire,  and  placed  aside  to  cool.  The  solu- 
tion loses  its  transparency,  and  deposits  the  fulminate  of  silver  in 
fine  acicular  crystals  of  a snow-white  colour  and  of  great  lustre ; 
when  washed  and  dried,  their  weight  should  equal  that  of  the 
silver  used. 

1757.  The  fulminate  of  silver  is  sparingly  soluble  in  cold,  but  pr0perties„ 
perfectly  soluble  in  36  parts  of  boiling  water;  is  not  decomposed  by 

nitric  acid  ; more  readily  exploded  than  the  mercurial  salt  by  fric- 
tion, a blow,  or  by  contact  with  concentrated  sulphuric  acid.  Caus- 
tic alkalies  separate  half  the  silver  as  oxide,  chloride  of  barium  or 
potassium,  as  chloride  ; crystalline  salts  with  two  bases  are  obtained, 
from  which  the  acid  fulminate  of  silver  may  be  separated  by  nitric 
acid  ; the  latter  salt  may  be  obtained  in  crystals,  and  is  more  soluble 
than  the  neutral  fulminate  of  silver. 

1758.  Fulminate  of  Copper , 2Cu0,Cy202,  is  prepared  by  digesting  Fulminate 
the  fulminates  of  silver  or  mercury  with  metallic  copper.  It  may  be  of  copper, 
obtained  in  green  crystals,  which  are  very  soluble,  and  explode  with 

a green  flame. 

1759.  Fulminate  of  Zinc  is  obtained,  according  to  E.  Davy,. by  di-  Fulminate 
gesting  the  fulminate  of  mercury  with  metallic  zinc.  Frqm  the  of  zinc, 
solution,  which  no  longer  contains  a trace  of  mercury,  baryta 
precipitates  half  the  zinc,  and  the  fulminate  of  zinc  and'  baryta 

> C«y202  is  obtained  ; from  this  the  baryta,  may  be  precipita- 
ted by  free  sulphuric  acid,  and  the  acid  fulminate  of  zinc  remains 
in  solution,  which  has  been  described  by  E.  Davy  as  pure  fulminic 
acid,  but  the  presence  of  the  zinc  may  be  shown  after  the  decompo- 
sition of  the  fulminic  acid  by  the  sulphuret  of  ammonium  and  the 
known  reagents.1^ 

1760.  Hydro-chloro-cyanic  Acid , is  the  product  of  the  decompose-  pjydro- 
tion  of  fulminate  of  silver  by  hydrochloric  acid.  This  substance  has  chloro-cya* 
a biting  but  sweetish  acid  taste,  does  not  precipitate  silver  salts,  and  moacid- 
is  decomposed  by  heat  into  carbonate  of  ammonia  and  other  new 
products.  It  contains  5 eq.  of  chlorine,  and  its  constitution  is  most 
probably  represented  by  the  formula  C2NCl5-f“H2. 

1761.  Cyanuric  Acid.  Described  by  Scheele  as  pyrouric  acid,  by  Cyanuric 
Serullas  as  cyanure,  but  its  nature  was  first  pointed  out  by  Wohler  acid, 
and  Liebig. 


* On  the  preparation  of  this  acid,  see  Fehling  in  JLond. . and  Edin.  Philos Jour » 
July,  1839. 


404 


Cyanogen  and  Compounds. 


Chap.  VI. 


Process. 


Explaua 

lion. 


Properties, 


Cyanu- 

rates. 


Cyanurate 
of  potassa. 


Cyanurate 
of  silver. 


It  is  a product  of  the  decomposition  of  the  solid  chloride  of  cyano- 
gen by  water,  of  the  soluble  cyanates  by  dilute  acids  (acetic,  &c.),  of 
urea  by  heat,  of  uric  acid  by  the  destructive  distillation,  and  of  me- 
lam,  melamin,  ammelid,  and  ammelin  by  acids. 

It  is  best  prepared  by  dissolving  dry  melam  in  strong  sulphuric  acid,  by  aid  of 
a gentle  heat,  throwing  the  solution  into  20—30  parts  of  water  ; the  mixture  must 
be  kept  for  several  days  at  near  its  boiling  heat,  until  upon  trial  it  no  longer  gives 
a white  precipitate  with  ammonia,  when  the  solution  may  be  evaporated  to  crys- 
tallize ; the  crystals  should  be  purified  by  a second  crystallization.  Or  it  may 
be  made  by  heating  urea  beyond  its  point  of  fusion,  until  it  is  converted  with  the 
evolution  of  ammonia  into  a white  or  grayish-white  dry  mass;  this  must  then  be 
dissolved  in  concentrated  sulphuric  acid,  the  solution  treated  with  nitric  acid 
added  drop  by  drop  until  it  becomes  colourless,  and  then  added  to  an  equal  vo- 
lume of  water  ; when  cold,  crystals  of  pure  cyanuric  acid  are  deposited. 

1762.  By  dissolving  melam  in  strong  sulphuric  acid  it  is  converted 
into  ammelid,  which,  by  being  further  heated,  is  converted  into  am- 
monia and  cyanuric  acid.  Three  atoms  of  urea  contain  the  elements 
of  1 eq.  of  cyanuric  acid,  and  3 eq.  of  ammonia  ; at  a high  tempera- 
ture the  greater  part  of  the  ammonia  is  evolved  as  a gas,  while  a 
small  portion  remains  in  combination  with  the  cyanuric  acid. 

1763.  Colourless,  inodorous,  a slight  taste,  reddens  litmus  feebly, 
sparingly  soluble  in  cold,  but  taken  up  by  24 parts  of  boiling  water;  the 
crystals  from  the  aqueous  solution  contain  21.66  per  cent.  =4  eq. 
water,  which  they  Jose  at  common  temperature  when  exposed  to  the 
air,  but  more  rapidly  when  heated,  and  fall  into  powder.  They  are 
oblique  rhombic  prisms.  The  dry  acid  contains  3 eq.  of  water  ; it 
may  be  obtained  in  crystals  free  from  water  of  crystallization  from  a 
hot  saturated  solution  in  nitric  or  hydrochloric  acid.  The  hydrate 
when  heated  is  converted  into  3 eq.  of  hydrated  cyanic  acid,  the 
constituents  of  which  it  contains.  It  is  soluble  in  the  strongest  acids 
without  decomposition,  but  by  long-continued  boiling  is  converted 
into  ammonia  and  carbonic  acid. 

It  is  a tribasic  acid  ; its  hydrate  is  Cy303-|-3H0 ; eq.  = 130.17. 

1764.  Cyanurates.  The  salts  of  cyanuric  acid  contain  three  atoms 
of  base,  which  are  represented  in  the  hydrate  by  three  atoms  of  wa- 
ter. All  cyanurets  are  decomposed  by  hydrochloric,  nitric  acids, 
& c. ; the  cyanuric  acid  crystallizes  out  of  the  solutions  without  re- 
taining a trace  of  the  metallic  oxide  with  which  it  was  united.  Its 
alkaline  salts  fuse  when  heated,  leaving  a cyanate  of  the  alkali, 
while  cyanate  of  ammonia,  cyanic  and  carbonic  acids,  are  evolved. 

1765.  Cyanurate  of  Potassa.  The  salt  < | -f“Cy303  is  made 

by  neutralizing  a boiling  saturated  solution  of  cyanuric  acid  by  po- 
tassa; it  falls  in  the  form  of  white  brilliant  cubes.  If  these  crystals 
be  dissolved  in  a solution  of  caustic  potassa,  the  addition  of  alcohol 
precipitates  the  cyanurate  of  potassa  with  two  equivalents  of  fixed 

base,  | oj^q  j +Cy303,  in  white  acicular  crystals.  On  being  re- 
dissolved in  water  and  evaporated,  it  is  decomposed  into  free  potassa 
and  the  former  salt. 

1766.  Cyanurate  of  Silver.  If  nitrate  of  silver  be  added  to  either 
of  the  above  salts  of  potassa,  a white  precipitate  is  obtained,  which 
is  cyanurate  of  silver,  with  2 eq.  oxide  of  silver  and  1 eq.  water, 


Hydrocyanic  Acid. 


405 


2A^O  I Cy303;  this  salt  Seated  in  the  dry  state  evolves  hydrated 

cyanic  acid.  But  if  a solution  of  silver  be  added  to  a boiling  solu- 
tion of  cyanurate  of  ammonia,  containing  ammonia  in  excess,  the 
cyanurate  with  3 eq.  of  oxide  of  silver  is  formed,  3Ag0,Cy303 ; it  is 
insoluble  in  water;  very  sparingly  soluble  in  dilute  nitric  acid;  may 
be  heated  to  600°  without  decomposition ; is  white,  is  not  blackened 
by  light,  emits  carbonic  acid  and  nitrogen  gases,  at  a red  heat,  leav- 
ing the  cyanuret  of  silver  as  a residue. 

1767.  Cyamelid , or  Insoluble  Cyanuric  Acid.  Probable  formula 
C202+NH  ; eq.  ==  43.39.  The  hydrate  of  cyanuric  acid,  when 
free  from  water  of  crystallization,  hardens  shortly  after  its  prepara- 
tion into  a white  porcelain-like  body,  which  is  insoluble  in  water, 
dilute  acids,  alcohol,  and  ether  ; but  is  dissolved  with  decomposition 
by  the  caustic  alkalies  ; ammonia  is  evolved,  and  cyanate  and  cya- 
nurate of  the  alkali  formed.  Concentrated  sulphuric  acid  dissolves 
it  with  the  aid  of  heat,  when  with  the  elements  of  2 eq.  water  it  is 
decomposed  into  carbonic  acid  and  ammonia ; submitted  to  the  de- 
structive distillation,  it  is  converted  into  hydrated  cyanic,  a change 
which  is  very  readily  accounted  for,  since  its  composition  is  the  same 
as  that  of  the  hydrated  acid. 


Cyanogen  and  Hydrogen. 

1768.  Hydrocyanic  Acid , Prussic  Acid.  Discovered  by  Scheele  ; 
for  a knowledge  of  its  nature  and  chemical  properties  we  are  in- 
debted to  Gay-Lussac  : it  is  a constituent  of  the  water  distilled  from 
the  leaves  and  blossoms  of  several  stone-fruits  ; is  formed  by  the  de- 
structive distillation  of  many  substances  containing  nitrogen,  by  the 
decomposition  of  formate  of  ammonia  by  heat,  and  of  the  metallic 
cyanurets  by  acids. 

1769.  Anhydrous  Hydrocyanic  Acid.  Fifteen  parts  of  crystalline  ferrocyanuret 
of  potassium  are  distilled  in  a retort,  at  a very  gentle  heat,  with  a mixture  of  9 
parts  of  sulphuric  acid  and  9 parts  of  water,  and  the  products  collected  in  a well- 
cooled  receiver,  containing  5 parts  of  chloride  of  calcium  in  coarse  fragments  : 
the  mixture  of  acid  and  water  should  not  be  used  till  perfectly  cold.  The  distil- 
lation is  stopped  as  soon  as  the  chloride  of  calcium  is  perfectly  covered  by  the 
fluid  collected  in  the  receiver.  It  is  then  poured  off  into  a strong  glass  vessel 
with  a good  stopper.* 

The  ferrocyanuret  of  potassium  contains  the  cyanuret  of  potassium, 
which  is  decomposed  by  the  hydrous  sulphuric,  acid  into  sulphate  of 
potassa  and  hydrocyanic  acid ; the  latter  passes  over  with  a little 
water  into  the  receiver,  but  this  is  absorbed  by  the  chloride  of  calci- 
um. It  can  also  be  prepared  by  decomposing  the  bicyanuret  of  mer- 
cury by  strong  hydrochloric  or  dry  hydrosulphuric  acid  gas.  l.  766. 

The  bicyanuret  may  be  heated  gently  in  a tube  of  about  18  inches  in  length 
and  at  least  half  an  inch  in  diameter  internally,  nearly  filled  with  that  substance, 
and  placed  horizontally,  as  in  Fig.  189. 

the  cut  (Fig.  189).  The  gas  is  *L 
passed  over  until  the  contents  of  ^ 
the  tube  have  become  black; 
none  of  the  gas  escaping  from 
the  other  extremity  of  the  tube, 
till  all  the  bicyanuret  is  decom- 


Sect.  III. 


Cyamelid. 


Prussic 

acid. 


Anhydrous 
Hydrocya- 
nic acid. 
Process, 


Explained. 


Process. 


* Trautwein. 


406 


Chap.  VI. 


Properties. 


Freezing 

point. 

Decom- 
posed by 
light,  &c. 


Action  of 
potassium. 


Hdyrous 
hydrocya- 
nic acid. 
Process. 


Cyanogen  and  Hydrogen. 

posed.  Whenever  the  odour  of  the  gas  is  perceived  at  the  mouth  of  the  receiv* 

' er,  the  tube  a,  connected  with  the  apparatus  in  which  the  gas  is  produced,  is 
withdrawn,  and  the  extremity  of  tne  tube  closed  with  plaster  of  Paris.  It  is 
heated  gently  when  the  lute  has  set,  and  the  hydrocyanic  acid  which  has  been 
formed  is  volatilized  and  condensed  in  a small  receiver  placed  in  a freezing  mix- 
ture. 

1770.  At  common  temperatures,  a clear  limpid  fluid,  very  combus- 
tible, burning  with  a reddish  flame,  of  sp.  gr.  = 0.6969  at  64°.  It 
congeals  at  5°  to  a solid  fibrous  mass,  boils  at  80°,  may  be  mixed  in 
every  proportion  with  water,  ether,  and  alcohol;  the  sp.  gr.  of  the 
vapour  is  0.9476  : scarcely  reddens  litmus  paper.  It  has  a peculiar 
penetrating  odour,  similar  to  that  of  bitter  almonds,  checks  the 
breathing,  and  causes  a flow  of  tears  ; it  possesses  a penetrating 
taste,  which  is  somewhat  burning,  and  strongly  bitter;  its  vapour, 
when  inhaled,  acts  instantly  as  a most  powerful  poison.  The  anti- 
dotes are  ammonia,  as  likewise  chlorine,  which,  however,  must  be 
administered  with  caution. 

1771.  The  congelation  of  the  acid  at  5°  is,  according  to  Schulz, 
owing  to  small  quantities  of  water  ; he  states  the  perfectly  anhy- 
drous acid  as  still  liquid  at — 64°. 

1772.  Decomposes  when  perfectly  pure  with  the  greatest  facility 
under  the  influence  of  light,  with  the  formation  of  a brown  substance 
and  ammonia  ; small  quantities  of  acids  prevent  this  decomposition  ; 
by  concentrated  mineral  acids  it  is  very  rapidly  converted,  together 
with  the  elements  of  water,  into  formic  acid  and  ammonia ; 3 eq.  of 
water  and  l of  hydrocyanic  acid,  a strong  acid  being  present,  suffer 
mutual  decomposition,  and  are  converted  into  ammonia  which  unites 
with  the  acid,  and  into  formic  acid. 

1 eq.  hydrocy.  acid  NC2H  1 _ 5 * e(l-  amm*  N H3 

3 eq.  water  H303  $ — ( 1 eq.  formic  acid  C2H03 

NC2H403  nc2h4o3 

1773.  Potassium  heated  in  the  vapour  of  the  acid  unites  with  the 
cyanogen,  and  liberates  the  hydrogen  ; lime  and  baryta,  when  heated 
in  the  vapour,  also  liberate  hydrogen  and  give  rise  to  cyanates  ; it  is 
decomposed  by  chlorine  with  the  formation  of  hydrochloric  acid  and 
chloride  of  cyanogen. 

1774.  Hydrous  Hydrocyanic  Acid.  CyH,  eq.  27.39.  One  part  of 
bicyanuret  of  mercury  dissolved  in  8 parts  of  water  is  treated  with  a 
stream  of  hydrosulphuric  acid  gas  till  the  latter  is  in  slight  excess  ; 
the  free  hydrosulphuric  acid  removed  by  a little  carbonate  of  lead, 
and  filtered.  The  clear  liquid  contains  T\j  of  anhydrous  hydrocya- 
nic acid.  By  the  decomposition  of  the  bicyanuret  of  mercury  the 
fluid  becomes  black  like  ink,  and  it  frequently  only  becomes  clear 
after  the  addition  of  a small  quantity  of  a free  mineral  acid ; it  con- 
tains too,  very  generally,  small  quantities  of  hydro-sulphocyanic 
acid- 

1775.  It  may  be  prepared  of  the  same  strength  and  perfectly  pure, 
according  to  Geiger, 

By  distilling  4 parts  of  crystallized  ferrocyanuret  of  potassium  with  18  parts  of 
water  and  2 of  strong  sulphuric  acid  ; 20  parts  of  water  are  placed  in  the  receiver, 
and  the  distillation  is  conducted  until  38  parts  have  collected.  The  distillation 
is  best  conducted  in  a chloride  of  calcium  bath,  and  the  vapours  should  be  con- 
densed by  a condensing  apparatus  of  glass.  The  product  is  collected  in  a cylin- 
drical bottle,  which  is  marked  at  the  point  corresponding  to  38  parts. 


Hydrocyanic  Acid. 

1776.  According  to  Clark,  it  may  be  prepared  by  dissolving  1 Sect- In- 
part  of  tartaric  acid  in  40  parts  of  water,  and  adding  2§  parts  of  Clark’s 
pure  cyanuret  of  potassium  in  coarse  fragments  to  the  solution.  The  process, 
fluid  must  be  kept  very  cold,  and  shaken  from  time  to  time  ; this  acid 
contains  3 per  cent,  anhydrous  acid,  and  to  3 grs.  of  bitartrate  of 
potassa  in  the  ounce.^ 

1777.  Magendie  states  that  the  medicinal  hydrocyanic  acid  ispre-  Magenche’s 
pared  by  mixing  1 part  by  volume  of  the  anhydrous  acid  with  6 

parts  of  water  ; or  by  weight,  1 part  of  the  acid  with  8^-  of  water. 

1778.  All  methods  in  which  hydrocyanic  acid  is  obtained  by  dis-  Strength 
tillation  never  yield  this  energetic  preparation  of  the  same  quality 

and  strength;  even  with  the  application  of  every  possible  precaution, 
the  product  never  contains  more  than  four  fifths  of  the  small  quan- 
tity of  acid  which,  according  to  the  calculation,  ought  to  be  procured-; 
this  arises,  when  ferrocyanuret  of  potassium  is  used,  from  a portion 
of  the  cyanuret  entering  into  combination  with  the  protocyanuret  of 
iron  during  the  decomposition  of  the  yellow  salt,  or  from  the  impos- 
sibility of  effecting  an  absolute  condensation  of  so  volatile  a substance 
during  the  distillation. 

1779.  It  is  therefore  greatly  preferable  to  prepare  a stronger  acid  How  in- 
in  the  first  instance,  to  determine  by  experiment  the  quantity  of  an- 
hydrous acid  contained  in  it ; and  by  the  addition  of  water  to  bring 

it  to  that  degree  of  dilution  which  is  prescribed  by  the  physician,  or 
by  the  medical  laws  of  the  land.t  The  method  described  in  the  note 
may  be  used  for  testing  the  strength  of  any  solution  of  hydrocyanic 
acid  ; 100  grains  of  an  acid  which  contains  3 per  cent,  anhydrous 
prussic  acid  should,  when  precipitated  by  the  nitrate  of  silver,  give 
15  grains  of  the  cyanuret.  This  method  is  independent  of  all  acci-  Strength 
dents  which  can  possibly  have  an  influence  upon  the  activity  of  the  teste  * 
preparation  ; it  is  so  very  simple  that  it  will  yield  accurate  results  in 
every  hand.  The  peroxide  of  mercury,  which  is  readily  dissolved 
as  cyanide  at  common  temperatures,  may  also  be  used  to  test  the 
strength  of  the  aqueous  acid  ; a drop  or  two  of  caustic  potassa  is  ad- 


* Glasgow  Med.  Jour.  14. 

t For  example  2 parts  of  crystalline  ferrocyanuret  of  potassium  are  distilled  with  1 Method  of  test- 
part  of  sulphuric  acid  and  2 of  water  to  dryness  in  a chloride  of  calcium  bath  ; and  ius- 
the  product,  well  cooled  by  the  condensing  tube  apparatus,  collected  in  a narrow- 
mouthed bottle,  into  which  2 parts  of  water  have  been  placed.  The  quantity  obtained 
generally  amounts  to  4— 4£  parts  by  weight  of  liquid,  containing,  according  to  the 
more  or  less  perfect  cooling,  from  17 — 20  per  cent,  of  anhydrous  hydrocyanic  acid. 

The  exact  quantity  is  determined  in  the  following  manner:— One  drachm=60  grs.  of 
the  dilute  acid  is  added  to  a carefully  balanced  glass  vessel,  which  contains  a dilute 
solution  of  nitrate  of  silver,*  and  the  increase  of  weight  accurately  determined  ; by 
way  of  precaution,  a trial  is  made  to  see  whether  the  addition  of  the  silver  solution 
causes  a further  precipitation,  the  precipitate  collected  upon  a weighed  filter,  washed, 
dried,  and  the  quantity  of  cyanuret  of  silver  determined  by  a second  weighing.  Five 
parts  of  the  precipitate  correspond  to  1 part  of  the  hydrocyanic  acid.  If,  for  example 
52  grains  of  cyanuret  of  silver  be  obtained,  the  60  grains  of  dilute  acid  would  have 
consisted  of  10.4  grains  of  anhydrous  acid,  and  of  49.7  grains  of  water.  Were  it  de- 
sired, according  to  the  prescription  of  any  pharmacopoeia,  to  make  a hydrocyanic  acid 
containing  3 per  cent,  of  anhydrous  acid,  and  consequently  97  per  cent,  of  water,  it  is 
done  in  the  following  manner: — 3 hydrocyanic  acid  is  to  97  water  as  10.4  acid  is  to 
X = 336.2  water:  to  10.4  grains  of  anhydrous  acid  336.2  grains  of  water  must  be  ad- 
ded, in  order  to  form  a mixture  which  shall  contain  3 per  cent,  of  anhydrous  acid. 

To  each  drachm  of  the  product,  therefore,  since  it  consists  of  10.4  grains  of  anhydrous 
acid  and  49.6  of  water,  336.2 — 49.6  = 286.6  grains  of  water  must  be  added. 

* Nitrate  of  silver  is  an  exceedingly  delicate  test  of  the  presence  of  this  acid- 


408 


Cyanogen  and  Hydrogen. 


Chap.  VI. 


Properties. 


How  pre- 
served. 


Detection 
of  hydrocy- 
anic acid. 


Scheele's 

process. 


Las- 

saigne's 

process. 


ded  to  the  solution,  which  is  then  treated  with  a known  weight  of 
the  peroxide  in  fine  powder ; every  4 parts  of  the  oxide  dissolved 
corresponds  to  one  of  the  anhydrous  acid. 

1780.  The  properties  of  the  aqueous  acid  are  similar  to  those  of 
the  concentrated,  with  the  difference  of  taste,  odour,  and  poisonous 
and  combustible  properties,  which  are  dependent  on  a higher  or 
lower  degree  of  concentration  ; it  decomposes  when  perfectly  pure  as 
readily  as  the  anhydrous  acid,  becoming  brown,  and  at  last  black. 

1781.  Like  the  anhydrous  acid,  however,  it  may  be  preserved  by  ad- 
ding a trace  of  a strong  mineral  acid  ; a slight  permanent  reddening  of 
litmus  paper  should  not  therefore  be  considered  a sufficient  reason  for 
rejecting  an  acid  ; it  should  be  clear  and  colourless,  leave  no  residue 
on  evaporation,  nor  be  precipitated  or  blackened  by  hydrosulphuric 
acid  gas  (lead  or  mercury).  Treated  with  ammonia,  and  evaporated 
in  a water-bath,  the  dry  residue  should  not  exceed  one  quarter  per 
cent.  ; nor  should  it  become  brown  when  heated,  this  indicating  the 
presence  of  formic  acid,  which  may  also  be  detected  by  the  tests 
hereafter  to  be  mentioned.  Sulphuric  acid  is  detected  by  baryta  ; 
hydrochloric  acid  by  evaporating  in  a water-bath  till  all  odour  of 
prussic  acid  is  gone,  and  then  adding  a salt  of  silver.  By  careful 
rectification  over  chalk,  an  excess  of  mineral  acids  may  readily  be 
corrected  ; but  in  this  case  a trace  of  hydrochloric  or  sulphuric  acid 
must  be  added  afterwards,  to  give  stability  to  the  acid.  L.  769. 

1782.  As  this  acid  is  a very  powerful  poison,  all  experiments  with 
it  must  be  performed  with  the  greatest  caution.  Several  fatal  acci- 
dents have  occurred  ; even  the  fumes,  incautiously  inhaled,  produce 
severe  head-ache,  nausea,  and  fainting.  A single  drop  introduced 
into  the  throat  of  a large  dog,  kills  the  animal.  According  to  Herbst, 
the  best  antidote  is  the  cold  affusion. 

1783.  The  presence  of  the  free  acid  is  recognized  by  its  odour. 
Its  presence  in  the  stomach  after  death  may  be  detected  in  several 
ways.  The  sulphate  of  copper  forms  when  rendered  alkaline  by  a 
little  potassa,  a greenish  precipitate,  which  becomes  nearly  white, on 
the  addition  of  hydrochloric  acid,  but  this  is  of  less  value  than  the 
formation  of  Prussian  blue  as  proposed  by  Scheele : 

To  the  liquid  supposed  to  contain  hydrocyanic  acid,  add  a solution 
of  green  vitriol,*  throw  down  the  protoxide  of  iron  by  a slight  excess 
of  pure  potassa,  and  acidulate  with  hydrochloric  or  sulphuric  acid,  so 
as  to  redissolve  the  precipitate.  Prussian  blue  will  then  make  its 
appearance,  if  hydrocyanic  acid  had  been  originally  present.  The 
presence  of  protoxide  of  iron  is  essential. 

1784.  The  subject  has  been  investigated  experimentally  by  Leuret 
and  Lassaigne,  and  the  process  they  have  recommended  is  the  fol- 
lowing : 

The  stomach  or  other  substances  to  be  examined  are  cut  into  small  fragments, 
and  introduced  into  a retort  along  with  water,  the  liquid  being  slightly  acidulated 
with  sulphuric  acid.  The  distillation  is  then  conducted  by  the  heat  of  boiling 
water,  till  about  one  eighth  part  of  the  water  has  passed  over  into  the  receiver. 
To  the  distilled  liquid  add  a drop  of  caustic  potassa,  and  immediately  after  a very 
small  quantity  of  the  solution  of  sulphate  of  copper.  A small  quantity  of  matter 
will  be  disengaged  by  the  action  of  the  alkali  on  the  copper  solution.  Then  add 
one  or  two  drops  of  hydrochloric  acid.  If  no  hydrocyanic  acid  be  present,  the 


* Liebig  disapproves  of  this  test. 


409 


Cyanuret  of  Potassium. 

precipitate  will  be  dissolved  and  the  liquid  become  transparent ; but  if  any  of  the  Sect.  III. 
acid  is  present  it  will  remain  undissolved  and  white.  By  this  method  ^ otnr 
part  of  the  acid  may  be  detected.  There  is,  however,  a source  of  ambiguity  ; 
the  same  white  precipitate  will  remain  if  the  liquid  should  contain  hydriodic  acid. 

Sulphate  of  iron  when  substituted  for  sulphate  of  copper  will  detect  to-- .trou  °f 
the  weight  of  the  acid,  but  it  has  the  advantage  of  being  characteristic  in  conse- 
quence of  the  formation  of  Prussian  blue.* 

1785.  Hydrocyanate  of  Ammonia , Cyanuret  of  Ammonium.  Hydrocya- 
NH4Cy,  eq.  = 44.54.  Prepared  by  distilling  dry  ainmoniacal  salts  nateofam- 
with  metallic  cyanurets,  or  by  bringing  anhydrous  hydrocyanic  acid 

into  contact  with  ammoniacal  gas,  when  the  compound  is  produced 
in  the  form  of  bright  crystalline  plates.  It  is  almost  as  volatile  as 
the  acid  itself;  decomposes  very  rapidly  in  water,  is  poisonous,  and 
has  a strong  peculiar  smell. 

1786.  On  bringing  hydrocyanic  acid  into  contact  with  metallic  ox-  Hydrocya- 
ides  which  retain  their  oxygen  by  a feeble  affinity,  as  in  the  oxides  ofnieacid 
mercury,  silver,  palladium,  they  suffer  mutual  decomposition,  giving  j^oxides  ' 
rise  to  the  formation  of  water  and  a metallic  cyanuret ; if  no 

water  be  present,  the  decomposition  is  accompanied  by  so  great  an 
evolution  of  heat  as  to  cause  an  explosion.  The  alkaline  oxides 
unite  with  the  acid  without  decomposition ; in  this  class  of  com- 
pounds also  the  decomposition  of  the  acid  and  alkali  is  instantly 
effected,  when  the  solution  is  treated  with  another  metallic  cyanuret, 
with  which  they  form  a double  compound.  With  many  peroxides, 
as,  for  example,  with  the  peroxide  of  copper,  the  hydrocyanic  acid 
gives  rise  to  a corresponding  percyanuret ; but  this  is  decomposed 
either  instantly,  or  after  a short  time,  into  cyanogen  gas,  and  a pro- 
tocyanuret;  with  the  peroxide  of  lead  the  protocyanuret  is  formed, 
and  cyanogen  liberated. 

1787.  The  compounds  of  cyanogen  with  silver,  mercury,  and  Withsil- 
tnost  heavy  metals,  are  not  decomposed  by  dilute  ox-acids,  and  are  ver’  ^c' 
with  difficulty  decomposed  by  concentrated  nitric  acid  at  a boiling 
temperature;  many  of  them  with  great  facility  by  hydrosulphuric 

and  hydrochloric  acid  into  hydrocyanic  acid,  and  a metallic  sul- 
phuret  or  chloride  (cyanurets  of  mercury,  silver).  The  cyanurets 
of  the  precious  metals  (silver,  mercury)  are  decomposed  by  heat  like 
the  corresponding,  oxides  into  cyanogen  and  metal ; the  cyanurets  of 
the  heavy  metals  into  a carburet  and  free  nitrogen  ; the  cyanurets 
of  the  alkaline  metals,  if  protected  from  the  action  of  the  air  and 
moisture,  will  bear  a very  high  temperature  without  decomposition. 

1788.  All  insoluble  cyanurets  of  the  heavy  metals  may  be  formed  insoluble 
by  adding  hydrocyanic  acid  to  the  acetate.  They  are  decomposed  cyanurets 
on  being  heated  in  a large  excess  of  hydrochloric  acid  or  in  hydrate 

of  potassa  into  a metallic  chloride,  or  into  an  oxide,  ammonia,  and 
formic  acid  ; the  latter  is  the  case  with  the  alkaline  cyanurets  when 
boiled  in  an  excess  of  alkali.  All  metallic  cyanurets,  the  correspond- 
ing oxides  of  which  do  not  retain  carbonic  acid  at  a red  heat,  evolve, 
when  burnt  with  oxide  of  copper,  nitrogen  and  carbonic  acid  gases 
in  the  proportion  1 : 2 by  volume. 

1789.  Cyanuret  of  Potassium.  KCy  eq.  65.54.  Formed,  when  Cyanuret 
potassium  is  heated  in  cyanogen  gas  with  the  appearance  of  com-  of  Potassi- 


52 


* Ann.  de  Chim.  et  Phys.  xxvii.  200. 


410 


Chap.  VI. 


Prepared. 


Properties. 


Action  of 
water. 


Cyanuret 
oi  iron. 


Cyanogen  and  its  Compounds . 

bustion,  by  heating  potassium  with  anhydrous  substances  containing 
nitrogen,  by  heating  the  carbonate  of  potassa  to  redness  with  matter 
containing  carbon  and  nitrogen. 

By  adding  hydrocyanic  acid  in  excess  to  a recently  prepared  concentrated  so- 
lution of  caustic  potassa,  evaporating  the  solution  in  a retort  at  a boiling  heat  till 
crystallization  commences,  when  it  must  be  poured  into  a porcelain  dish  and 
fused  at  a low  red  heat.  Or  a saturated  alcoholic  solution  of  hydrate  of 

fiotassa  is  treated  with  strong  hydrocyanic  acid  in  successive  portions  as 
ong  as  it  throws  down  a white  crystalline  precipitate,  which  should  be 
washed  with  alcohol  and  dried.  An  additional  quantity  is  obtained  by  eva- 
porating the  liquid  in  a retort.  Or  better  by  heating  the  ferrocyanuret  of  po- 
tassium, carefully  dried  and  reduced  to  a fine  powder,  in  an  iron  vessel  or  well- 
closed  crucible  to  a strong  red  heat,  exposure  to  the  air  being  carefully  avoided  till 
auite  cold ; the  semi-fused  or  black  porous  mass  must  then  be  reduced  to  a 
nne  powder,  placed  in  a funnel,  moistened  with  a little  alcohol,  and  then 
washed  with  cold  water.  The  first  concentrated  colourless  solution  which 
passes  off,  is  rapidly  brought  to  dryness  and  fused  in  a porcelain  dish.  The 
pounded  fused  mass  may  also  be  boiled  in  spirit  when  the  cyanuret  is  depo- 
sited in  crystals  on  cooling.  Alcohol  of  60  per  cent,  dissolves  at  the  boiling 
temperature  a considerable  quantity  of  the  cyanuret,  almost  the  whole  of 
which  is  again  deposited  as  the  solution  cools;  if  it  be  stronger  or  weaker, 
this  does  not  occur.  The  application  of  warm  water  in  the  preparation  must 
be  altogether  avoided,  as  when  air  is  present  it  at  once  colours  the  so- 
lution yellow,  owing  to  the  reproduction  of  the  ferrocyanuret  of  potassium. 

1790.  Colourless,  crystallizes  in  transparent  cubes,  or  other  forms 
of  the  oetohetlral  system,  without  odour,  but  of  a sharp  biting  alka- 
line and  bitter-almond  taste ; fuses  readily  to  a clear  transparent 
liquid,  and  will  bear  a white  heat  without  decomposition  in  close 
vessels  ; exposed  to  oxygen,  on  the  contrary,  it  is  converted  into  cy- 
anate  of  potassa.  On  exposure  the  crystals  become  opaque,  deli- 
quesce in  a moist  atmosphere,  are  very  soluble  in  water,  the  solution 
is  decomposed  even  by  the  carbonic  acid  of  the  air,  and  smells  of 
prussic  acid.  Even  kept  in  close  vessels  it  decomposes  in  a shorter 
or  longer  time. 

1791.  The  cyanuret  of  potassium  is  converted,  when  dissolved  in 
water,  into  hydrocyanate  of  potassa  ; if  the  solution  be  evaporated  with 
an  excess  of  potassa,  the  whole  of  the  nitrogen  is  evolved  as  ammo- 
nia, and  formate  of  potassa  remains.  Effervescence  on  the  addition 
of  an  acid  proves  the  presence  of  carbonic  acid  ; a yellow  colour, 
that  of  iron  ; and  a blackening  when  heated,  the  admixture  of  salts 
of  formic  acid.  It  may  be  used  instead  of  the  hydrocyanic  acid. 

1792.  Cyanuret  of  Iron.  FeCy  ; eq.=54.39.  This  compound, 
remarkable  from  its  tendency  to  form  a very  peculiar  class  of  double 
compounds  by  uniting  with  other  cyanurets,  would  appear  as  inca- 
pable of  existing  in  a free  state  as  the  corresponding  protoxide.  On 
adding  a proto-salt  of  iron  to  a solution  of  cyanuret  of  potassium,  a 
yellowish-red  precipitate  is  formed,  which  is  redissolved  by  an  ex- 
cess of  the  cyanuret  into  a yellow  liquid,  the  ferrocyanuret  of  potas- 
sium. On  heating  dry  ferrocyanuret  of  ammonium,  cyanuret  of 
ammonium  is  evolved,  and  a gray  insoluble  powder,  which  has  been 
considered  as  this  compound,  is  the  residue  obtained.  It  is  also 
produced,  according  to  Robiquet,  by  pouring  a saturated  solution  of 
hydrosulphuric  acid  over  recently  precipitated  Prussian  blue  con- 
tained in  a well-stoppered  vessel ; the  Prussian  blue  becomes  white, 


411 


Cyanuret  of  Palladium . 

and  the  solution  contains  hydrocyanic  acid.^  The  properties  of  Sect,  m. 
these  preparations  differ  too  widely  to  allow  of  their  being  considered 
as  identical.! 

1793.  Bicyanuret  of  Mercury.  HgCy2,  eq.  =254.78.  An  aque-  Bicyanuret 
ous  solution  of  prussic  acid  is  treated  with  finely  powdered  peroxide  0 mercury* 
of  mercury  until  all  odour  of  the  former  disappears ; the  liquid 

yields  on  evaporation  perfectly  pure  crystals  of  the  bicyanuret. 

For  this  purpose  the  acid  prepared  as  recommended  by  Geiger  is  most  conve-  Process, 
nient ; it  should  be  introduced  into  a well-stopped  bottle,  and  the  combination 
with  the  oxide  of  mercury  promoted  by  frequent  agitation.  It  must  always  be 
remembered,  that  the  compound  can  only  be  produced  when  water  is  present  in 
sufficient  quantity  to  dissolve  the  whole  of  the  cyanuret;  water  must  therefore 
be  added,  should  it  be  observed  that  the  liquid  smells  of  prussic  acid,  while  any 
portion  of  the  oxide  of  mercury  remains  undissolved.  Or  by  adding  to  a solution 
of  2 parts  of  ferrocyanuret  of  potassium  in  15  parts  of  boiling  water,  3 parts  of 
perfectly  dry  bisulphate  of  the  peroxide  of  mercury  ; boil  the  mixture  for  a quar- 
ter of  an  hour,  and  separate  the  clear  liquid  while  boiling  hot  from  the  precipitate 
by  filtration  ; as  the  solution  cools,  the  bicyanuret  crystallizes.  The  mother- 
liquor  yields  a second  crop  of  crystals  by  further  concentration ; or  it  may  be 
evaporated  to  dryness,  and  the  cyanuret  obtained  from  the  residue  by  boiling  al- 
cohol. The  first  crystals  from  the  aqueous  solution  are  purified  by  a second 
crystallization. 

1794.  The  formation  of  the  cyanide  in  this  process  is  owing  to  Explained, 
the  mutual  decomposition  between  the  2 eq.  of  cyanuret  of  potassium 

of  the  ferrocyanuret  and  2 eq.  of  persulphate  of  mercury  into  bicya- 
nuret of  mercury  and  sulphate  of  potassa,  while  the  cyanuret  of  iron 
is  precipitated. 

1795.  Crystallizes  in  colourless  transparent  regular  four  or  six-  Properties, 
sided  prisms ; they  are  anhydrous,  permanent  in  the  air,  of  a very 
disagreeable  metallic  taste,  and  are  very  poisonous.  Is  dissolved  by 

8 parts  of  water  at  60°,  but  is  more  soluble  in  boiling  water,  and  in 
alcohol. 

Peroxide  of  mercury  decomposes  all  soluble  metallic  cyanurets 
with  the  formation  of  an  oxide  and  double  cyanurets  of  mercury  and 
other  metals.! 

1796.  Cyanuret  of  Silver.  AgCy,  eq.  134.39.  Falls,  on  mixing  Cyanuret 
a soluble  salt  of  silver  with  hydrocyanic  acid,  in  the  form  of  a bril-  si*ver‘ 
liant  white  curdy  precipitate ; is  decomposed  by  all  hydracids,  but 

with  great  difficulty  by  other  mineral  acids  ; strong  boiling  nitric 
acid  alone  can  dissolve  it ; suffers  no  change  by  the  caustic  fixed  al- 
kalies, is  readily  dissolved  by  ammonia.  Is  soluble  in  a concen- 
trated solution  of  the  nitrate  of  silver,  forming  with  it  a compound, 
which  may  be  obtained  in  crystals,  but  is  not  permanent  in  water. 

It  gives  rise  to  double  compounds  with  all  cyanurets  of  the  alkaline 
metals. 

1797.  Cyanuret  of  Palladium.  PdCy,  eq.  79.69.  The  affinity  Cyanuret 
of  palladium  for  cyanogen  surpasses  that  of  all  other  metals  ; they 

* Berzelius. 

t Sesqui,  and  Proto  cyanurets  of  Iron,  FeCy-fFe2Cy3-)-4  aq. 

$ If  the  bicyanuret  be  boiled  with  an  excess  of  peroxide  of  mercury,  the  latter  is  dis- 
solved in  large  quantity  (3  eq.  Kuhn),  and  the  solution  on  evaporation  deposits  a 
compound  in  fine  acicular  crystals;  these  are  more  soluble  in  cold  water  than  the  bi- 
cyanuret, and  have  an  alkaline  reaction  on  vegetable  colours.  The  formation  of  this 
compound,  during  the  preparation  of  the  bicyanuret,  must  be  carefully  avoided,  or 
only  a white  saline  mass  may  be  obtained.  This  is  best  done  by  the  careful  addition 
of  hydrocyanic  acid  until  its  odour  is  slightly  perceptible. 


412 


Chap.  VI. 


Percyanu- 
ret  of  gold. 


Double  cy- 
an urets  of 
the  metals. 


Constitu- 
tion of  the 
double 
compounds 
of  iron  and 
cyanogen. 


Hydro-fer- 

rocyanic 

acid. 

Process. 


Cyanogen  and  its  Compounds. 

combine,  whenever  hydrocyanic  acid  or  any  soluble  cyanuret  is  ad- 
ded to  a salt  of  the  oxide  of  palladium,  in  the  form  of  a light  chest- 
nut precipitate,  which  has  a greenish  tint  if  copper  be  present ; 
gives  rise  to  double  salts  with  ammonia,  cyanuret  of  potassium,  and 
nitrate  of  the  oxide  of  palladium. 

1798.  Per  cyanuret  of  Gold.  AuCy3,eq. =278.17.  This  compound 
has  recently  been  used  medicinally. 

A solution  of  gold  in  aqua  iegia,  carefully  deprived  of  all  free  acid  by  evapo- 
ration, is  precipitated  by  a recently  prepared  solution  of  caustic  potassa  to  which 
hydrocyanic  acid  has  been  added  in  excess ; care  must  be  taken  that  a small  quan- 
tity of  the  chloride  of  gold  remain  in  the  solution.  The  yellowish-white  preci- 
pitate is  collected,  washed,  and  dried.  An  excess  of  cyanuret  of  potassium 
dissolves  the  precipitate,  and  the  solution  has  a yellowish-red  colour,  but  in  this 
case  it  is  re-precipitated  by  the  addition  of  an  acid.  It  may  also  be  prepared  by 
adding  to  16  parts  of  gold  dissolved  in  aqua  regia  by  the  aid  of  heat  a boiling  so- 
lution of  24  parts  of  bicyanuret  of  mercury,  evaporating  to  dryness,  and  washing 
with  pure  water. 

1799.  All  insoluble  metallic  cyanurets  (the  heavy  metals)  combine 
with  the  soluble  (the  alkaline  metals)  to  peculiar  generally  crystal- 
lizable  double  compounds,  which  are  very  similar  in  their  general 
properties  to  the  combinations  of  the  soluble  and  insoluble  metallic 
sulphurets.  On  mixing  a double  cyanuret  of  potassium  or  sodium 
with  a metallic  salt,  the  basis  of  which  is  an  oxide  of  a heavy  metal, 
a new  double  compound  is  generally  formed,  arising  from  the  re- 
placement of  the  alkali  by  its  equivalent  of  the  heavy  metal.  The 
double  cyanuret  of  silver  and  potassium,  KCy-|-AgCy,  forms,  with 
acetate  of  lead,  PbOA,  the  double  cyanuret  of  silver  and  lead,  PbCy 
-)-AgCy,  and  acetate  of  potassa. 

1800.  The  composition  of  these  compounds  is  best  explained  by 
supposing  the  existence  of  a radical,  which  contains  1 eq.  of  iron  in 
combination  with  carbon  and  nitrogen  in  the  same  proportion  as  they 
exist  in  cyanogen,  but  in  such  quantity  as  would  form  3 eq.  of  the 
latter,  and  which,  by  uniting  with  2 eq.  of  hydrogen,  form  a bibasic 
acid.  The  radical  itself  may  be  called  ferrocyariogen  ; the  acid, 
hydro-ferrocyanic  acid  ; and  the  compounds  of  the  radical  with  the 
metals  by  the  same  adjuncts  to  ferrocvanuret  as  are  used  lor  the 
corresponding  oxides. 

The  ferrocyanogen  is  composed  of 

3 eq.'  nUrogen  \ =3  eq  cyauoSen+l  eq.  iron=l  eq  ferrocyanogen  j symb.  Cfy. 

Compounds  of  Ferrocyanogen. 

1801.  Hydro- Ferrocyanic  Acid.  Cfy-j-2H,  eq.=109.17.  Disco- 
vered by  Porrett. 

Prepared  by  decomposing  recently  precipitated  ferrocyanuret  of  lead  or  copper 
by  sulphuretted  hydrogen  ; filter  to  separate  the  metallic  sulphuret,  and  evapo- 
rate over  sulphuric  acid  in  vacuo.*  Or  by  mixing  pure  Prussian  blue  with  ten 
times  its  volume  of  concentrated  hydrochloric  acid,  and  as  soon  as  the  blue 
colour  has  disappeared,  and  the  insoluble  portions  have  become  yellow  or  brown, 
washing  it  well  with  fresh  portions  of  the  concentrated  acid  ; the  moi9t  mass 
should  be  spread  out  upon  a clean  tile,  placed  under  a bell-jar  with  quick 
lime,  and  when  dry  dissolved  in  alcohol,  and  the  solution  spontaneously  eva- 
porated.t 


* Berzelius. 


t Robiquet. 


413 


Ferrocyanuret  of  Potassium . 

1802.  A white  distinctly  crystalline  mass,  or  small  granular,  some-  Sect,  m. 
times  acicular  crystals,  which  acquire  a blue  colour  by  exposure  to  Properties, 
the  air.  The  aqueous  solution  is  decomposed  by  boiling  into  hydro- 
cyanic acid,  and  a white,  but  after  exposure  in  open  vessels  blue, 
precipitate.  The  hypothetical  radical  of  the  acid  can  (probably)  not 

be  isolated. 

1803.  Ferrocyanuret  of  Ammonium.  It  may  be  formed  by  digest-  Ferrocyan- 
ing  at  a gentle  heat  the  ferrocyanuret  of  lead  with  carbonate  of  am-  uret  of  am- 
monia; filtering  to  separate  tbe  carbonate  of  lead,  and  evaporating rnomum' 
to  crystallization.  It  is  isomorphous  with  the  ferrocyanuret  of  po- 
tassium ; the  crystals  are  white,  or  yellowish-white,  transparent, 
permanent  in  the  air,  very  soluble  in  cold,  but  decomposed  by  boiling 

water  into  cyanuret  of  ammonium  and  cyanuret  of  iron,  insoluble  in 
alcohol.  It  forms  with  sal  ammoniac  a double  salt,  which  is  obtain- 
ed by  boiling  a solution  of  equal  parts  of  ferrocyanuret  of  potassium 
and  sal  ammoniac  in  6 parts  of  water,  when  it  forms,  on  cooling, 
large  lemon-yellow  crystals,  which  are  very  brittle  and  permanent 
in  the  air.  They  are  composed  of  an  eq.  of  ferrocyanuret  of  ammo- 
nium, 1 of  sal  ammoniac,  and  3 eq.  water.^ 

1804.  On  bringing  the  hydro-ferrocyanic  acid  into  contact  with  Hydro-fer- 
metallic  oxides,  the  latter  are  reduced  by  the  hydrogen  of  the  acidj.^y^J 
water,  and  a compound  of  the  metal  with  the  radical  of  the  acid  be-  metallic ox- 
ing  formed  ; as  1 eq.  of  the  acid  contains  2 eq.  of  hydrogen,  it  fol-  ides, 
lows  as  a necessary  consequence  that  it  decomposes  2 eq.  of  the 

most  numerous  class  of  oxides,  in  which  1 eq.  of  oxygen  is  present 
in  1 eq.  of  the  oxide. 

1805.  The  ferrocyanurets  are,  without  exception,  decomposed  Decompos- 
when  exposed  to  a red  heat  in  close  vessels  ; those  which  contain  an  ed  by  heat' 
alkaline  metal  give  rise  to  the  formation  of  the  cyanuret  of  that 

metal,  a carburet  of  iron,  and  the  evolution  of  nitrogen  gas  ; all 
others  yield  mixtures  of  metals  and  metallic  carburets,  with  or  without 
the  evolution  of  cyanogen.  All  the  soluble  ferrocyanurets  are  decom- 
posed by  being  boiled  with  peroxide  of  mercury  into  perycyanuret  of 
mercury,  free  alkali,  and  oxy-cyanuret  of  iron.  The  ferrocyanurets  of 
potassium  and  sodium  are  converted  by  being  calcined  in  open  ves- 
sels into  alkaline  cyanates,  and  the  black  oxide  or  carburet  of  iron. 

1806.  Most  of  the  ferrocyanurets  contain  water  of  crystallization,  Properties, 
which  they  lose  when  heated.  Those  of  zinc,  copper,  and  mercury 

unite  with  ammonia  to  peculiar  crystalline  double  compounds.!  Most 
of  them  are  soluble  in  concentrated  sulphuric  acid  without  decompo- 
sition ; or  they  unite  with  it,  when  they  lose  their  colour,  to  saline 
combinations  in  which  the  ferrocyanuret  acts  the  part  of  a base.  By 
nitric  acid  they  are  decomposed,  many  of  them  with  the  evolution  of 
cyanogen  and  the  formation  of  metallic  ferrid-cyanurets.  When 
those  which  are  soluble  in  water  are  boiled  with  dilute  acids,  the 
hydro-ferrocyanic  acid  is  separated,  and  at  that  temperature  decom- 
posed into  hydrocyanic  acid  which  escapes,  and  into  the  white  but 
impure  protocyanuret  of  iron,  which,  on  exposure  to  the  air,  absorbs 
oxygen  and  becomes  blue. 

1807.  Ferrocyanuret  of  Potassium.  In  crystals  K2Cfy-|-3  aq.,  eq.  Ferrocya- 
=185.47.  This  compound  occurs  of  great  purity  in  commerce,  and  is  potassium. 


* Bunsen. 


+ Ibid. 


414 


Chap  VI. 
Process. 


Explained. 


Effect  of 
air. 


Air  exclud- 
ed. 


Properties. 


Protoiulphatf 
of  iron  useful. 


Cyanogen  and  its  Compounds. 

prepared  on  a large  scale  by  fusing  substances  which  are  rich  in  ni- 
trogen, as  horn,  hoof,  and  dried  blood,  with  2 — 3 parts  of  carbonate 
of  potassa  in  iron  vessels  ; the  mass  after  perfect  fusion  is  allowed  to 
cool,  the  soluble  parts  removed  by  boiling  water  from  which  the  fer- 
rocyanuret  is  obtained  by  crystallization.  It  may  be  obtained  on  a 
small  scale  by  boiling  Prussian  blue  in  carbonate  of  potassa. 

1808.  By  the  fusion  of  substances  containing  carbon  and  nitrogen 
with  carbonate  of  potassa  at  a red  heat,  the  potassa  is  reduced  by  a 
portion  of  the  carbon  to  potassium,  by  the  reaction  of  which  on  the 
rest  of  the  materials  cyanuret  of  potassium  as  the  principal  product 
is  formed.  The  red-hot  fused  mass  does  not  contain  a particle  of 
the  ferrocyanuret,  but  it  contains,  in  the  form  of  a black  slime,  a 
large  quantity  of  finely  divided  metallic  and  carburetted  iron.  If  the 
mass  be  treated  with  cold  water,  and  the  solution  evaporated,  no 
ferrocyanuret  is  obtained ; but  if,  while  covered  with  water,  it  is 
freely  exposed  to  the  air  and  gently  warmed  for  some  hours,  oxygen 
is  rapidly  absorbed,  and  a yellow  solution  is  obtained,  which  is  rich 
in  ferrocyanuret  of  potassium;  this  arises  from  the  solution  of  pure 
cyanuret  of  potassium  dissolving  iron  when  oxygen  is  present  with 
the  formation  of  potassa;  the  potassium,  therefore,  of  the  cyanuret, 
by  uniting  with  oxygen,  gives  the  cyanogen  to  the  iron,  by  which 
the  latter  is  converted  into  cyanuret,  and  thus  acquires  the  property 
of  uniting  with  undecomposed  cyanuret  of  potassium  to  the  ferrocy- 
anuret. 

1809.  In  close  vessels  the  solution  of  iron  by  cyanuret  of  potassi- 
um is  attended  with  the  evolution  of  hydrogen,  owing  to  the  decom- 
position of  water,  the  oxygen  of  which  unites  with  the  potassium, 
while  the  cyanogen  passes  over  to  the  iron.  The  fused  mass  con- 
tains a large  quantity  of  free  potassa,  which,  by  being  boiled  with  the 
cyanuret  of  potassium,  causes  the  decomposition  of  the  latter  into 
formate  of  potassa  and  ammonia  ; if  the  animal  substances  be  fused 
in  open  vessels  with  the  potassa,  a portion  of  the  cyanuret  of  potas- 
sium is  burnt  into  cyanate  of  potassa,  the  solution  of  which  is  decom- 
posed by  boiling  into  ammonia  and  bicarbonate  of  potassa.  The 
ammonia  arises  in  every  case  from  the  decomposition  of  the  cyanuret 
of  potassium  ; its  formation  is  consequently  always  accompanied  by 
a corresponding  loss,  and  should  be  most  carefully  avoided.* 

1810.  Crystallizes  in  large  quadrangular  tables  or  short  prisms 
with  truncated  edges  and  angles,  which  belong  to  the  square  pris- 
matic system  ; is  of  a lemon-yellow  colour,  of  sp.  gr.  1.832  ; has  at 
first  a sweetish  bitter,  but  afterwards  saline  taste  ; is  permanent  in 
the  air,  loses  at  212°  12.82  per  cent.=3  eq.  of  water,  and  becomes 
white  ; is  soluble  in  4 parts  of  cold  and  in  2 parts  of  boiling  water ; 
is  insoluble  in  alcohol,  by  which  it  is  precipitated  from  its  aqueous 


* It  is  best  to  treat  one  third  either  by  volume  or  weight  of  a cold  solution  of  the  raw 
mass  with  pr  >tosulphate  of  iron  as  long  as  a precipitate  falls,  then  add  the  remaining 
two  thirds  of  the  solution,  and  bring  the  whole  to  the  boiling  point}  it  must  always  be 
remembered  that  the  solution  must  contain  free  potassa.  In  this  manner  sulphate  of 
potassa  is  obtained,  and  all  the  cyanuret  of  potassium  is  converted  without  any  loss 
into  the  ferrocyanuret ; the  solution  can  be  evaporated  without  decomposition,  and  the 
sulphate  of  potassa  is  easily  separated  by  crystallization.  The  raw  solution  generally 
contains  some  sulphocyanuret  of  potassium,  sulphuret  of  potassium,  formate  and  car- 
bonate of  potassa,  all  of  which  remain  in  the  mother  liquor. 


415 


Sesqui-ferrocyanuret  of  Iron . 

solution  in  brilliant  yellow  flakes.  Is  converted  by  nitric  acid,  with  Sect,  in. 
the  escape  of  cyanogen,  and  by  chlorine,  into  the  ferrid-cyanuret  of 
potassium.  At  a red  heat  it  is  decomposed  into  the  carburet  of  iron 
and  cyanuret  of  potassium,  but  by  the  action  of  atmospheric  air  the 
latter  is  converted  into  cyanate  of  potassa. 

1811.  The  ferrocyanuret  of  potassium  forms  double  compounds  Use. 
with  other  ferrocyanurets.  It  is  used  as  a test  for  the  oxide  of  iron 

in  solution.  When  thus  employed,  however,  it  must  be  remem- 
bered that  the  solution  must  not  have  an  alkaline  reaction,  for  all 
solutions  of  oxide  of  iron  which  contain  free  ammonia  are  not  preci- 
pitated by  the  ferrocyanuret  of  iron. 

It  is  used  for  the  preparation  of  hydrocyanic  acid,  percyanuret  of 
mercury,  Prussian  blue,  &c. ; taken  in  largo  doses  is  purgative  and 
not  poisonous.* 

1812.  Ferrocyanuret  of  Mercury.  On  mixing  a solution  either  Ferrocya- 
ofpro-  or  peroxide  of  mercury  with  ferrocyanuret  of  potassium  a white  nuret  of 
precipitate  falls,  which  spontaneously  decomposes  into  cyanuret  0fmercuiT* 
mercury  which  is  re-dissolved,  and  into  cyanuret  of  iron.  This 
change  is  rendered  more  rapid  by  the  aid  of  heat,  and  metallic  mer- 
cury is  separated  when  a proto-salt  of  mercury  has  been  used. 

1813.  Ferrocyanuret  of  potassium  produces  white  precipitates  with  Colour  of 
the  salts  of  silver,  zinc,  and  bismuth,  a greenish-white  with  those 

of  nickel,  and  green  with  cobalt ; but  the  latter,  by  taking  up  water, 
become  reddish-gray  ; with  salts  of  protoxide  of  manganese  a white 
precipitate  is  first  formed,  but  it  afterwards  acquires  the  colour  of 
peach-blossoms. 

1814.  Sesquiferrocyanuret  of  Iron.  Discovered  by  Diesbach  in  prussian 
Berlin  in  1710,  from  which  it  became  generally  known  as  Prussian  blue. 

or  Berlin  blue-  It  is  formed  whenever  a salt  of  peroxide  of  iron  is 
added  to  a soluble  metallic  ferrocyanuret ; compounds  similar  in  co- 
lour, but  different  in  constitution,  although  likewise  known  by  the 
name  of  Prussian  blue,  may  be  obtained  by  precipitating  the  ferrid- 
cyanuret  of  potassium  by  a salt  of  the  protoxide  of  iron,  or  by  preci- 
pitating the  ferrocyanuret  of  potassium  by  a proto-salt  of  iron,  adding 
an  acid,  and  exposing  the  precipitate  to  the  air  until  it  becomes  blue. 

By  precipitating  a solution  of  perchloride  or  pernitrate  of  iron  by  ferrocyanuret  Process, 
of  potassium,  care  being  taken  to  avoid  an  excess  of  the  latter.  Or  by  dissolving 
6 parts  of  green  vitriol  and  (5  parts  of  ferrocyanuret  of  potassium  each  by 
itself  in  15  parts  of  water,  mixing  the  two  solutions,  and  then  adding  to  them  1 
part  of  concentrated  sulphuric  acid  and  24  parts  of  fuming  hydrochloric  acid  un- 
der constant  stirring.  After  some  hours  the  whole  should  be  treated  with  a 
clear  solution  of  1 part  of  bleaching-powder  in  80  of  water,  added  in  successive 
portions,  care  being  taken  to  stop  the  addition  of  the  bleaching  liquid  as  soon  as 
an  effervescence  arising  from  the  escape  of  chlorine  gas  is  observed.  After  stand- 
ing some  hours,  the  precipitate,  should  be  thoroughly  washed!  and  dried,  either 
at  common  or  high  temperatures.  Or  the  precipitate  may  be  treated  with  dilute 
nitric  acid  till  it  is  rendered  of  a deep  blue  colour.  This  yields  the  finest  pro- 
duct.! 

1815.  Prussian  blue  dried  at  common  temperatures  is  a ligh.t  po-  Properties, 
rous  body  of  a deep  velvet-blue  colour;  dried,  on  the  contrary,  at 

high  temperatures,  it  has  a deep  copper-red  colour,  but  the  powder 

* For  other  ferrocyanurets  see  Liebig  and  Turner’s  Elements , 780. 

t Hochstatter. 

t For  details  of  the  manufacture,  see  lire’s  Did.  Arts  and  Manuj.  1040, 


416 


Chap.  VI. 


Chemical 

constitu- 

tion. 


Effect  of 
light. 


Ferrocya- 
nurets  with 
two  basic 
metals. 


Ferrocya- 
nuret  of  po- 
tassium 
and  iron. 


Cyanogen  and  its  Compounds. 

is  blue  ; it  is  tasteless,  insoluble  in  water  and  dilute  acids,  and  is  not 
poisonous.  The  painter’s  Prussian  blue  of  commerce  contains  vari- 
able quantities  of  earthy  matter.  When  heated  in  close  vessels, 
water,  hydrocyanic  acid,  and  carbonate  of  ammonia  are  evolved,  and 
carburet  of  iron  is  the  residue  ; it  may  be  kindled  in  the  air  by  a 
red-hot  body,  when  it  burns  slowly  to  oxide  of  iron;  it  is  decomposed 
by  fuming  nitric  acid,  but  strong  sulphuric  acid  unites  with  it,  form- 
ing a white  mass  of  the  consistence  of  paste.  Concentrated  hydro- 
cyanic acid  deprives  it  of  its  iron,  and  liberates  the  hydro-ferrocyanic 
acid;  sulphuretted  hydrogen  whitens  it,  but  the  colour  returns  on 
exposure  to  the  air ; metallic  zinc  and  iron  have  a similar  action. 
By  peroxide  of  mercury  it  is  decomposed  into  percyanuret  of  mer- 
cury, and  an  insoluble  mixture  of  oxide  and  cyanuret  of  iron  ; by 
alkalies,  into  soluble  ferrocyanurets  and  peroxide  of  iron. 

1816.  In  reference  to  the  constitution  of  this  compound,  it  is 
known  with  certainty  that  it  differs  from  all  other  ferrocyanurets. 
It  contains  hydrogen  and  oxygen,  which  cannot  be  separated  without 
the  decomposition  of  the  compound,  so  that  it  must  be  considered  as 
formed  by  the  union  of  hydro-ferrocyanic  acid  with  the  peroxide  of 
iron  combined  without  reduction.  According  to  the  experiments  of 
Berzelius,  the  weight  of  the  iron  of  the  hydro-ferrocyanic  acid  is  to  that 
of  the  oxide  as  3 : 4 ; from  this  it  may  be  concluded  that  its  forma- 
tion is  owing  to  the  decomposition  of  3 eq.  of  ferrocyanuret  of  po- 
tassium, and  2 eq.  of  peroxide  of  iron,  into  6 eq.  of  a potassa  salt  and 
into  Prussian  blue. 

S+60  | =(3Cfy+2Fea)+6KO. 

IS17.  Prussian  blue  becomes  white  in  the  direct  rays  of  the  sun, 
and  cyanogen  is  evolved ; but  in  the  dark  it  absorbs  oxygen  and  re- 
covers its  colour.*  This  change  of  colour  in  substances  dyed  with 
Prussian  blue  in  solar  light,  arises  from  a peculiar  decomposition  ; 
the  recovery  of  the  colour  is  owing  to  the  formation  of  the  so-called 
basic  Prussian  blue. 

1818.  When  concentrated  solutions  of  the  salts  of  baryta,  strontia, 
lime,  magnesia,  protoxide  of  iron,  protoxide  of  manganese,  copper, 
&c.,  are  added  to  a solution  of  the  ferrocyanurets  of  potassium,  white 
bulky,  frequently  crystalline,  precipitates  are  formed,  which  arise 
from  the  replacement  of  1 eq.  of  potassium  by  1 eq.  of  the  other 
metal.  These  double  ferrocyanurets  which  contain  an  alkaline  me- 
tal, although  with  difficulty,  are  nevertheless  soluble  in  water;  they 
contain  water  of  crystallization  ; when  dried  at  a high  temperature 
they  glow  with  a brilliant  light,  and  cyanate  of  potassa  is  formed. t 

1819.  Ferrocyanuret  of  Potassium  and  Iron  is  obtained  in  the 
form  of  a bluish-white  precipitate  when  a salt  of  the  protoxide  of  iron 
is  added  to  a solution  of  the  ferrocyanuret  of  potassium.  By  the 
action  of  chlorine  or  nitric  acid  3 eq.  of  potassium  and  1 eq.  of  iron 
are  removed  from  3 eq.  of  the  compound  ; Prussian  blue  is  left.  Ex- 
posed to  the  air  it  absorbs  oxygen  and  becomes  blue  ; when  washed, 
the  ferrocyanuret  of  potassium  is  dissolved,  and  after  all  soluble 
salts  are  removed  the  following  compound  is  left. 


* Chevreul. 


t Campbell. 


417 


Hydro-ferridcyanic  Acid. 

1820.  Basic  Sesqui-ferrocyanuret  of  Iron.  By  continued  washing  Sect,  hi. 
the  preceding  salt  dissolves,  without  leaving  any  residue  of  oxide  of  Basic  ses- 
iron,  to  a beautiful  deep  blue  solution,  which  may  be  again  evapo- 

rated  to  dryness  without  decomposition.  The  addition  of  any  salt  jron. 
causes  the  separation  of  the  compound  ; the  precipitate  may  be  re- 
dissolved in  pure  water,  and  is  not  throvvn  down  by  alcohol.*  The 
formation  of  this  soluble  salt  is  prevented  by  the  presence  of  a strong 
acid,  which  unites  with  the  peroxide  of  iron,  and  Prussian  blue  is 
left. 

1821.  Ferrocyanuret  of  Potassium — Sesqui-ferrocyanuret  of  Iron.  Ferrocya- 
The  blue  precipitate  which  falls  when  a salt  of  the  peroxide  of  iron  taSrseium.P°" 
is  added  to  a solution  of  ferrocyanuret  of  potassium,  always  contains, 

when  the  iron  salt  is  in  excess,  variable  quantities  of  the  ferrocyanu- 
ret of  potassium;  the  latter  may,  by  continued  washing  with  water, 
gradually,  although  with  great  difficulty,  be  removed,  which  ac- 
counts for  the  constant  presence  of  potassium  in  the  Prussian  blue  of 
commerce ; it  varies  from  2 to  9 per  cent.! 

1822.  Ferrocyanuret  of  Potassium — Ferrocyanuret  of  Zinc , is  ob-  Ferrocya- 
tained  by  precipitating  any  salt  of  zinc,  which  is  free  from  iron,  byn!lretof 
ferrocyanuret  of  potassium,  and  then  washing  and  drying  the  preci- 
pitate. It  is  a white,  tasteless  powder,  is  insoluble  in  dilute  acids, 

and  contains  2 eq.  of  ferrocyanogen,  1 eq.  potassium,  3 eq.  of  zinc, 

and  12  eq.  of  water  =-2Cfy  -j-  j j -j-  12  aq.  A blue  tint 

shows  the  presence  of  Prussian  blue.  It  is  used  in  medicine. 

1823.  Ferrid-cyanogen.  By  treating  a solution  of  ferrocyanuret  Ferrid-cya- 
of  potassium  with  chlorine  a new  compound  of  potassium  is  formed,  nogen‘ 
the  radical  of  which  contains  twice  as  much  cyanogen  and  iron  as 

exists  in  ferrocyanogen.  It  may  be  called  ferrid-cyanogen  ; it 
unites  with  3 eq.  of  hydrogen  and  forms  a tribasic  acid. 

Its  formula  is  6Cy+2Fe ; symb.=Cfdy  ; ec[.  =214. 34. 

The  formula  of  hydro-ferridcyanic  acid  is  - Cfdy  + 3H 

ferridcyanuret  of  potassium  - - Cfdy  + 3K 

ferridcyanuret  of  iron  (Prussian  blue)  Cfdy  + 3Fe 

1824.  Hydro-ferridcyanic  Acid  unites  with  metallic  oxides,  form-  Hydro-fer 
ing  wrater  and  a metallic  ferridcyanuret;  of  these  the  compounds  ^^ancf 
with  the  metals  of  the  alkaline  earths*  as  also  that  corresponding  to  metallic 
the  peroxide  of  iron,  are  soluble  in  water ; all  others  are  insoluble  oxides. 


* Two  eq.  ferrocyanuret  of  potassium  and  iron  contain  1 eq.  of  ferrocyanuret  of  po- 
tassium and  3 eq.  of  ferrocyanuret  of  iron  (6Fe+3Cfy) ; of  these  6 eq.  of  iron,  2 are 
converted  into  peroxide  by  the  absorption  of  oxygen,  and  the  ferrocyanuret  of  potassi- 
um is  dissolved*  so  that  the  soluble  blue  compound  must  be  represented  by  the 

formula  j 2p®|os  \ + 3 Cfy,  which  corresponds  to  a compound  of  L eq.  of  Prussian 
blue  and  1 eq.  of  peroxide  of  iron. 

t If,  instead  of  the  salt  of  peroxide  of  iron,  the  ferrocyanuret  of  potassium  be  in  ex- 
cess, the  precipitate  is  likewise  blue,  but  it  is  a mixture  of  Prussian  blue  with  a com-* 
pound  composed  of  Prussian  blue  and  ferrocyanuret  of  potasssium  eq.  to  eq.  2Cfy-}- 

^■e2  ^ . On  washing,  the  latter  is  dissolved,  giving  a deep  blue  solution,  which  may 

be  evaporated  without  decomposition,  when  it  is  obtained  as  a deep  blue  mass  pos- 
sessed of  a strong  lustre-  It  is  precipitated  by  the  addition  of  a salt  to  its  solution, 
without  however  losing  its  solubility  in  pure  water;  it  is  distinguished  from  the  solu- 
ble basic  Prussian  blue  by  being  precipitated  from  its  solution  by  alcohol. 

53 


418 


Chap.  VI. 


Ferridcya- 
nuret  oi 
potassium. 


Properties. 


Ferrid-cya- 
nuret  of 
iron. 


Turnbull's 

blue. 


Constitu- 
tion of  the 
ferrocyanu 
rets  accor- 
ding to 
Berzelius, 


According 
to  Graham, 


Cyanogen  and  its  Compounds . 

in  water.  The  latter  may  be  prepared  by  the  mutual  decomposition 
of  a soluble  ferrideyanuret  and  the  corresponding  metallic  salt. 

1825.  Ferrideyanuret  of  Potassium.  K3Cfdy;  eq.=331.79.  Dis- 
covered by  L.  Gmelin,  is  prepared  by  passing  a stream  of  chlorine 
gas  through  a solution  of  ferrocyanuret  of  potassium,  until  it  no 
longer  gives  a blue  precipitate  with  salts  of  the  peroxide  of  iron  ; the 
solution  is  then  evaporated,  and  the  crystals  obtained  by  cooling  pu- 
rified from  the  admixture  of  chloride  of  potassium  by  re-crystalliza- 
tion.* 

1826.  They  are  transparent  right  rhombic  prisms  of  a red  colour 
and  high  lustre,  anhydrous,  permanent  in  the  air,  and  soluble  in  3.8 
parts  of  cold,  but  more  freely  in  hot  water;  burn  when  held  in  the 
flame  of  a candle  with  brilliant  scintillations  ; heated  in  close  ves- 
sels, cyanogen  and  nitrogen  gases  are  evolved,  a mixture  of  carburet 
of  iron  and  ferrocyanuret  of  potassium  is  the  residue.  The  aqueous 
solution  is  decomposed  by  hydrochloric  or  sulphuric  acid  ; in  the  last 
case,  sulphur  and  cyanuret  of  iron  are  precipitated,  and  ferrocyanu- 
ret of  potassium  and  prussic  acid  are  formed.  It  is  one  of  the  most 
delicate  tests  for  the  protoxide  of  iron,  with  which  it  forms  a precipi- 
tate similar  to  Prussian  blue  ; peroxide  of  iron  is  not  precipitated. 

1827.  Ferrideyanuret  of  Iron.  This  compound  is  likewise  sold 
in  commerce  as  Prussian  blue,  but  it  is  of  a lighter  colour  and  differs 
from  it  altogether  in  constitution.  It  is  prepared  by  precipitating 
a solution  of  the  protosulphate  of  iron  by  ferrideyanuret  of  potassium, 
or  by  a mixture  of  ferrocyanuret  of  potassium  and  hypochlorite  of 
soda,  to  which  a certain  quantity  of  hydrochloric  acid  has  been  ad- 
ded. In  this  kind  of  Prussian  blue  the  three  equivalents  of  potassi- 
um of  the  ferrideyanuret  of  potassium  are  replaced  by  3 eq.  of  iron. 

1828.  The  peculiarly  beautiful  Prussian  blue  sold  in  commerce 
under  the  name  of  Turnbull’s  blue,  is  the  ferrideyanuret  of  iron  ; it 
is  easily  recognised  by  its  action  on  ferrocyanuret  of  potassium,  for 
being  boiled  in  a solution  of  the  latter  it  is  decomposed  into  ferrid- 
eyanuret of  potassium,  which  is  dissolved,  and  into  an  insoluble  gray 
residue  of  ferrocyanuret  of  iron  and  ferrocyanuret  of  potassium. t 

1829.  According  to  Berzelius,  the  cyanurets  form,  by  uniting  with 
each  other,  double  compounds  similar  to  the  double  salts,  which  are 
produced  by  the  oxacids;  in  these  compounds,  therefore,  1 eq.  of 
cyanuret  of  iron  is  united  with  2 eq.  of  another  cyanuret,  the  consti- 
tution being  such,  if  the  metals  be  considered  united  with  oxygen,  as 
would  be  expressed  by  saying  that  the  oxygen  in  the  protoxide  of 
iron  is  equal  to  one  half  that  in  the  other  metallic  oxides. 

1S30.  According  to  Graham,  the  ferrocyanurets  are  formed  from  a 
peculiar  acid,  the  eq.  of  which  is  triple  of  that  of  the  hydrocyanic 
acid  ; it  contains  3 eq.  of  cyanogen,  which  constitutes  a radical 
called  prussine  in  combination  with  3 eq.  of  hydrogen.  This  acid  is 
accordingly  a tribasic  hydracid  corresponding  to  the  cyanuric  acid; 
in  uniting  with  a metallic  oxide  three  eq.  of  hydrogen  are  replaced 
by  their  eq.  of  the  metals. 


♦ Its  formation  is  owing  to  the  decomposition  of  2 eq,  of  ferrocyanuret  of  potassium, 
2 Cfy  4-  4 K,  by  1.  eq.  of  chlorine  into  L eq.  of  ferrideyanuret,  Cfdy  + 3 K,  and  1 eq. 
of  chloride  of  potassium,  KC1. 

t Cambell.  For  Cobalto- Cyanurets,  see  T.  and  L.  Elem.  786. 


419 


Iodide  of  Cyanogen. 

1331.  Chloride  of  Cyanogen.  Two  compounds  of  chlorine  with  Sect,  m. 
cyanogen  are  known,  and  these  are  isomeric  in  their  constitution.  Chloride  of 
The  one,  which  at  common  temperatures  is  gaseous,  was  discovered  Cyanogen, 
by  Gay-Lussac;  the  other,  which  is  a crystalline  solid,  by  Serullas. 

1832.  Gaseous  Chloride  of  Cyanogen , CyCl  ? is  formed  when  Gaseous 
chlorine  gas  is  transmitted  into  hydrated  prussic  acid,  when  moist  gJJnogen*' 
bicyanuret  is  placed  in  an  atmosphere  of  chlorine  in  the  dark,  or 

when  mellon  is  heated  in  dry  chlorine  gas. 

1833.  This  compound,  which  is  gaseous  at  common  temperatures,  Pr°P®rfies» 
has  a most  powerful  penetrating  odour,  excites  the  eyes  to  a copious 

flow  of  tears,  becomes  solid  at  0°,  and  forms  long  acicular  needles, 
which  fuse  at  5°  and  boil  at  10° ; but,  under  a pressure  of  four  at- 
mospheres, it  is  still  liquid  at  70.°  If  the  liquid  be  introduced  into 
glass  tubes  and  hermetically  sealed,  it  is  gradually  converted  into 
the  solid  chloride,  and  regular  crystals  of  the  following  compound 
aie  obtained. 

1834.  Water  dissolves  25,  alcohol  100,  and  ether  50  times  its  vo-  Action^f 
lume  of  the  gas  without  change.  It  is  decomposed  by  the  alkalies  ; e * 
salts  of  the  protoxide  of  iron  are  rendered  of  a deep  green  colour 

when  an  alkajj  is  added  to  the  mixture. 

1835.  If  moistened  bicyanuret  of  mercury  in  chlorine  gas  be  ex-  Of  light, 
posed  to  solar  light,  a heavy  oily  liquid  of  a yellow  colour  is  formed, 
which  is  insoluble  in  water,  and  has  the  same  odour  as  the  gaseous: 
chloride  ; the  same  substance  appears  to  be  formed  by  the  action  of 
chlorine  upon  the  fulminate  of  silver.  If  it  be  dissolved  in  alcohol;,. 

and  its  solution  thrown  into  water,  a crystalline  substance  like  cam- 
phor is  precipitated  ; on  exposing  a mixture  of  moist  chlorine  and 
chloride  of  cyanogen  gases  to  the  sun’s  rays,  two  other  solid  corn?* 
pounds  appear  to  be  formed. 

1836.  Solid  Chloride  of  Cyanogen.  Discovered  by  Serullas.  It  SoHdehlo- 
is  formed  by  exposing  dry  chlorine  gas  and  anhydrous  hydrocyanic  noggn.  °y 
acid  to  the  sun’s  light;  hydrochloric  acid  and  the  solid  chloride, 

which  is  deposited  in  crystals,  are  formed.  It  may  also  be  formed 
by  heating  sulphocyanuret  of  potassium  in  a stream  of  dry  chloriiip , 
gas. 

1837.  In  the  pure  state  it  is  white,  sublimes  in  long  transparent. Properties, 
crystals,  has  a penetrating  odour  similar  to  the  excrement  of  mice, 

and  a sweet  biting  taste;  its  sp.  gr.=1.32  ; fuses  at  284°,  sublimes 
at  374°.  By  digestion  in  water  at  a gentle  heat,  it  is  decomposed 
into  cyanuric  and  hydrochloric  acids,  from  which  its  constitution 
must  be  represented  by  the  formula  Cy3Cl3.  It  is  soluble  in  absolute 
alcohol  and  ether  without  decomposition. 

1838.  Iodide  of  Cyanogen.  Cyl.  Formed  by  heating  dry  cyanuret  Iodide  of 
of  mercury  or  silver  with  iodine;^  most  conveniently  by  heating  a cyanoSen‘ 
mixture  of  bicyanuret  of  mercury,  iodine,  and  water,  in  a retort,! 

when  at  a gentle  temperature  the  iodide  sublimes,  and  collects  in 
the  neck  of  the  retort  as  a fine  crystalline  snow,  or  in  long  needles. 

The  crystals  have  a penetrating  odour,  which  excites  a flow  of  tears, 
may  be  dissolved  in  alcohol,  ether,  and  water  without  decomposition, 
and  are  perfectly  volatilized  at  100°. 


* Wohler. 


t Mitscherlich. 


420 


Cyanogen  and  its  Compounds. 


Chap.  VI. 
Cyanogen 
phur. 


Hydrosul- 

phocyanic 

acid. 

Obtained. 


Properties 


Sulphocy- 
anurct  of 
ammoni- 
um.* 


Metallic 

sulphocya- 

nurets. 


1839.  Cyanogen  and  Sulphur . — Sulpho-cyanogen , Bisulphuret  of 
Cyanogen.  Cy-f-2S,  Symb.=Csy ; eq.=58.59.  Discovered  by  Lie- 
big. Prepared  by  saturating  a concentrated  solution  of  a metallic  sul- 
phocyanuret  with  chlorine,  or  by  heating  it  with  nitric  acid  ; it  falls  in 
the  form  of  a deep  yellow,  amorphous  powder,  which  retains  its  colour 
when  dry  ; is  light,  porous  ; is  insoluble  in  water,  alcohol,  and  ether, 
but  is  dissolved  by  strong  sulphuric  acid  from  which  it  is  precipitated 
by  water.  It  is  decomposed  by  nitric  acid  and  by  potassium  with  the  aid 
of  heat,  giving  rise  to  the  formation  of  the  sulphuret,  cyanuret,  and 
sulphocyanuret  of  potassium.  Its  decomposition  by  the  action  of 
heat  is  peculiarly  remarkable,  the  products  of  its  destructive  distilla- 
tion being  sulphuret  of  carbon,  sulphur,  and  the  residue  mellon, 
which  at  a high  temperature  is  decomposed  into  nitrogen  and  cyano- 
gen gases. 

1540.  Hydro-sulphocyanic  Acid.  Csy-|-H,  eq.  59.53.  Discover- 
ed by  Rink.  Occurs  in  the  seeds  and  blossoms  of  the  Cruciferse  (Se- 
napis,  &c.),  and  in  the  saliva  of  man  and  sheep. 

1541.  By  decomposing  the  basic  sulphocyanuret  of  lead  by  dilute 
sulphuric  acid,  care  being  taken  to  leave  some  lead  in  the  solution, 
which  is  afterwards  separated  by  hydrosulphuric  acid  gas;  or  by 
decomposing  sulphocyanuret  of  silver  in  10  volumes  of  water  by  the 
same  gas. 

1842.  A colourless  fluid  of  a pure  acid  taste,  which  by  the  action 
of  the  air,  and  on  being  heated,  readily  decomposes  into  a variety  of 
products;  one  of  these  deposits  itself  from  the  acid  as  a lemon-yel- 
low, in  water  insoluble,  powder.  It  cannot  exist  without  water;  on 
treating  the  aqueous  acid  with  chlorine  or  nitric  acid,  it  is  deprived 
of  hydrogen,  and  sulpho-cyanogen  is  precipitated:  by  a further  ac- 
tion cyanic  and  sulphuric  acids  are  formed,  but  the  former  is  at  once 
decomposed  into  carbonic  acid  and  ammonia.  It  colours  the  salts  of 
peroxide  of  iron  blood-red,  and  is  not  poisonous. 

1843.  Hydro-sulphocyanic  Acid  and  Ammonia — Sulphocyanuret  of 
Ammonium.  NH4+CySa;  eq.=75  74.  By  saturating  the  acid 
with  ammonia  and  gently  evaporating,  a semi-fluid  saline  mass  is 
obtained,  which,  at  a higher  temperature,  suffers  a peculiar  decom- 
position. At  first,  ammoniacal  gas  is  evolved,  then  sulphuret  of 
carbon,  and  at  last  the  protosulphuret  of  ammonium  is  sublimed. 
The  residue,  when  the  heat  has  not  been  driven  too  far,  consists  of 
melam,  or  of  a mixture  of  melam  with  mellon. 

Sulphocyanuret  of  ammonium  is  also  formed  by  adding  sulphuret 
of  carbon  to  alcohol,  which  has  been  saturated  with  ammonia. 

1844.  Metallic  sulphocyanurets.  The  hydro-sulphocyanic  acid 
must  be  considered  as  a compound  analogous  in  its  constitution  to 
the  hydrated  cyanic  acid,  the  oxygen  of  the  latter  having  been 
replaced  by  its  equivalent  of  sulphur.  Considered  as  a hydracid, 
the  formula  of  the  hydrated  cyanic  acid  would  be 

Cy02+H,  corresponding  to  that  of  the  hydro-sulpho- 
cyanic acid,  CySa-j-H. 

On  its  being  brought  into  contact  with  the  metallic  oxides,  the 
hydrogen  is  replaced  by  1 eq.  of  the  metal.  The  soluble  metallic 
sulphocyanuret  may  be  formed  : — by  the  action  of  the  acid  on  the 
metallic  oxide,  by  heating  the  higher  sulphurets  of  the  alkaline  me- 


421 


Cyanogen  and  Water . 

tals  to  redness  in  cyanogen  gas,  or  by  conducting  cyanogen  gas  into  Sect,  hi. 
their  solution,  by  heating  or  fusing  the  soluble  metallic  cyanurets 
with  sulphur,  or  the  insoluble  cyanurets  with  the  soluble  sulphuret. 

1845.  The  soluble  metallic  sulphocyanurets  colour  the  salts  °f  ofsofubl? 
peroxide  of  iron  blood-red  ; are  decomposed,  when  heated  in  dry  metaiiic 
hydrochloric  acid  gas,  into  metallic  chlorides  and  anhydrous  hydro-  sulphocya- 
sulphocyanic  acid,  but  the  latter  instantly  decomposes  into  other  pro-  nurets- 
ducts.  The  sulphocyanurets  of  the  alkaline  metals,  when  dry,  bear 

a strong  heat  without  decomposition,  but,  if  oxygen  be  present,  they 
are  converted,  with  the  evolution  of  sulphurous  acid,  into  salts  of 
cyanic  and  sulphuric  acids ; those  of  the  heavy  metals  are  decom- 
posed by  the  red  heat  into  mixtures  of  metallic  sulphurets  and  mel- 
lon,  this  change  being  generally  accompanied  by  the  evolution  of 
sulphuret  of  carbon  and  sulphur  ; at  a higher  temperature  the  resi- 
due evolves  cyanogen  and  nitrogen  gases  in  the  proportion  of  3 : 1. 

Heated  to  redness  in  chlorine  gas,  they  give  rise  to  metallic  chlo-  Action  of 
rides,  mellon,  chlorides  of  sulphur  and  cyanogen,  and  a small  quan- 
tity of  the  sulphuret  sublimes  unchanged  ; they  are  most  of  them 
soluble  in  alcohol.  The  proto-salts  of  mercury  are  decomposed  by 
the  soluble  sulphocyanurets  into  metallic  mercury  which  is  deposi- 
ted, and  into  the  soluble  bisulphocyanuret.  All  the  soluble  sulpho- 
cyanurets  form  with  the  bicyanuret  of  mercury  double  compounds, 
which  are  readily  obtained  in  crystals. 

1846.  Sulpkocyanuret  of  Potassium.  KCsy ; eq.  97.74.  Fer-  nuretY* 
rocyanuret  of  potassium,  gently  roasted  to  drive  off  water  of  crystal-  potassium, 
lization,  is  mixed  in  the  form  of  a fine  powder  with  half  its  weight 

of  flowers  of  sulphur,  and  the  mixture  fused  in  an  iron  vessel  at  a 
low  red  heat,  until  the  bubbles  of  gas  which  escape  through  the 
melted  mass  inflame  in  the  air  and  burn  with  a red  light.  The  mass 
when  cold  is  dissolved  in  boiling  water,  and  treated  with  a solution 
of  carbonate  of  potassa  as  long  as  a turbidity  is  produced  ; the  whole 
is  then  boiled  for  a quarter  of  an  hour,  and  the  clear  liquid  separated 
from  the  precipitated  iron  by  filtration.  On  evaporation  crystals  are 
obtained,  which  are  separated  from  the  admixture  of  carbonate  of 
potassa  by  being  re-dissolved  in  alcohol. 

1847.  Crystallizes  in  long  striated  colourless  prisms,  which  are  Properties, 
anhydrous,  of  a cooling,  somewhat  biting  taste,  fuse  much  below  the 

red  heat  to  a clear  liquid  ; deliquesces  in  a moist  atmosphere,  very 
soluble  in  hot  alcohol,  from  which  it  crystallizes  on  cooling.^ 

1848.  Cyanogen  and  Water.  A solution  of  cyanogen  in  water  ?ro^u^ts  of 

acquires  rapidly  in  the  light,  but  more  slowly  in  the  dark,  a brown  position 
colour,  and  a brown  flocculent  precipitate  falls  ; the  solution  is  then  cyanogen 
found  to  contain  carbonic  acid,  prussic  acid,  ammonia,  urea,  and  ox-andlts 
alate  ot  ammoma.T  pounds. 

1849.  The  different  products,  which  arise  from  the  reaction  of  cyanogen 
cyanogen  and  water,  are  without  doubt  the  results  of  several  perfectly  and  water, 
independent  decompositions.  One  eq.  of  cyanogen  and  3 eq.  water 
contain  the  elements  of  1 eq.  of  anhydrous  oxalate  of  ammonia  ; 2 

eq.  cyanogen  and  1 eq.  water,  the  elements  of  1 eq.  of  cyanic  and  1 
eq.  of  hydrocyanic  acid.  Carbonate  of  ammonia  is  formed  from  the 


* For  others,  see  T.  and  L.  794. 


+ Wohler. 


422 


Chap.  VI. 


Cyanogen 
and  ammo- 
nia. 


Paracyan- 

ogen. 


Cyanilic 

acid. 


Cyanogen 
and  hydro- 
sulphuric 
acid 


Prepared. 


Properties, 


Hydrosul- 
phocyanic 
acid  and 
hydrosul- 
phuric acid 


Cyanogen  and  its  Compounds . 

decomposition  of  cyanic  acid,  and  three  equivalents  of  water ; urea, 
by  the  union  of  cyanic  acid  with  ammonia  and  water. 

1850.  Cyanogen  and  Ammonia.  If  cyanogen  gas  be  conducted 
into  liquid  ammonia,  a decomposition  similar  to  that  produced  by 
water  ensues,  but  in  a much  shorter  time.  A large  quantity  of  a 
brown  substance,  which  contains  ammonia  in  chemical  combination, 
is  deposited. 

By  heating  this  brown  precipitate  to  redness,  paracyanogen,  water, 
and  carbonate  of  ammonia  are  obtained ; this  decomposition  is  rea- 
dily explained,  when  it  is  considered  that  this  product  may  be  con- 
sidered as  a compound  of  cyanogen  (C4N2)  with  ammonia  and  cyanic 
acid  ; the  latter  of  which,  by  decomposing  with  3 eq.  water,  forms  2 
eq.  of  carbonic  acid  and  1 eq.  of  ammonia. 

1851.  Paracyanogen.  Discovered  by  Johnston.  Formed  by 
heating  to  redness  the  brown  precipitate  formed  by  the  decomposi- 
tion of  cyanogen  with  water  or  ammonia  ; left  in  small  quantity  on 
decomposing  bicyanuret  of  mercury  in  a retort  by  heat.* 

1852.  Cyanilic  Acid.  By  a long-continued  boiling  of  mellon  in 
dilute  nitric  acid,  a solution  is  effected  with  the  evolution  of  gaseous 
products,  and  the  liquid  yields  on  evaporation  colourless, transparent, 
octohedral  crystals  ; by  resolution  in  hot  water,  hydrated  cyanilic 
acid  in  soft  tabular  crystals  of  a mother-of-pearl  lustre  are  obtained. 
This  acid  has  the  same  composition  as  the  crystalline  cyanuric  acid  ; 
contains,  like  the  latter,  4 eq.  water  of  crystallization,  which  it  loses 
at  212°,  when  it  becomes  opaque  and  falls  to  a white  powder.  By 
the  destructive  distillation  it  is  converted  into  hydrated  cyanic  acid  ; 
by  solution  in  sulphuric  acid  and  caustic  potassa  into  cyanuric  acid. 

1853.  Cyanogen  and  Hydro  sulphuric  Acid.  Cy3S0H6  -f-  aq. 
Two  compounds  of  cyanogen  and  hydrosulphuric  acid  are  known, 
neither  of  which  are  formed  when  the  gases  are  mixed  in  a dry  state, 
but  are  generated  by  the  direct  combination  of  the  gases  when  water 
is  present.  The  one  discovered  by  Gay-Lussac  is  obtained  by  mix- 
ing one  volume  of  cyanogen  with  one  and  a half  volume  of  sulphu- 
retted hydrogen,  a small  quantity  of  water  being  present;  both  the 
gases  are  absorbed  by  the  water,  and  on  evaporation  it  deposits  long 
yellow  acicular  crystals,  a solution  of  which  is  not  precipitated  by 
salts  of  lead.  The  other  compound  was  discovered  by  Wohler. 

It  is  prepared  by  conducting  sulphuretted  hydrogen  into  a saturated  solution  of 
cyanogen  in  alcohol,  by  which  the  latter  is  rendered  yellow,  and  on  being  artifi- 
cially cooled  deposits  this  compound  of  cyanogen  and  sulphuretted  hydrogen  in 
bright  orange-red  crystals. 

1854.  Insoluble  in  cold,  slightly  soluble  in  boiling  water.  Very 
soluble  in  hot  alcohol,  from  which  it  may  again  be  obtained  in  crys- 
tals ; soluble  by  alkalies  in  the  cold,  and  precipitated  unchanged  from 
the  solution  by  acids  ; but  on  the  application  of  heat  a mixture  of  a 
metallic  sulphuret  and  a sulphocyanuret  is  formed  ; its  solution  pre- 
cipitates salts  of  silver,  lead,  and  copper. 

1S55.  Hydro-sulphocyanic  Acid  arid  Hydrosulphuric  Acid.  Dis- 
covered by  Zeise.  Prepared  by  saturating  1 volume  of  absolute 
alcohol  at  the  temperature  of  50°  with  ammoniacal  gas,  and  adding 


♦For  products  of  the  decomposition  of  sulphocyanogen,  mellon  (1726),  hydromello- 
nic  acid,  &c.  see  T.  and  L.  Elem.  796. 


Uric  Acid. 


423 


to  the  solution  a mixture  of  0.16  vol.  of  bisulphuret  of  carbon,  and  Sect,  iv. 
0.4  vol.  of  alcohol ; the  whole  should  be  placed  in  a well-stopped 
glass  vessel,  which  is  kept  perfectly  full  at  the  temperature  of  60°. 

Two  products  are  thus  produced,  of  which  the  one  is  a compound  of 
ammonia  with  an  acid  formed  of  sulphuret  of  carbon  and  sulphuret- 
ted hydrogen;  this  ammoniacal  salt  separates  in  the  course  of  some 
hours  as  a crystalline  deposit,  and  the  residual  liquid  contains  ano- 
ther ammoniacal  salt,  the  acid  of  which  may  be  considered  as  a 
compound  of  hydro-sulphocyanic  acid  and  hydro-sulphuric  acid. 


Section  IV.  Hypothetical  Compounds  of  Cyanogen  and  Carbonic 

Oxide . 


1856.  Under  these  compounds  the  uric  acid  and  the  products  of^|P^eti‘ 
its  decomposition  are  described.  These  substances  are  distinctly  pounds  of 
separated  from  all  known  bodies  by  their  chemical  relations  ; an  cyanogen 
explanation  of  their  formation  can  only  be  developed  by  making  cer-  ^ic  oxides", 
tain  hypotheses,  of  which  the  assumption  that  they  contain  cyanogen 

and  carbonic  oxide  is  a deduction  drawn  from  their  analyses.  The 
compounds  belonging  to  this  group  are  uril,  uric  acid,  alloxan,  al- 
loxantin, and  uramil.  (Liebig,  so4.) 

1857.  The  uril,  or  urilic  acid,  which  may  from  its  composition  be  Uril* 
also  called  the  cyan-oxalic  acid,  is  an  hypothetical  compound  of  ni- 
trogen, carbon,  and  oxygen,  according  to  the  formula  C8N204 ; it 
may  be  considered  as  a compound  of  cyanogen  and  carbonic  oxide 
2Cy-(-4CO,  or  as  oxalic  acid,  in  which  the  oxygen  which  unites  with 

the  radical,  carbonic  oxide,  has  been  replaced  by  its  eq.  of  cyanogen. 

C202  -f-0  . . . Oxalic  acid. 

2(C202-f-Cy)  . . . Cyan-oxalic  acid. 

If  this  acid  be  represented  by  the  symbol  Ul,  the  compounds  are 
represented  by  the  formula : 


Rational  formula. 

2U1+1  eq.  urea  . =Uric  acid 
2UI-f  OM-4  aq.  . = Alloxan 

2Ul-fO  +5  aq.  . = Alloxantin 

2U1-J-1  eq.  amm.-+2  aq.  =Uramil 


Empirical  formula. 

C10N4  H4  Oo 

Cs  N2  H4  Oie 
C8  N2  Hs  O10, 
Ci  N3  Hg  Og. 


1858.  Uric  Acid.  Ci0N4H4O(;,  or  2 Ul-f-(C202+2NH2).  Discover- Uric  acid, 
ed  by  Scheele  ; first  pointed  out  as  existing  in  the  excrement  of  snakes 

by  Vauquelin,  in  the  excrement  of  silkworms  by  Brugnatelli,  and  in 
cantharides  byRobiquet.  Is  a product  of  secretion  of  all  carnivorous 
animals,  of  birds,  and  of  many  insects  ; is  deposited  from  human 
urine  generally  in  combination  with  ammonia,  as  it  cools,  as  a yellow 
or  brownish  powder ; the  stone-like  concretions  in  the  joints  of  persons 
labouring  under  gout  contain  uric  acid  in  combination  with  soda 
or  ammonia  ; it  is  the  basis  of  most  calcareous  deposits  in  the  hu- 
man bladder.  The  semi-fluid  urine  of  serpents  and  birds  is  princi- 
pally composed  of  urate  of  ammonia.  The  guano  (the  decomposed  Guano, 
excrement  of  aquatic  birds,  which  covers  the  surface  of  many  of  the 
smaller  islands  of  the  South  Sea,  and  is  used  as  manure,)  is  also 
composed  in  greater  part  of  urate  of  ammonia. 

1859.  Urinary  calculi,  or  the  white  'chalk-like  excrement  of  ser-  Process. 


424 


Chap.  VI. 


Properties. 


Product  of 
destructive 
distillation. 


Action  ol 
nitric  acid. 


Uric  acid 
and  metal- 
lic oxides. 


Urate  of 
potassa. 


Urate  of 
soda. 


Hypothetical  Compounds  of  Cyanogen. 

pents,  is  reduced  to  a fine  powder  and  dissolved  in  a solution  of 
caustic  potassa  by  boiling  ; the  solution  is  treated  with  hydrochloric 
acid  in  excess,  boiled  for  one  quarter  of  an  hour,  and  the  precipitate 
well  washed.  It  is  obtained  perfectly  pure  by  decomposing  a satu- 
rated boiling  solution  of  urate  of  potassa  by  hydrochloric  acid. 

1860.  Crystallizes  in  fine  scales  of  a brilliant  white  colour  and 
silky  lustre,  is  tasteless  and  inodorous,  heavier  than  water,  almost  in- 
soluble in  cold,  slightly  soluble,  in  small  quantity,  in  boiling  water ; 
the  solution  reddens  feebly  the  vegetable  colours.  It  is  dissolved  by 
concentrated  sulphuric  acid,  from  which  it  is  precipitated  by  water  ; 
in  strong  hydrochloric  acid,  it  is  somewhat  more  soluble  than  in  pure 
water. 

1861.  Exposed  to  the  destructive  distillation,  the  products  of  the 
decomposition  of  urea  are  obtained,  namely,  urea,  cyanuric  acid,  and 
cyamelid  (the  insoluble  cyanuric  acid) ; also,  hydrocyanic  acid,  a 
litle  carbonate  of  ammonia,  and,  as  a residue,  a brown  carbonaceous 
substance  which  is  rich  in  nitrogen.  In  this  decomposition  the  hy- 
drated cyanic  acid  in  combination  with  ammonia  is  deposited  in  the 
neck  of  the  retort  as  urea  ; the  cyamelid  dissolved  in  potassa  forms 
cyanurate  of  potassa. 

1S62.  Dissolves  in  dilute  nitric  acid  with  the  evolution  of  equal 
volumes  of  pure  carbonic  acid  and  nitrogen ; the  solution  contains 
alloxan,  alloxantin,  parabanic  acid,  and  ammonia  ; evaporated  and 
treated  with  ammonia  in  excess,  it  acquires  a purple-red  colour,  a 
test  by  which  uric  acid  may  be  recognised.  Fused  with  hydrate  of  po- 
tassa, carbonic  acid,  and  cyanate  of  potassa,  and  cyanuret  of  potassium 
are  obtained  ; boiled  with  peroxide  of  lead  in  water,  it  is  decomposed 
into  allantoin  and  oxalic  acid,  and  urea  is  separated.  Is  insoluble 
in  ether  and  alcohol.  With  sulphuric  acid  it  forms  a crystalline 
compound.* 

1863.  Uric  Acid  and  the  Metallic  Oxides.  The  uric  acid  appears 
to  unite  with  the  metallic  oxides  without,  as  in  the  other  acids,  the 
separation  of  an  eq.  of  water ; its  salts,  with  the  fixed  alkalies  and 
alkaline  earths,  are  sparingly  dissolved  by  cold,  but  more  freely  by 
boiling  water;  with  ammonia  and  the  other  oxides,  insoluble  com- 
pounds, generally  of  a white  colour,  are  formed.  All  urates  are  de- 
composed by  other  acids,  even  by  acetic  acid  ; the  uric  acid  is  at  first 
separated  as  a bulky  gelatinous  mass,  but  it  shortly  afterwards  chan- 
ges into  a fine  crystalline  powder. 

1864.  Urate  of  Potassa.  Impure  urate  of  ammonia  (the  excre- 
ment of  serpents)  is  dissolved  by  boiling  in  a dilute  solution  of  caus- 
tic potassa ; and  the  clear  liquid,  obtained  by  separating  the  insolu- 
ble portions  by  filtration,  is  evaporated.  On  cooling,  the  urate  of 
potassa  separates  as  a white  crystalline  mass,  which,  when  washed 
by  cold  water  and  dried,  yields  a powder  composed  of  fine  acicular 
crystals  of  a silky  lustre  ; these  crystals  are  very  sparingly  soluble  in 
cold  water,  and  the  alkaline  reaction  is  scarcely  perceptible.  Uric 
acid  is  more  soluble  in  carbonate  of  potassa  than  in  pure  water  ; and 
one  half  of  the  carbonate  is  decomposed. 

1S65.  Urate  of  Soda.  The  action  of  uric  acid  upon  pure  and 
carbonate  of  soda  is  the  same  as  above  described  for  potassa ; this 


Fntszche. 


Alloxan . 


425 


salt  may  also  be  formed  by  boiling  uric  acid  in  a solution  of  borax ; sect,  iv, 
it  is  the  principal  constituent  of  gouty  concretions.^ 

1866.  Allantoin.  Frequently  called  allantoic  acid.  Occurs  ready  Allantoin. 
formed  in  the  allantoic  fluid  of  the  cow  ;t  it  is  formed  when  uric  acid 
is  boiled  in  water  with  peroxide  of  lead  ! 

One  part  of  uric  acid  is  boiled  in  20  parts  of  water,  and  recently  prepared  and  Process, 
well- washed  peroxide  of  lead  is  added  in  successive  portions  to  the  boiling  liquid 
as  long  as  its  colour  is  observed  to  change.  The  hot  liquid  should  be  filtered, 
and  evaporated  until  crystals  are  observed  to  form  upon  its  surface.  The  crys- 
tals which  have  deposited  when  the  solution  has  become  quite  cold,  are  purified 
by  recrystallization.  Or  the  allantoic  fluid  of  the  cow  may  be  evaporated  to  one 
quarter  its  volume,  and  the  crystals  formed  on  cooling  and  long  standing  are  pu- 
rified by  animal  charcoal. 


1867.  Small  transparent  and  colourless  prisms  of  the  right  rhom-  Properties, 
bic  system,  which  have  a.  glassy  lustre,  are  tasteless,  have  no  action 

on  vegetable  colours,  and  are  soluble  in  160  parts  of  cold,  but  more 
freely  in  hot  water.  It  is  soluble  in  nitric  acid,  and  is  decomposed 
by  it  when  the  solution  is  boiled  without  the  evolution  of  nitrous 
fumes.  Its  composition  is  such,  that  it  contains  the  elements  of  an- 
hydrous oxalate  of  ammonia  minus  3 eq.  water  ; this  explains  its  de- 
composition by  the  alkalies,  by  which  it  is  reduced  at  the  boiling 
heat  into  an  oxalate  and  ammonia. 

1868.  Gently  heated  in  concentrated  sulphuric  acid,  it  is  decom-  Action  of 
posed  into  carbonic  oxide,  carbonic  acid  and  ammonia  ; but  if  a strong 

heat  be  rapidly  applied,  the  acid  is  blackened.  It  is  soluble  in  caus-  5 * 

tic  and  carbonated  alkalies  by  the  aid  of  a gentle  heat,  and  may  be 
again  obtained  unchanged  by  crystallization.  A solution  of  allan- 
toin in  hot  water,  to  which  a little  ammonia  has  been  added,  pro- 
duces, with  the  nitrate  of  silver,  a white  precipitate,  which  contains 
43,56  per  cent,  of  oxide  of  silver,  and  is  composed  as  represented  by 
the  formula,  CdN4H505-l-Ag0  ; it  consequently  contains  2 eq.  allan- 
toin, CsN4H606 — 1 eq.  water,  HO-f-1  eq.  oxide  of  silver. 

1869.  In  the  decomposition  of  uric  acid  by  the  peroxide  of  lead,  2 eq.  of  oxy-  Explained, 
gen  derived  from  2 eq.  of  the  peroxide,  and  3 eq.  water,  attach  themselves  to  the 
constituents  of  the  cyanoxalic  acid,  by  which  the  latter  is  decomposed  into  2 eq. 

oxalic  acid  and  1 eq.  allantoin,  and  the  urea  is  set  free. 

C404+N2C4_  ( 1 eq.  cyanoxalic  acid  ) , • •. 

2PbO+  02+H303—  X 1 eq.  urea $ ~ 1 e(*’  UnC  aclcL 

2 eq.  oxalate  of  lead+1  eq.  allantoin-fl  eq.  urea. 

Its  formula  is  C4  H3  N2  03,  or  2 Cy+3110. 


1870.  Alloxan.  The  erytbric  acid  of  Brugnatelli : rediscovered  Alloxan, 
by  Wohler  and  Liebig.  One  of  the  products  of  the  decomposition  of 
uric  acid  by  nitric  acid. 

One  part  of  dry  uric  acid  is  added  in  successive  portions  to  4 parts  of  process. 
nitric  acid  of  sp.  gr.  1.45  to  1.5,  by  which  it  is  dissolved  with  efferves- 
cence and  the  production  of  heat ; the,  production  of  a high  temperature 
must  be  avoided  as  much  as  possible  by  artificial  cooling,  and  by  adding  the  uric 
acid  slowly.  Small  granular  crystals  of  a strong  lustre  are  thus  formed,  and  by 
degrees  the  whole  liquid  is  converted  into  a solid  mass.  This  should  then  be 
placed  in  a glass  funnel ; and  after  the  fluid  parts  have  thus  drained  off,  it  should 
be  spread  upon  a porous  tile,  where  it  is  rendered  perfectly  dry.  It  is  purified 
by  solution  in  hot  water  and  recrystallization. 


1871.  On  the  cooling  of  a warm  but  not  perfectly  saturated  solu-  Properties. 


* Wollaston. 

54 


t Vauquelin  and  Buniva. 


t Wohler  and  Liebig. 


426 


Chap.  VI. 


Solubility. 


Action  of 
zinc,  fee* 


Theory. 


Alloxanic 

acid. 


Cyanogen  and  its  Compounds. 

tion  of  alloxan,  it  is  obtained  in  large  colourless  and  transparent  crys- 
tals of  the  right  prismatic  system,  and  of  a strong  adamantine  lustre  ; 
these  crystals  effloresce  rapidly,  losing  25  per  cent.=6  eq.  water, 
and  are  converted  when  gently  warmed,  with  the  loss  of  water,  into 
anhydrous  alloxan.  If  a hot  saturated  solution  be  allowed  to  crys- 
tallize in  a warm  place,  anhydrous  alloxan  is  deposited  directly  from 
the  solution  in  oblique  prisms,  on  the  extremities  of  which  truncated 
rhomboidal  octohedrons  are  seen. 

1872.  It  is  very  soluble  in  water,  has  a disagreeable  odour,  and  a 
slightly  saline  astringent  taste,  reddens  vegetable  colours,  and  causes 
a purple  stain  on  the  skin.  Treated  with  alkalies,  alloxanic  acid  is 
formed  ; but  on  boiling  it  is  decomposed  into  urea  and  mesoxalic 
acid.  Heated  with  peroxide  of  lead,  it  is  decomposed  into  urea  and 
carbonate  of  lead,  with  which  a few  traces  of  oxalate  of  lead  are 
mixed. 

1873.  When  brought  into  contact  with  zinc  and  hydrochloric  acid, 
with  chloride  of  zinc  or  sulphuretted  hydrogen,  alloxantin  is  produced ; 
it  is  decomposed  by  free  ammonia  into  mykomelinic  acid,  by  nitric 
acid  into  parabanic  acid,  by  sulphuric  and  hydrochloric  acids  into 
alloxantin,  by  sulphurous  acid  and  ammonia  into  thionurate  of  am- 
monia, with  alloxantin  and  ammonia  into  murexid.  With  a proto- 
salt  of  iron  and  an  alkali,  it  forms  an  indigo-blue  solution.  Does  not 
unite  without  decomposition  with  the  metallic  oxides. 

1874.  The  formation  of  alloxan  and  the  other  products  which  arise  at  the  same 
time,  is  dependent  upon  two  perfectly  independent  decompositions;  namely, 
upon  the  conversion  of  cyanoxalic  acid  into  alloxan,  and  upon  the  mutual  de- 
composition of  urea  and  hyponitrous  acid.  To  1 eq.  of  cyanoxalic  acid  are  added 
the  elements  of  4 eq.  water,  and  2 eq.  oxygen  from  1 eq.  nitric  acid,  by  which  1 
eq.  alloxan  and  1 eq.  hyponitrous  acid  are  formed.  The  latter  combines  with 
the  ammonia  of  the  urea,  and  liberates  cyanic  acid  ; the  hyponitrite  of  ammonia 
is  decomposed  by  heat  into  nitrogen  and  water,  and  the  cyanic  acid  with  water 
is  resolved  into  carbonic  acid  ana  ammonia,  which  unites  with  the  free  nitric 
acid. 

Cyanoxalic  acid=C8N2  04 
4 eq.  water  ~H404 

2 eq.  oxygen  02 

1 eq.  alloxan  = C8N2H4Oio 
Urea  =C2N2H402 

Hyponitrous  acid=  N 03 

c2n3h4o7=c2o4+  n2+  nh3+  ho 

Carbonic  acid.  Nitrogen.  Ammonia.  Water. 

It  frequently  happens  that  on  dissolving  the  impure  alloxan,  for 
the  purpose  of  purifying  by  a second  crystallization,  a portion  of 
alloxantin  is  obtained  ; it  may  be  easily  separated  from  the  alloxan- 
tin by  cold  water.  (See  Alloxantin.) 

1875.  Alloxanic  Acid.  CsN2H208-|-2  eq.  Discovered  by  Wohler 
and  Liebig.  Produced  by  the  decomposition  of  alloxan  by  alkalies. 
It  is  prepared  by  decomposing  alloxanate  of  baryta  by  sulphuric  acid. 
A strongly  acid  fluid  is  obtained,  which  by  gentle  evaporation  crys- 
tallizes in  radiated  groups  of  acicular  crystals ; it  is  a bibasic  acid, 
dissolves  zinc  with  the  evolution  of  hydrogen,  is  unchanged  by  sul- 
phuretted hydrogen,  and  precipitates  the  salts  of  silver,  baryta,  and 
lime.  The  anhydrous  alloxanic  acid  contains  the  constituents  of 
half  an  equivalent  of  alloxan  minus  1 eq.  water. 


427 


Mykomelinic  Acid. 

1876.  Alloxanic  acid  neutralizes  the  alkalies  perfectly,  decom-  Sect,  iv. 
poses  the  carbonates,  and  forms,  when  neutralized  by  ammonia,  with  Alloxanic 
the  salts  of  silver  a white  precipitate,  which  by  boiling  becomes  first 
yellow  and  then  black,  the  change  being  accompanied  by  a rapid  ef-  oxides. 
fervescence  ; treated  with  ammonia  in  excess,  it  produces  white  gela- 
tinous precipitates  with  the  salts  of  lime,  strontia,  and  baryta ; but 

the  precipitate  is  redissolved  by  a large  excess  of  water,  and  readily 
by  an  acid.  The  solutions  of  the  neutral  alloxanate  of  lime,  stron- 
tia, and  baryta,  become  turbid  when  boiled,  the  bases  are  precipitated, 
and  urea  and  mesoxalic  acid  are  formed.* 

1877.  Mesoxalic  Acid.  When  a saturated  solution  of  alloxanate  of  Mesoxalic 
baryta  or  strontia  is  heated  to  the  boiling  point,  a precipitate  falls  aci 
consisting  of  the  carbonate,  mesoxalate,  and  alloxanate  of  baryta  or 
strontia.  The  solution,  on  evaporation,  yields  a crystalline  crust, 

from  which  urea  is  separated  by  treating  it  with  alcohol,  and  mesox- 
alate of  baryta  remains.  If  a solution  of  alloxan  be  added,  drop  by 
drop,  to  a boiling  solution  of  acetate  of  lead,  a very  heavy  granular 
precipitate  of  mesoxalate  of  lead  is  formed,  and  urea  remains  as  the 
only  other  product  in  the  solution.  The  mesoxalic  acid  may  be  ob- 
tained by  decomposing  this  lead  salt  by  sulphuric  acid ; it  is  a 
strongly  acid  solution,  reddens  vegetable  colours,  and  forms,  like  the 
alloxanic  acid,  on  the  addition  of  ammonia,  precipitates  with  the 
salts  of  baryta  and  lime,  which  are  soluble  in  acids  and  a large  ex- 
cess of  water  ; it  may  be  boiled  and  evaporated  without  change.  Its 
action  on  the  salts  of  silver  is  characteristic  ; it  forms  with  them, 
after  being  neutralized  by  ammonia,  a yellow  precipitate,  which  on 
being  gently  heated  is  reduced  to  the  metal  with  a rapid  efferves- 
cence. 

1878.  The  above-mentioned  lead  salt  yields,  on  analysis,  80.4  percent,  of  oxide  of  Analysis 
lead  ; it  contains  a slight  admixture  of  a substance  containing  nitrogen,  probably  and  compo- 
cyanate  or  cyanurate  of  lead,  from  which  it  cannot  be  perfectly  purified.  The  sition. 
composition  of  the  lead  salt  is  very  probably  expressed  by  the  formula  C304+ 

2PbO,  in  which  case  its  formation  from  alloxan  and  alloxanic  acid  admits  of  a 
ready  explanation.  From  1 eq.  alloxan  1 eq.  urea  is  separated,  by  which  2 eq. 
of  anhydrous  mesoxalic  acid  is  left. 

1 eq.  alloxan  suCsN^H^Oio 

— 1 eq.  urea  — C 2 N2  H 4 O2 

=2  eq.  mesoxalic  acid  =Cg  Og 

The  above-mentioned  mesoxalate  of  baryta  contains  56  per  cent,  of  baryta, 
from  which  its  constitution  is  probably  represented  by  the  formula  C304-f  ^ 

1879.  Mykomelinic  Acid.  C8N4H505  ? Discovered  by  Wohler  Mykome- 
and  Liebig.  Product  of  the  decomposition  of  alloxan  by  ammonia.  linic  acid* 

It  is  prepared  by  heating  to  212°  a solution  of  alloxan  with  an  excess  of  ammo-  Process, 
nia,  then  neutralizing  with  an  excess  of  dilute  sulphuric  acid  and  boiling  for  a 
few  minutes.  The  mykomelinic  acid  falls  as  a yellow  gelatinous  precipitate, 
which  dries  to  a yellow  porous  powder;  it  is  with  difficulty  dissolved  by  cold, 
but  more  readily  by  hot  water. 

1880.  Its  solution  has  a distinctly  acid  reaction  ; it  decomposes 
the  carbonated  alkalies  and  is  easily  dissolved  by  the  caustic  alka- 
lies, but  on  being  boiled  with  them  is  decomposed  with  the  evolution 
of  ammonia  ; it  forms,  with  the  oxide  of  silver,  a yellow  compound, 


♦For  Alloxanates , see  T.  and  L.  810. 


428 


Cyanogen  and  its  Compounds. 


Chap.  VI. 


Parabanic 

acid. 


Properties. 


Theory. 


Oxaluric 

acid. 


Properties, 


Theory. 


Oxalurate 
of  ammo* 
nia. 

Process. 


which  is  insoluble  in  water.  It  is  produced  by  the  decomposition  of 

1 eq.  alloxan  and  2 eq.  ammonia  into  1 eq.  mykomelinic  acid  and  5 
eq.  water. 

1881.  Farabanic  Acid.  CGN204-|-2  aq.  Discovered  by  Wohler 
and  Liebig.  Product  of  the  decomposition  of  uric  acid  and  alloxan 
by  nitric  acid.  Prepared  by  treating  1 part  of  uric  acid,  or  1 part  of 
alloxan,  in  8 parts  of  pretty  strong  nitric  acid,  evaporating  to  the 
consistence  of  a syrup,  and  allowing  it  to  stand  for  some  time,  when 
it  yields  colourless  crystals  which  may  be  purified  by  a second  crys- 
tallization. 

1882.  Colourless,  transparent,  thin,  hexagonal  prisms;  has  a 
strong  acid  taste,  very  similar  to  that  of  oxalic  acid;  is  very  soluble 
in  water,  does  not  effloresce  either  in  the  air  or  in  a warm  room ; 
fuses  if  heated,  when  a portion  sublimes  unchanged,  but  another  part 
decomposes  with  the  evolution  of  hydrocyanic  acid.  The  cold  solu- 
tion neutralized  by  ammonia,  produces  a white  precipitate  in  the 
salts  of  silver,  which  contains  70.62  per  cent,  of  the  oxide  ; when 
treated  with  ammonia  it  is  converted  into  oxaluric  acid. 

1883.  It  is  formed  by  the  decomposition  of  1 eq.  of  uric  acid, 
which,  by  the  addition  of  2 eq.  of  water  and  4 eq.  oxygen  from  the 
nitric  acid,  is  resolved  into  2 eq.  carbonic  acid,  1 eq.  parabanic  acid, 
and  1 eq.  urea  ; the  latter  is  decomposed  as  before-mentioned  by  the 
hyponitrous  acid.  One  eq.  alloxan  with  2 eq.  oxygen  is  resolved  into 

2 eq.  carbonic  acid,  4 eq.  water,  and  1 eq.  parabanic  acid. 

1SS4.  Oxaluric  Acid.  CflN2H,}07-(-aq.  Discovered  by  Wohler  and 
Liebig.  Produced  by  the  decomposition  of  parabanic  acid. 

Prepared  by  adding  dilute  sulphuric  or  hydrochloric  acid  to  a saturated  solu- 
tion of  oxalurate  of  ammonia  in  not  water,  and  rapidly  cooling  the  mixture  when 
the  oxaluric  acid  falls  as  a white  crystalline  powder;  this  should  be  washed  with 
cold  water  as  long  as  the  washing,  when  neutralized  by  ammonia,  causes  with 
the  salts  of  lime  a precipitate  which  is  perfectly  redissolved  by  heat,  or  by  an  ad- 
ditional quantity  of  water. 

18S-5.  It  is  a white,  or  slightly  yellow  crystalline  powder  of  an 
acid  taste,  reddens  the  vegetable  colours,  and,  when  neutralized  hy 
ammonia,  forms  with  silver  salts  a white  precipitate  which  is  per- 
fectly redissolved  by  boiling.  By  boiling  in  water  it  is  completely 
decomposed  into  free  oxalic  acid  and  oxalate  of  urea. 

1886.  The  oxaluric  acid  is  formed  bv  the  addition  of2  eq.  water  to  the  consti- 
tuents of  the  parabanic  acid.  It  contains  further  the  elements  of  2 equivalents  of 
oxalic  acid  and  1 eq.  urea ; it  may  be  considered  as  uric  acid  in  which  the  cya- 
noxalic  acid  has  been  replaced  by  the  oxalic  acid. 

1887.  Oxalurate  of  Ammonia , NH40-|-C6N2H.i07,  may  be  formed 

by  heating  a solution  of  parabanic  acid  with  ammonia,  or  more  advantageously 
by  treating  a recently  prepared  solution  of  uric  acid  in  dilute  nitric  acid  with  an 
excess  of  ammonia  and  evaporating.  The  liquid  acquires  at  first  a purple  colour, 
which  disappears  during  the  evaporation,  and  if  allowed  to  cool  when  arrived  at 
a certain  degree  of  concentration,  it  deposits  radiated  groups  of  hard  acicular  yel- 
low crystals ; they  are  obtained  colourless  by  charcoal  and  recrystallization. 


Properties.  1888.  The  oxalurate  of  ammonia  crystallizes  in  radiated  groups 
of  fine  acicular  crystals,  which  have  a silky  lustre,  and  are  readily 
dissolved  by  hot,  but  with  difficulty  by  cold  water;  the  solution  has 
no  reaction  on  vegetable  colours,  and  may  be  boiled  and  evaporated 
without  change  ; the  dry  salt  loses  no  weight  at  250°,  but  at  a higher 


Uramil. 


429 


temperature  it  is  decomposed  with  the  rapid  evolution  of  hydrocya-  Sect,  tv. 
nic  acid.  Acids  separate  from  a concentrated  solution  the  oxaluric 
acid  as  a crystalline  powder. 

1889.  The  oxaluric  acid  forms  with  the  alkalies  very  soluble,  but  Oxaluric 
with  the  alkaline  earths  sparingly  soluble  salts.  If  concentrated  so-  aad 
lutions  of  oxalurate  of  ammonia,  chloride  of  calcium  or  barium  be  ^dgS|c 
mixed  with  each  other,  after  standing  some  time,  brilliant  transpa- 
rent scales  or  needles  of  oxalurate  of  baryta  or  lime  will  be  deposited  ; 

a solution  of  the  latter  in  water  when  treated  with  an  excess  of  am- 
monia gives  a basic  salt  in  the  form  of  a transparent  gelatinous  pre- 
cipitate, which  is  redissolved  by  a large  quantity  of  water. 

1890.  Thionuric  Acid.  C8N3H7014S2.  A bibasic  acid.  Discovered  Thionuric 
by  Wohler  and  Liebig.  Is  formed  by  the  action  of  sulphurous  ac‘d- 
acid  on  alloxan.  It  is  prepared  by  decomposing  the  thionurate  of 

lead  by  hydrosulphuric  acid.  A white  crystalline  mass,  is  perma- 
nent in  the  air,  and  readily  dissolved  by  water  ; of  an  acid  taste, 
reddens  vegetable  blues  strongly;  its  saturated  solution,  when 
heated  to  the  boiling  point,  congeals  to  a semi-fluid  crystalline  mass 
of  uramil,  and  the  fluid  when  this  has  deposited  is  found  to  contain 
free  sulphuric  acid. 

1S91.  The  thionuric  acid  contains  the  elements  of  1 eq.  alloxan,  Theory. 

1 eq.  ammonia,  and  2 eq.  sulphurous  acid  ; the  uramil  may  be  con- 
sidered as  a compound  of  ammonia  with  alloxan  minus  2 eq.  oxygen, 
or  of  cyanoxalic  acid  with  1 eq.  ammonia  and  2 eq.  water.  On 
heating  the  solution  of  thionuric  acid  2 eq.  oxygen  are  given  by  1 
eq.  alloxan  to  the  2 eq.  of  sulphurous  acid,  which  is  thus  converted 
into  sulphuric  acid,  while  the  elements  of  cyanoxalic  acid,  ammonia, 
and  water  combine  to  uramil. 

1892.  Thionuric  acid  forms  with  the  alkalies  very  soluble  salts  ; Thionuric 
with  the  alkaline,  earths  either  insoluble  or  sparingly  soluble  salts,  ^etallicox- 
which  are  however  readily  dissolved  by  dilute  acids;  they  generally  ides. 

are  formed  of  1 eq.  of  acid  and  2 eq.  of  the  metallic  oxide.  All  these 
salts  evolve  sulphurous  acid  abundantly  when  treated  with  concen- 
trated sulphuric  acid ; when  fused  with  hydrate  of  potassa,  sulphite 
of  potassa  is  formed. 

1893.  Uramil.  C8N3H506 ; eq.=  144.41.  Discovered  by  Wohler  Uramil. 
and  Liebig.  A product  of  the  decomposition  of  thionuric  acid. 

A cold  saturated  solution  of  thionurate  of  ammonia  is  made  boiling  hot,  and 
then  treated  with  hydrochloric  acid  till  it  has  a strongly  acid  reaction,  when  it  is 
again  heated  till  a slight  turbidity  is  observed,  and  allowed  to  cool  slowly  ; or  a 
boiling  saturated  solution  of  the  same  salt  may  be  mixed  with  hydrochloric  or 
dilute  sulphuric  acid,  and  then  kept  boiling  until  the  whole  is  converted  to  a 
semifluid  mass.  It  is  obtained  in  a plume-form  aggregation  of  fine  but  hard 
needles,  or  as  a fine  porous  powder,  consisting  of  fine  needles  which  have  a 
silky  lustre,  and  are  permanent  in  the  air,  but  acquire  a pink  tint  when  heated. 

1894.  It  is  insoluble  in  cold,  but  taken  up  in  small  quantity  by  Properties, 
boiling  water  ; soluble  in  ammonia  and  the  caustic  alkalies  in  the 

cold,  from  which  it  is  precipitated  by  acids  unchanged.  The  solu- 
tion of  uramil  in  ammonia  and  caustic  potassa  acquires  a purple  co- 
lour by  exposure  to  the  air,  and  deposits  green  acicular  crystals,  of  a 
brilliant  metallic  lustre;  if  boiled  in  the  caustic  potassa,  it  is  decom- 
posed into  uramilic  acid  with  the  evolution  of  ammonia.  It  is  solu- 
ble in  concentrated  sulphuric  acid,  from  which  it  is  again  precipi* 


430 


Chap.  VI. 


Action  of 
nitric  acid. 


Uramilic 

acid. 

Prepara- 

tion. 


Properties. 


Salts  of 
uramilic 
acid. 


Alloxantin. 


Prepara- 

tion. 


Properties. 


Cyanogen  and  its  Compounds. 

tated  by  water ; by  boiling  in  dilute  acids  it  suffers  the  same  change 
as  in  caustic  potassa.  By  boiling  with  the  oxides  of  silver  and  mer- 
cury it  is  converted  into  murexid,  and  the  oxide  is  reduced. 

1895.  With  concentrated  nitric  acid  it  is  resolved  into  alloxan, 
with  the  evolution  of  hyponitrous  acid,  and  the  formation  of  nitrate 
of  ammonia.  The  above  decomposition  of  the  thionurate  of  ammo- 
nia consists  in  the  separation  of  the  elements  of  2 eq.  of  sulphate  of 
ammonia.  Uramil  may  be  considered  as  uric  acid,  in  which  the 
urea  is  replaced  by  1 eq.  ammonia  and  2 eq.  water. 

1896.  Uramilic  Acid.  C^NsH^O^.  Discovered  by  Wohler  and 
Liebig.  A product  of  the  decomposition  of  uramil. 

A saturated  solution  of  thionurate  of  amraonia  in  cold  water  is  added  to  a small 
quantity  of  sulphuric  acid,  and  the  mixture  evaporated  in  a water-bath,  when  the 
uramilic  acid  is  slowly  deposited  in  transparent  prisms  of  a glassy  lustre.  If  a 
white  amorphous  deposit,  which  is  soluble  in  hot  water,  be  at  the  same  time  ob- 
tained, it  arises  from  the  presence  of  undecomposed  acid  thionurate  of  ammonia; 
this  is  again  dissolved  in  water  mixed  with  sulphuric  acid,  and  treated  as  before. 

1897.  Colourless  four-sided  prisms,  or  fine  silky  needles  ; is  so- 
luble in  6 — 8 parts  of  cold,  and  in  3 parts  of  boiling  water  ; loses  no 
weight  when  heated  to  212°,  but  acquires  a slightly  pink  colour; 
the  solution  has  a feeble  acid  reaction.  It  is  soluble  in  concentrated 
sulphuric  acid  with  effervescence,  but  without  colouring  the  acid. 
By  boiling  in  strong  nitric  acid,  a yellow  solution  is  obtained,  which 
yields  on  evaporation  white  crystalline  and  sparingly  soluble  scales 
or  granular  crystals;  they  are  dissolved  by  alkalies,  and  again  pre- 
cipitated by  acetic  acid.  In  its  formation  2 eq.  of  uramil  lose  the 
elements  of  1 eq.  of  ammonia,  which  are  replaced  by  3 eq.  of  water. 

1898.  The  uramilic  acid  forms  with  ammonia  and  the  fixed  alka- 
lies soluble  crystallizable  salts  ; lime  and  baryta  are  not  thrown  down 
from  their  saline  solution  by  the  free  acid  ; but  on  the  addition  of 
ammonia  a white  precipitate  is  formed,  which  again  disappears  in  a 
large  quantity  of  water.  Uramilate  of  ammonia  produces  with  ni- 
trate of  silver  a dense  white  precipitate,  which  contains  from  63 — 64 
per  cent,  of  silver. 

1899.  Allorantin.  C.(N2H50,o ; eq. =162.26.  First  observed  by 
Prout  as  a product  of  the  decomposition  of  uric  acid  by  nitric  acid ; 
it  is  also  formed  by  the  action  of  chlorine  on  uric  acid,  as  likewise 
from  alloxan  by  the  action  of  deoxidizing  agents. 

1900.  From  uric  acid . one  part  of  uric  acid  is  added  to  32  parts  of  water, 
which  is  brought  to  the  boiling  point,  and  then  treated  with  dilute  nitric  acid  in 
successive  portions  till  a perfect  solution  is  obtained  ; it  should  then  be  evapo- 
rated to  two  thirds  of  its  volume,  when,  after  standing  for  some  hours,  or  a day, 
crystals  of  alloxantin  will  be  deposited,  w’hich  should  be  purified  by  recryetal- 
lization. 

From  aUoxan : it  is  obtained  in  large  quantity  by  transmitting  a stream  of 
hydrosulphuric  acid  gas  through  a solution  of  alloxan,  when  first  sulphur,  and 
then  a crystalline  mass  of  alloxantin  is  deposited ; it  is  separated  from  the  sul- 
phur by  solution  in  hot  water,  which  yields  by  evaporation  and  cooling  pure 
crystals  of  alloxantin.  It  may  also  be  formed  by  adding  zinc  and  hydro- 
chloric acid  to  a solution  of  alloxan,  but  here  an  excess  of  acid  must  be  care- 
fully avoided  ; or  by  boiling  alloxan  in  moderately  strong  sulphuric  acid,  when 
it  is  deposited  as  the  solution  cools.  If  a solution  of  alloxan  be  exposed  to 
the  action  of  a galvanic  battery,  oxygen  is  evolved  at  the  positive  electrode, 
while  the  negative  is  covered  with  a crystalline  crust  of  alloxantin. 

1901.  Short  oblique  four-sided  prisms  of  the  oblique  prismatic 
system,  the  obtuse  angle  of  the  prism  being  105°.  The  crystals  are 


Murexid, 


431 


colourless,  or  have  a slightly  yellow  tint ; in  an  ammoniacal  atmos-  sect,  iv. 
phere  they  become  red,  acquire  a greenish  metallic  lustre,  and  are 
readily  reduced  to  powder  ; exposed  to  212°  they  undergo  no  change 
of  weight,  but  at  300°  lose  15.4  per  cent.^S  eq.  water ; sparingly 
soluble  in  cold,  more  freely  in  boiling  water.  The  solution  reddens 
litmus  ; is  converted  into  alloxan  by  being  warmed  with  nitric  acid, 
or  by  a solution  of  chlorine  ; forms  with  the  salts  of  silver  a black 
precipitate  of  metallic  silver  ; it  is  decomposed  by  alkalies  ; barytic 
water  causes  a violet-blue  precipitate,  which  is  first  rendered  colour- 
less by  heat  and  then  disappears  ; by  adding  an  excess  of  baryta  to 
this  solution  a brilliant  white  precipitate  is  formed. 

1902.  If  a solution  of  alloxan,  instead  of  being  left  in  contact  with 
zinc  and  hydrochloric  acid  at  common  temperature,  be  heated  to  the 
boiling  point,  and  kept  at  that  temperature  for  some  time,  it  deposits, 
on  cooling,  yellow  granular  crystals  of  a brilliant  lustre  and  sparing 
solubility  in  boiling  water,  and  of  characters  essentially  different 
from  alloxantin. 

1903.  If  a stream  of  hydrosulphuric  acid  gas  be  passed  through  a Products  of 
boiling  solution  of  alloxantin,  a further  precipitation  of  sulphur  en- 

sues,  and  the  solution  acquires  a strongly  acid  reaction  ; if  neutralized  afloxantin. 
by  carbonate  of  ammonia,  it  deposits  on  cooling  an  abundant  crop  of 
white  silky  acicular  crystals  of  an  ammoniacal  salt,  which,  when 
heated  to  212°  in  the  air,  becomes  of  a blood-red  colour;  its  compo- 
sition is  represented  by  the  formula  C8N3H208,  and  it  may  therefore 
be  considered  to  be  a compound  of  cyanoxalic  acid  with  1 eq.  ammo- 
nia and  4 eq.  water.  The  acid  in  this  salt  appears  in  the  moment  of 
its  separation  from  the  ammonia  with  which  it  was  combined  to  be 
decomposed  into  a variety  of  new  products.  It  is  proposed  to  call 
this  acid  the  dialuric  acid,  since  its  properties  appear  to  differ  from 
those  of  the  cyanoxalic, 

1904.  If  a hot  saturated  solution  of  alloxantin  be  treated  with  a so-  Action  of 
lution  of  sal  ammoniac,  it  instantly  acquires  a purple-red  colour,  ammonia, 
which  disappears  after  a few  moments,  while  the  solution  becomes 
turbid,  and  deposits  brilliant  white  scales  of  uramil,  but  they  are 

pink  when  dried  ; the  same  occurs  with  the  acetate,  the  oxalate,  and 
other  ammoniacal  salts ; the  solution  contains,  after  the  decomposi- 
tion, alloxan  and  free  hydrochloric  acid. 

1905.  Two  eq.  alloxantin  and  1 eq.  ammonia  contain  the  elements  of  1 eq.  mL 
uramil,  1 eq.  alloxan,  and  4 eq.  water.  By  heating  a solution  of  alloxantin  in 
pure  ammonia,  the  products  first  formed  are  uramil  and  mykomelinate  of  ammo- 
nia, both  of  which  suffer  further  changes  by  the  continued  action  of  ammonia 
and  the  atmospheric  air.  If  a solution  of  alloxantin  in  ammonia,  which  has 
been  prepared  in  the  cold,  be  spontaneously  evaporated  by  exposure  to  the  air, 
oxygen  is  absorbed,  and  crystals  of  the  oxalurate  of  ammonia  are  obtained  : 3 eq. 
alloxantin,  7 eq.  oxygen,  and  6 eq.  ammonia,  contain  the  elements  of  4 eq.  oxa- 
lurate of  ammonia  and  5 eq.  water. 

1906.  If  oxide  of  silver  be  heated  in  a solution  of  alloxantin,  a por-  Action  0f 
tion  of  the  former  is  reduced  with  effervescence,  and  the  solution  oxide  of 
contains  pure  oxalurate  of  silver.  In  this  reaction  3 eq.  oxygen  silver, 
from  the  oxide  of  silver  decompose  l eq.  alloxantin  into  1 eq.  water, 

2 eq.  carbonic  acid,  and  1 eq.  oxaluric  acid,  which  last  unites  with 
some  undecomposed  oxide  of  silver. 

1907.  Murexid.  C12N5H608;  eq.=  197.19.  The  purpurate  of  Murexid. 
ammonia  discovered  by  Prout. 


432 


Chap.  VI. 
Processes. 


Theory. 


Properties. 


Cyanogen  and  its  Compounds. 

By  heating  a mixture  of  equal  parts  of  peroxide  of  mercury  and  uramilic  acid 
in  3ti — 40  parts  of  water,  with  the  addition  of  an  exceedingly  small  quantity  of 
ammonia  ; as  soon  as  the  liquid  has  acquired  a deep  purple  colour,  it  is  filtered 
and  allowed  to  rest,  when  the  murexid  crystallizes ; or  by  dissolving  uramil  by 
the  aid  of  heat  in  ammonia,  and  when  the  solution  has  cooled  to  lfi0°,  alloxan  is 
added  until  a very  slight  alkaline  reaction  is  observed. 

Or  a solution  of  uric  acid  in  dilute  nitric  acid  is  evaporated  until  it  acquires  a 
flesh-red  colour,  when  it  is  allowed  to  cool  to  100°,  and  is  then  treated  with  a 
dilute  aqueous  solution  of  ammonia,  till  the  presence  of  free  ammonia  is  re* 
marked  by  the  odour  ; the  solution  is  then  diluted  with  half  its  volume  of  boiling 
water,  and  allowed  to  cool.* 

Or  a boiling  saturated  solution  of  alloxantin  in  water  is  treated  with  ammonia 
in  excess  till  the  precipitated  uramil  is  redissolved,  when  a solution  of  alloxan  is 
added,  so  that  only  a slight  alkaline  reaction  is  left,  and  the  whole  is  allowed  to 

cool. 

Or  by  heating  alloxantin  with  sal  ammoniac  or  oxalate  of  ammonia,  and  after 
the  formation  of  uramil  adding  ammonia  till  the  former  is  redissolved,  and  then 
alloxan.  Murexid  may  be  formed  by  a number  of  other  processes,  by  bringing 
together  many  of  the  products  of  uric  acid  with  ammonia,  with  or  without  the 
presence  of  atmospheric  air. 

1908.  When  the  oxygen  from  ]£  eq.  of  peroxide  of  mercury  is 
added  to  2 eq.  uramil,  they  may  give  rise  to  the  formation  of  1 eq. 
murexid,  1 eq.  alloxanic  acid,  and  3 eq.  water.  Alloxan  appears  to 
have  the  same  action  upon  a solution  of  uramil  in  ammonia  as  the 
peroxide  of  mercury.  One  eq.  alloxan,  2 eq.  alloxantin,  and  4 eq. 
ammonia,  contain  the  elements  of  2 eq.  murexid  and  14  eq.  water. 
The  solution  of  uric  acid  in  dilute  nitric  acid  contains  principally 
alloxantin,  urea,  and  nitrate  of  ammonia  : evaporated  until  the  flesh- 
red  colour  appears,  a portion  of  the  alloxantin  is  converted  by  the  action 
of  free  nitric  acid  into  alloxan,  a portion  of  which,  by  a further  action, 
gives  rise  toparabauic  acid.  But  when  alloxan  and  alloxantinare  simul- 
taneously present  in  a solution,  an  excess  of  ammonia  produces  a deep 
purple-red  liquid  from  which  murexid  is  deposited.  If  the  solution 
contain  an  excess  of  alloxantin,  the  crystals  of  murexid  are  mixed 
with  uramil ; with  an  excess  of  alloxan,  mykomelinate  of  ammonia 
is  formed,  which  also  falls  with  the  murexid.  The  parabanic  acid 
present  passes,  when  the  solution  of  uric  acid  is  saturated  with  am- 
monia, into  oxaluric,  which  is  obtained  in  crystals  of  oxalurate  of 
ammonia  by  evaporating  the  mother-liquor. 

1909.  Murexid  crystallizes  in  short  four-sided  prisms,  two  faces 
of  which,  like  the  upper  wings  of  the  cantharides,  reflect  a green 
metallic  lustre.  The  crystals  are  transparent,  and  by  transmitted 
light  are  of  a garnet-red  colour.  It  forms  a brownish-red  powder, 
which,  under  the  polishing  steel,  acquires  a brilliant  metallic  green 
colour.  It  is  insoluble  in  ether  and  alcohol;  sparingly  soluble  in 
cold,  but  more  readily  in  boiling  water,  on  the  cooling  of  which  it 
crystallizes  unchanged  ; insoluble  in  a saturated  solution  of  carbo- 
nate of  ammonia,  soluble  in  caustic  potassa  with  a beautiful  indigo- 
blue  colour,  which  disappears  on  the  application  of  heat  with  the 
evolution  of  ammonia. 


* In  applying  this  method  of  preparation,  it  is  advisable  to  test  a small  quantity  of 
the  solution  of  uric  acid  from  time  to  lime  by  saturating  it  with  ammonia  ; if  it  be 
rendered  turbid  by  the  ammonia,  and  a red  powder  falls,  a small  quantity  of  nitric 
acid  must  be  added  to  the  hot  solution  of  the  uric  acid  ; but  if  a yellow  slimy  precipi- 
tate be  formed,  the  solution  will  only  give  rise  to  the  formation  of  murexid  after  a 
stream  of  hydrosulphuric  acid  gas  has  been  transmitted  through  it. 


433 


Cystic  Oxide. 


1910.  It  is  decomposed  either  in  the  solid  state  or  in  solution  by  Sect,  iv. 
all  the  mineral  acids,  with  the  separation  of  brilliant  scales  of  mu-  Decom- 
rexan  ; the  liquid  contains  ammonia,  alloxantin,  alloxan,  and  urea,  posed. 
The  instant  the  murexid  is  brought  into  contact  with  hydrosulphu- 

ric  acid  it  is  decomposed  into  alloxantin,  dialuric  acid,  and  murexan, 
with  the  separation  of  sulphur.  An  equivalent  of  alloxan,  alloxan- 
tin, murexan,  and  urea,  together  with  2 eq.  ammonia,  contain  the 
elements  of  2 eq.  murexid  and  11  eq.  water. 

1911.  Murexan.  C6N2H405 ; eq.=109.02.  The  purpuric  acid  Murexan. 
discovered  by  Prout  as  the  product  of  the  decomposition  of  murexid. 
Prepared  by  dissolving  murexid  in  caustic  potassa  by  the  aid  of  heat, 
which  is  applied  till  the  blue  colour  disappears,  when  dilute  sulphu- 
ric acid  is  added  in  excess. 

1912.  It  falls  in  crystalline  scales  of  a silky  lustre  ; is  insoluble 
in  water  and  dilute  acids,  but  is  taken  up  by  ammonia  and  the  fixed 
alkalies  in  the  cold  without  neutralizing  them.  It  is  dissolved  by 
concentrated  sulphuric  acid,  from  which  it  is  again  precipitated  un- 
changed by  water.  If  a solution  of  murexan  in  ammonia  he  exposed 
to  the  air,  it  acquires  a purple-red  colour,  and  deposits  the  brilliant 
crystals  of  murexid ; with  an  excess  of  ammonia  the  solution  again 
becomes  colourless,  and  is  then  found  to  contain  oxalurate  of  ammo- 


Uric  Oxide, 
or  Xanthic 
oxide. 


1913.  Two  eq.  murexan,  1 eq.  ammonia,  and  3 eq.  oxygen,  con- Theory, 
tain  the  elements  of  1 eq.  murexid  and  3 eq.  water  ; 1 eq.  murexan, 

3 eq.  oxygen,  and  1 eq.  ammonia,  are  the  constituents  of  1 eq.  oxa- 
lurate of  ammonia. 

1914.  Uric  Oxide,  or  Xanthic  Oxide.  C5N2H202.  A rare  consti- 
tuent of  urinary  calculi  ; first  discovered  by  Marcet. 

1915.  Urinary  calculi,  which  contain  this  ingredient,  are  dissolved 
in  caustic  potassa  and  the  solution  saturated  with  carbonic  acid, 
when  the  uric  oxide  is  precipitated. 

1916.  A white  precipitate  ; when  dried,  it  forms  a pale  yellow  Properties 
hard  mass,  which  acquires  a waxy  lustre  by  friction : it  is  dissolved 

by  the  pure  and  carbonated  alkalies  ; in  small  quantity  by  hot  water, 
hydrochloric  and  oxalic  acids.  It  is  soluble  in  concentrated  sulphu- 
ric acid  with  a yellow  colour ; no  precipitation  is  caused  by  the  ad- 
dition of  water  to  the  solution.  It  is  dissolved  in  nitric  acid  without 
effervescence  ; on  evaporating  to  dryness,  a lemon-yellow  residue  is 
left,  which  is  not  reddened  by  ammonia,  is  partially  soluble  in  water, 
but  perfectly  and  easily  in  potassa ; the  solution  has  a light  reddish- 
yellow  colour,  and  leaves  on  evaporation  a red  residue. 

1917.  Exposed  to  the  destructive  distillation,  it  evolves  an  odour 
of  urine,  hydrocyanic  acid,  and  carbonate  of  ammonia,  but  no  urea. 

The  calculi,  which  contain  uric  oxide,  have  a light  brown,  or  bright 
brown  surface  ; the  fracture  is  scaly,  of  a strong  lustre,  and  also  of  a 
brown  or  deep  flesh  colour ; by  friction  the  lustre  becomes  resinous. 

1918.  Cystic  Oxide.  Discovered  by  Wollaston  ; a rare  consti- 
tuent of  urinary  calculi ; an  organic  base. 

1919.  The  calculus  is  dissolved  in  aqueous  ammonia,  and  the 
filtered  solution  evaporated  in  the  air,  when  the  cystic  oxide  crystal- 
lizes. 

1920.  In  the  calculus  it  exists  as  a yellowish-white  confused  crys- 

55 


Destructive 

distillation. 


Cystic  Ox- 
ide. 


434 


Vegetable  Alkalies. 


chap-  vn.  talline  mass  of  a brilliant  lustre : crystallizes  from  its  solution  in 
potassa,  on  the  addition  of  acetic  acid,  in  hexagonal  plates  ; from 
ammonia,  in  white  transparent  scales.  It  is  decomposed  by  heat, 
with  the  evolution  of  sulphurous  and  ammoniacal  products  of  an  of- 
fensive odour.  It  is  readily  dissolved  by  mineral  acids,  with  which 
it  forms  crystalline  compounds. 

Salt  of.  1921.  It  forms  with  hydrochloric  acid  an  anhydrous  salt  which  is 

composed  of  1 eq.  of  the  base  and  acid.  The  salt  with  nitric  acid  i3 
formed  of  1 eq.  of  acid,  1 eq.  of  base,  and  2 eq.  water,  the  half  of 
which  is  separated  by  a temperature  of  105°.  It  is  soluble  in  the 
pure  and  carbonated  alkalies  ; but  if  the  solution  be  heated  it  is  de- 
composed at  first  with  the  evolution  of  ammonia,  but  as  the  evapora- 
tion proceeds,  a very  combustible  gas,  which  burns  with  a blue  flame, 
and  smells  like  sulphuret  of  carbon,  is  given  off.  The  occurrence  of 
the  cystic  oxide  is  so  rare,  that  it  is  impossible  to  institute  any  inves- 
tigation of  this  remarkable  substance. 

According  to  the  analysis  of  Thaulow,  its  formula  is  C6NH604S2. 
L.  823. 


CHAPTER  VII. 

Section  I.  Vegetable  Alkalies  * 

Vegetable  1922.  These  alkaline  bodies  have  been  discovered  since  the  year 
alkalies.  1817,  and  their  number  is  daily  increasing.  The  most  important 
only  can  be  comprised  in  this  chapter.  Almost  all  plants,  which  are 
remarkable  for  their  poisonous  or  medicinal  properties,  when  sub- 
jected to  a chemical  examination,  have  been  found  to  contain  an 
alkaline  principle. 

Precipita-  1923.  It  has  been  found  that  all  the  vegetable  alkalies  are  preci- 
ted by  tan-  pitted  by  tanniu,  or  infusion  of  nutgalls.  These  precipitates  are 
usually  white  powders,  bitannates  of  the  alkali,  insoluble  in  cold 
water,  and  easily  decomposed  by  an  alkaline  or  earthy  base.  Henry 
has  proposed  infusion  of  nutgalls  as  an  excellent  reagent  for  obtain- 
ing these  alkalies.  His  process  is  as  follows  : 

Digest  the  plant  containing  the  alkali  in  warm  water,  acidulated  with  sulphu- 
ric acid.  Neutralize  the  clear  liquor  bv  potassa,  and  add  a concentrated  infusion 
of  nutgalls  as  long  as  a precipitate  falls.  Separate  the  precipitate,  wash  it  with 
cold  water,  and  mix  intimately  with  a slight  excess  of  slaked  lime.  Dry  the 
mixture  over  the  vapour-bath  till  it  is  reduced  to  powder.  Digest  this  powder  in 
alcohol  or  ether.  Filter,  distil  off  the  alcohol  or  ether.  Set  the  residue  aside  for 
some  days.  The  alkali  will  be  deposited  in  crystals. t 

How  dis-  1924.  These  bodies  have  been  distinguished  by  names  terminating 
tinguished.  jn  ^ that  they  might  resemble  potassa,  soda,  and  ammonia,  and  the 
name  of  the  neutral  principles  with  which  they  are  associated  in 
vegetables  has  been  made  to  terminate  in  ine  or  in.  They  are  all 
compounds  of  carbon,  hydrogen,  nitrogen,  and  oxygen. 


* The  materials  for  this  chapter  have  been  principally  derived  from  Thomson’s 
Chem  of  Org.  Bodies,  to  which  the  student  must  be  referred  for  the  description  of 
many  ot  the  less  important  substances, 
t Jour,  de  Pharm.  xxi.  213. 


Quinia. 


435 


1925.  Cinchonia.  C2oH12NOl£*,  — 158.0,  was  detected  by  Pel  Sect,  i. 
letier  and  Caventou  in  1820,  in  the  gray  Peruvian  bark,  which  is  cinchonia. 
considered  as  the  bark  of  the  cinchona  nitida  or  the  cinchona  conda - 

minea , and  is  not  much  esteemed  for  its  medical  properties.  But 
there  is  reason  to  suspect  that  the  cinchona  lancifolia  of  Loxa,  the 
most  celebrated  of  all  the  varieties  contains  the  same  principle. 

It  i _ obtained  from  the  pale  bark  by  digesting  it  in  dilute  hydro- 
chloric acid,  precipitation  by  an  alkali  or  earth,  solution  in  alcohol 
and  crystallization.! 

1926.  It  crystallizes  in  prismatic  needles,  and  requires  2500  times  CrystaUme 
its  weight  of  water  for  solution.  It  is  very  soluble  in  alcohol ; has  s?q™bflity. 
a bitter  taste,  is  not  altered  by  exposure  to  the  air.  Its  alkaline  pro- 
perties are  well  marked. 

1927.  The  salts  of  cinchonia  have  a bitter  taste ; are  precipitated  Characters 
by  oxalates,  tartrates  and  gallates,  and  by  the  infusion  of  gallnuts.  of  its  salts‘ 
It  combines  with  acids  forming  neutral  salts  and  disalts,  or  salts  com- 
posed of  two  atoms  base  united  to  1 atom  acid.  T. 

1928.  Quinia.  C20Hi2NO2==  162.0.  In,  1820  Pelletier  and  Caven-  Quinia. 
tou  pointed  out  the  alkaline  character  of  this  substance,  and  showed 

it  might  be  obtained  in  a separate  state. | Since  that  period  sul- 

phate of  quinia  has  come  into  general  use  as  a medicine,  and  has 
almost  superseded  the  use  of  bark. 

1929.  Quinia  may  be  extracted  from  the  yellow  bark  usually 
considered  as  the  cinchona  cordifolia. 

The  bark  is  boiled  in  water  acidulated  with  sulphuric  acid:  the  solution  of  Process, 
sulphate  of  quinia  thus  formed  is  decomposed  by  lime  ; sulphate  of  lime  is 
formed,  and  the  quinia  mixes  mechanically  with  it,  as  it  is  precipitated.  Alcohol 
dissolves  the  quinia  and  leaves  the  sulphate  of  lime.  The  alcohol  being  evapo- 
rated, the  quinia  is  procured  by  itself;  neutralized  by  dilute  sulphuric  acid,  and 
boiled  with  animal  charcoal  to  destroy  the  colouring  matter,  a solution  is  pro- 
cured, which  gives  crystals  of  the  sulphate  on  evaporation. 

1930.  As  sulphate  of  quinia  is  prepared  on  a large  scale,  it  is 

more  convenient  to  obtain  quinia  from  that  salt.  Nothing  more  is  suiphate. 
necessary  than  to  dissolve  the  sulphate  in  water,  and  to  mix  the  so- 
lution with  a dilute  solution  of  ammonia.  The  quinia  falls  in  white 
flocks,  which  become  a little  coloured  during  drying. 

1931.  It  crystallizes  with  difficulty  from  hot  alcohol  in  fine  nee- Characters, 
dies  and  then  is  in  the  state  of  a hydrate.  Exposed  to  heat,  it 
softens  and  falls  down  as  a white  powder ; at  302°,  or  a few  degrees 
higher,  it  melts  and  loses  the  whole  of  its  water  (T  ).  Suddenly 
cooled,- it  becomes  yellow  and  brittle  ; slowly  cooled,  it  assumes  a 

fibrous  texture,  and  becomes  opaque.  By  friction  it  becomes  nega- 
tively electric. 


* The  atomic  composition  is  given,  as  stated  by  Thomson. 

t The  following  process  was  adopted  by  Pelletier  and  Caventou  for  the  extraction  of  Pelletier  and 
cinchonia.  Two  kilogrammes  (4  2-5  lbs.  avoirdupois)  of  gray  bark  in  powder  were  di-  Caventou*# 
gested  in  6 kil.  (13  1-5  lbs.)  of  alcohol.  This  treatment  was  repeated  four  times.  The  proCess' 
alcoholic  tinctures  were  all  united,  and  the  alcohol  was  distilled  off  after  the  addition 
of  two  litres  (122  cubic  inches)  of  water.  The  residual  liquor  was  filtered,  and  it  left 
on  the  filter  a reddish  matter  apparently  resinous,  which  was  washed  with  water  con- 
taining a little  potassa  till  the  liquid  passed  without  colour.  The  matter  remaining 
on  the  filter,  after  being  well  washed  with  distilled  water  is  greenish  white,  very  fu- 
sible, soluble  in  alcohol,  and  capable  of  crystallizing.  It  was  cinchonia  with  foreign 
matter.  It  was  purified  by  the  action  of  hydrochloric  acid,  magnesia,  and  repeated 
boiling  in  alcohol  which  dissolved  the  cinchonia. 

$ Ann.  de  Chim.  et  Phys.  xv.  345. 


436 


Vegetable  Jllkalies. 


Chap,  vii.  1932.  When  freed  from  water  and  placed  in  that  liquid,  quinia 
swells  and  absorbs  it.  Its  taste  is  intensely  bitter.  It  is  soluble  in 
200  times  its  weight  of  boiling  water ; very  soluble  in  alcohol  and 
in  ether. 

distirf tS  1933.  The  salts  of  quinia  are  distinguished  by  a strong  bitter  taste ; 
guished.  those  in  crystals  have  a pearly  lustre  ; most  of  them  are  soluble  in 

water,  and  several  in  alcohol  and  in  ether.  These  solutions  are  pre- 
cipitated by  oxalic,  tartaric,  and  gallic  acids,  and  also  by  infusion  of 
nutgalls. 


Sulphate  of  1934.  Sulphate  of  Quinia.  The  powerfully  febrifuge  properties 
quinia.  0f  this  salt  have  introduced  it  into  general  use  as  a medicine,  and  it 
has  become  an  important  article  of  manufacture,  especially  in 
France.* * * §  The  process  usually  followed  is  the  following  of  M. 
Henri,  junior,  with  some  slight  modifications-! 

Adultera-  1935.  Sulphate  of  quinia,  from  its  commercial  value,  is  frequently 
non  detect-  adulterated.  The  substances  commonly  employed  for  the  purpose 
are  water,  sugar,  gum,  starch,  ammoniacal  salts,  and  earthy  salts, 
such  as  sulphate  of  lime  and  magnesia,  or  acetate  of  lime.  Pure 
sulphate  of  quinia,  when  deprived  of  its  water  of  crystallization  by  a 
heat  of  212°,  should  lose  only  from  8 to  10  per  cent,  of  water.  Su- 
gar may  be  detected  by  dissolving  the  suspected  salt  in  water,  and 
adding  precisely  so  much  carbonate  of  potassa  as  will  precipitate  the 
quinia.  The  taste  of  the  sugar,  no  longer  obscured  by  the  intense 
bitter  of  the  quinia,  will  generally  be  perceived  ; and  it  may  be  se- 
parated from  the  sulphate  of  potassa,  by  evaporating  gently  to  dry- 
ness, and  dissolving  the  sugar  by  boiling  alcohol.  Gum  and  starch 
are  left  when  the  impure  sulphate  of  quinia  is  digested  in  strong 
alcohol.  Ammoniacal  salts  are  discovered  by  the  strong  odour  of 
ammonia,  which  may  be  observed  when  the  sulphate  is  put  into  a 
warm  solution  of  potassa.  Earthy  salts  may  be  detected  by  burning 
a portion  of  the  sulphate.! 

Disulphate.  1936.  Disulphate  of  Quinia  effloresces;  is  soluble  in  740  times 
its  weight  of  water  at  55°,  and  in  30  times  its  weight  of  boiling 
water.  It  dissolves  in  80  times  its  weight  of  alcohol  of  sp.  gr.  0.85. 
It  crystallizes  in  tufts  composed  of  fine  needles  of  a pearly  lustre.  It 
fuses  and  then  resembles  liquid  wax:  at  a higher  temperature  it  as- 
sumes a fine  red  colour,  and  burns  without  leaving  any  residue. 

From  Liebig’s  analysis,  as  quoted  by  Thomson,  it  is  composed 
of  85  quinia,  10  sulphuric  acid,  and  4.17  water. 

1937.  Neutral  sulphate  of  quinia  may  be  formed  by  adding  a 
little  sulphuric  acid  to  the  solution  of  the  disulphate. § 

1 938.  Salicin , CjHsC^^AS.O,  although  notalkaline  is  analogous  to 


Composi- 

tion. 

Neutral 

sulphate. 


* The  annual  produce  in  Paris  exceeds  1200,00  ounces  per  annum.  T. 

+ For  details  of  which,  see  T.  Orff.  Bodies,  233,  and  Ure’s  Diet.  Arts  and  Manuf. 
1064. 

t Several  of  the  preceding  directions  are  taken  from  a paper  on  the  subject  by  Phil- 
lips. Phil.  Mag.  and  Ann.  ni.  111.  (Turner.)  According  to  Thomson,  margaric  acid 
and  boracic  acid  are  employed  ; the  former  may  be  separated  by  weak  hydrochloric 
acid  which  dissolves  sulphate  of  quinia  but  leaves  the  margaric  acid  3 the  boracic  acid 
is  discovered  by  incinerating  a portion  of  the  suspected  salt. 

§ Hydro ferrocyanate  of  Quinia  has  been  found  a more  powerful  febrifuge  than  the 
sulphate,  but  is  liable  to  decomposition.  For  the  method  of  preparing  this,  and  the 
other  salts  of  quinia,  see  T.  Orff.  Bodies , 236. 


Narcotina . 


437 


the  alkalies  from  cinchona.  It  is  obtained  from  the  bark  of  the  willow  sect,  i. 
{salix  helix),  and  exists  in  several  species,  also  in  the  bark  of  the  Salicin, 
poplar  ( populus  tremula).  It  is  white,  very  bitter,  soluble  in  water 
and  alcohol.  With  concentrated  sulphuric  acid  it  becomes  of  a 
beautiful  red  colour ; this  holds  with  solutions  containing  only 
of  their  weight  of  it ; and  the  presence  of  salicin  in  any  bark  may 
thus  be  ascertained.  It  has  been  employed  as  a substitute  for Use' 
quinia. 

1939.  Veratria , C34H22NQ6,=288,  the  alkaline  principleof  veratrum  Veratria. 
album , white  hellebore,  and  colchicum  autumnale , meadow  saffron, 

has  the  aspect  of  resin,  is  white  and  fusible  at  about  240°.  Alco- 
hol and  ether  dissolve  it.  It  has  no  smell,  but  when  drawn  into  the  Characters, 
nostrils,  even  in  minute  quantity,  it  produces  violent  and  long-con- 
tinued sneezing.  Its  taste  is  excessively  acrid,  it  occasions  frightful 
vomiting,  and  a few  grains  are  fatal. ^ 

1940.  Strychnia  exists  in  the  seeds  or  fruits  of  several  species  of  strychnia. 
strychnos , particularly  in  the  nux  vomica.  It  was  found  also  in  the 
poisonous  matter  called  upas.  It  is  intensely  bitter,  and  requires  ri 
2500  times  its  weight  of  boiling,  and  6667  times  its  weight  of  cold  13raC  erS' 
water  for  solution.  It  is  highly  poisonous  ; occasioning  violent  con- 
tractions of  the  muscles,  and  tetanus  ; the  best  antidote  is  infusion  of 
nutgalls,  or  warm  tea.  In  very  small  doses  it  has  been  employed  in 
paralysis,  and  it  is  said  sometimes  with  success. 

1941.  Brucia  resembles  the  foregoing,  and  has  been  found  to  ac- 
company it  in  the  different  vegetable  bodies  which  contain  it.f 

1942.  Narcotina.  C40H2,jNO12,  = 370.24.  Discovered  by  Desrone  Narcotina. 
in  1803. t It  is  obtained  from  opium. 

Digest  opium  in  water,  filter  and  evaporate  to  the  consistence  of  an  extract.  Process. 
Ether  digested  on  this  extract  dissolves  the  narcotina  together  with  some  other 
substances.  Distil  off  the  ether,  and  dissolve  the  residual  matter  in  hot  water 
or  boiling  alcohol,  digest  the  solution  with  animal  charcoal.  Decant  the  clear 
liquid  and  precipitate  the  narcotina  by  ammonia.  If  not  white,  the  narcotina 
may  be  dissolved  in  hydrochloric  acid,  and  the  solution  be  again  treated  with 
animal  charcoal,  thrown  down  by  ammonia,  washed  and  dried. 

1943.  Narcotina  is  white,  and  is  deposited  from  boiling  ether  or  Characters* 
alcohol  in  needle-form  crystals  of  a pearly  lustre.  It  does  not  re- 
store the  blue  colour  of  litmus  paper  reddened  by  acids  ; but  as  it 
combines  with  and  neutralizes  acids  must  be  considered  as  an  alkali.  ^cljonof- 

1944.  Its  taste  is  not  bitter.  In  contact  with  hyponitrous  acid  it  hyponi- 
assumes  a carmine-red  colour  and  gives  out  red  vapours.  In  about  trous  acid, 
half  a minute  the  action  increases,  the  narcotina  catches  fire  and  burns 

with  a large  white  flame.  There  remains  a blackish  spongy  matter 
consisting  partly  of  charcoal  and  partly  of  bitter  principle  of  Welter, 
or  carbazotic  acid.§  ’ It  is  insoluble  in  cold  water,  very  little  soluble 
in  boiling  water,  but  readily  soluble  in  ether  and  in  fixed  oils. 

1945.  The  salts  of  narcotina  may  be  obtained  by  dissolving  it  in  ^ned°b" 
dilute  acids  and  concentration. 

1946.  It  may  be  introduced  into  the  stomach  without  producing 
any  deleterious  or  even  sensible  effect.  Orfila  administered  it  to  the 

* Delphinia  exists  in  the  delphinium,  staphysagria,  or  stavesacre. 

+ Enietia  or  Emetina  is  obtained  from  the  various  roots  sold  under  the  name  of  ipe-  Emetia. 
cacuanha.  These  are  the  roots  of  the  cephoelis  ematica,  callicocca  ipecacuanha , and 
viola  emetica.  T.  263.  t Ann.  de  Chim.  xlv.  257. 

§Jour.  de  Pharm.  xxii.  382. 


438 


Chap  VII. 


Morphia. 


Action  of 
nitric  acid 
and  heat. 


Process. 


Action  on 
animals. 


Detection 
of  morphia, 


Vegetable  Alkalies. 

amount  of  several  drachms  a day,  without  perceiving  any  action 
whatever.  It  was  speedily  fatal  however  to  dogs. 

1947.  Morphia — Morphina.  C^H^NOs,  - 284.  This  is  one  of 
the  most  important  of  the  vegetable  alkalies,  and  the  principle  on 
which  the  narcotic  properties  of  opium  depend  ; insoluble  in  cold 
water;  boiling  water  dissolves  about  of  its  weight  of  it;  dis- 
solved by  boiling  alcohol,  crystallizing  in  six  and  four-sided  prisms, 
tasteless  when  pure.  Extremely  bitter  when  rendered  soluble  by 
alcohol  or  an  acid. 

1948.  Nitric  acid  changes  its  colour  to  orange-red,  which  gradu- 
ally passes  into  yellow.  By  heat  the  transparent  crystals  lose 
per  cent,  of  water  and  become  opaque  and  white.  If  the  heat  is 
increased  the  morphia  melts,  and  forms  a yellow  liquid,  which  be- 
comes white  and  crystalline  on  cooling:  by  continuing  the  heat,  it 
gives  out  a resinous  odour,  and  burns  with  a red  flame. 

1949.  Morphia  is  obtained  by  various  processes  ;*  the  following 
is  recommended  by  Thomson  : 

Macerate  opium  in  twice  its  weight  of  water  for  24  hours,  agitating  the  mix- 
ture occasionally  to  promote  solution.  Decant  and  pour  over  the  undissolved 

Eortion  a new  quantity  of  distilled  water,  equal  to  the  portion  first  employed. 

Lepeut  this  process  four  times,  or  till  everything  soluble  in  cold  water  be  taken 
up.  If  the  opium  be  of  good  quality,  about  three  fourths  of  it  will  be  dissolved 
and  the  remaining  fourth  remains  in  a solid  state.  Filter  the  solutions  thus  ob- 
tained, and  evaporate  the  whole  to  dryness  in  a low  heat  to  prevent  any  portion 
of  the  residue  from  being  decomposed  or  injured.  Pour  distilled  water  upon  this 
dry  residue.  The  whole  will  dissolve  except  a brilliant  crystalline  matter, 
which  is  narcotina.  Heat  the  solution  to  the  temperature  of  212°  and  add  to  it 
ammonia  in  slight  excess.  Boil  the  mixture  for  ten  minutes,  to  drive  off  this  ex- 
cess, and  then  allow  the  liquid  to  cool.  The  morphia  precipitates  in  crystals, 
pretty  pure  ; but  a portion  of  it  swims  on  the  surface,  mixed  with  impurity  If 
the  morphia  thus  obtained  be  digested  in  sulphuric  ether,  a portion  of  narcotina 
is  dissolved,  and  the  morphia  is  rendered  more  pure.  It  may  be  rendered  quite 
pure  by  dissolving  it  in  boiling  alcohol,  digesting  the  solution  with  ivory  black, 
filtering  and  crystallizing  This  process  should  be  repeated  three  or  four  times, 
in  order  to  free  the  morphia  from  all  impurity.  An  easier  mode  of  purifying  it 
is  to  dissolve  it  in  sulphuric  acid,  taking  care  to  avoid  an  excess  of  acid.  By 
evaporation  the?  sulphate  of  morphia  is  obtained  in  crystals.  Let  this  salt  be  de- 
composed by  digesting  it  with  magnesia  The  sulphate  of  magnesia  is  washed 
off,  and  the  morphia,  which  is  mixed  with  the  excess  of  magnesia  employed,  is 
to  be  dissolved  in  boiling  alcohol,  and  crystallized. 

Opium  yields  at  an  average  about  of  its  weight  of  pure  mor- 
phia. 

1950.  When  pure,  owing  to  its  insolubility,  it  is  almost  inert ; 
for  Orfila  gave  twelve  grains  of  it  to  a dog  without  its  being  fol- 
lowed by  any  sensible  effect.  In  a state  of  solution,  on  the  contrary, 
it  acts  on  the  animal  system  with  great  energy,  Sertuerner  having 
noticed  alarming  symptoms  from  so  small  a quantity  as  half  a grain. 
From  this  it  appears  to  follow  that  the  effects  of  an  over-dose  of  a 
salt  of  morphia  may  be  prevented  or  diminished  by  giving  a dilute 
solution  of  ammonia,  or  an  alkaline  carbonate,  so  as  to  precipitate 
the  vegetable  alkali. 

1951.  Many  experiments  have  been  made  to  discover  a ready 
mode  of  detecting  morphia,  and  distinguishing  it  from  other  bodies. 
When  this  alkaline  substance,  or  any  of  its  salts,  is  placed  in  contact 


* For  which  see  B.  ii.  532  ; Edin.  Med.  and  Surg.  Jour.  Nos.  107  and  111;  Amer. 
Jour.  xiii.  27. 


439 


Acetate  of  Morphia. 

with  a neutral  solution  of  a neutral  salt  of  peroxide  of  iron,  it  strikes  a sect>  i. 
blue  colour.  The  addition  of  a slight  excess  of  acid  causes  this  co- 
lour to  disappear  immediately.  The  addition  of  too  much  water 
causes  the  blue  colour  to  pass  into  red. 

1952.  When  opium  is  administered  as  a poison,  its  presence  is 
rendered  obvious  by  the  peculiar  odour  of  that  drug,  as  well  as  by  the 
red  tint  given  to  persalts  of  iron  by  the  meconic  acid  of  the  opium  ; 
but  when  death  is  occasioned  by  a salt  of  morphia,  it  becomes  neces- 
sary to  eliminate  the  morphia,  a practical  process  of  considerable  de- 
licacy. The  method  suggested  by  Lassaigne  for  detecting  acetate  Lassaigne’s 
of  morphia,  may  be  applied  to  its  saline  combinations  in  general.'*  rnethod. 

The  suspected  solution  is  evaporated  by  a temperature  of  212°,  and  the  residue 
treated  with  alcohol,  by  which  the  salt  of  morphia,  together  with  osmazome  and 
some  salts,  is  dissolved.  The  alcohol  is  next  evaporated,  and  water  added  to 
separate  fatty  matter.  The  aqueous  solution  is  then  set  aside  for  spontaneous 
evaporation,  during  which  the  salt  of  morphia  is  generally  deposited  in  crystals. 

From  an  aqueous  solution  of  the  salt,  ammonia  throws  down  a crystalline  precipi- 
tate, which  may  be  recognised  as  morphia  by  the  combination  of  the  following 
characters  : — By  the  figure  of  its  crystals;  its  bitter  taste  ; solubility  in  alcohol ; 
alkalinity  ; by  the  orange-red  tint  developed  by  nitric  acid  ; and  by  the  peculiar 
action  of  iodic  acid.  The  last  character  is  particularly  valuable  in  distinguishing 
morphia  from  other  vegetable  alkalies : the  latter  combine  with  iodic  acid  and 
form  iodates  ; but  morphia  decomposes  iodic  acid,  and  sets  iodine  free,  which 
may  then  be  delected  by  starch.  A grain  of  morphia  in  7000  grains  of  water 
may  be  discovered  by  this  test.f  T. 

1953.  Hydrochlorate  of  Morphia.  This  salt  is  much  employed  in  Hydro-^ 
Edinburgh  as  a medicine.!  It  crystallizes  in  needles,  and  dissolves  c 

in  from  15  to  20  times  its  weight  of  cold,  and  in  less  than  its  weight 
of  boiling  water. 

1954.  Acetate  of  Morphia  is  less  convenient  in  medical  practice  Acetate, 
than  the  foregoing  salt,  being  variable  in  constitution.  It  is  apt  to 

lose  a portien  of  its  acid,  even  when  kept  in  crystals  ; and  during 


* Ann.  de  Chim ..  et  de  Pfiys.  xxv.  102. 

t Serullas.  Robinet,  in  Jour,  de  Pharm.  x iii.24.  For  Hare’s  method  of  detecting 
minute  quantities  of  opium,  see  Amer.  Jour.  xii.  290. 

tThe  method  of  preparing  it  now  in  general  use  was  suggested  by  Robertson,  and  Gregory'*  pro- 
improved  by  Gregory  and  Robiquet,  Edin.  Med.  and  Surg.  Jour.  Nos.  107  and  111,  chlorate ofydro' 
and  Jour,  de  Pharm.  xix.  156.  The  aqueous  solution  of  opium  is  concentrated  in  a morphia, 
vessel  of  tinned  iron,  to  the  consistence  of  a thin  syrup,  when  a slight  excess  of  chloride 
of  calcium,  neutral,  and  quite  free  from  iron,  is  added.  The  mixture  is  boiled  fora 
few  minutes,  and  then  poured  into  an  evaporating  basin.  Resinous  flocks,  meconate 
of  lime,  and  colouring  matter  precipitate.  But  this  last  matter  does  not  separate  well 
unless  the  liquid  has  been  sufficiently  concentrated.  After  this  deposit  has  subsided, 
the  clear  liquid  is  evaporated  on  the  sand-bath.  During  the  evaporation  a new  depo- 
sition takes  place,  which  must  be  separated  before  the  liquid  be  allowed  to  crystallize. 

The  concentrated  liquid  is  now  to  be  allowed  to  cool,  under  constant  agitation.  The 
crystals  of  hydrochlorate  of  morphia  are  deposited  in  abundance.  They  are  to  be  put 
into  a stout  cloth,  and  subjected  to  pressure,  which  squeezes  out  a black  liquid,  con- 
taining various  impurities.  The  crystals  are  now  to  be  dissolved  in  water,  at  70°, 
filtered  through  cloth,  mixed  with  a little  chloride  of  calcium,  crystallized  and  com- 
pressed as  before.  These  crystals  are  again  dissolved  in  water,  the  liquid  is  satu- 
rated with  chalk  and  animal  charcoal  being  added,  the  whole  is  digested  for  24  hours 
at  194°.  It  is  then  filtered  and  concentrated.  The  crystals  are  deposited  rapidly,  and 
when  freed  from  the  mother  water  they  are  white  and  neutral.  The  salt  thus  ob- 
tained iw  dried  at  a temperature  of  150°.  It  usually  amounts  to  about  one  tenth  of 
the  weight  of  opium  employed,  and  consists  of  hydrochlorate  of  morphia  and  a little 
hydrochlorate  of  codeina;  from  which  it  might  probably  be  freed  by  digesting  in 
ether.  T.  Org.  Bodies,  271. 


440 


Vegetable  Alkalies. 


Chap.  VII. 
Codeia. 


Narceia. 

Thebaia. 

Meconia. 

Characters. 

Brucia. 

Conia. 

Parillia. 


the  evaporation  crystals  of  morphia  are  sometimes  deposited.  It  is 
readily  formed  by  dissolving  morphia  in  acetic  acid.* * * § 

1955.  Codeia  was  discovered  in  1832,  by  Robiquet,  in  the  hydro- 
chlorate of  morphia  made  by  Gregory’s  process.  (1953  n.)  Ammonia 
added  to  a solution  of  this  substance  in  water  precipitates  the  mor- 
phia, leaving  the  codeia  in  solution,  which  can  be  separated  by 
crystallization.  It  has  an  alkaline  reaction,  fuses  when  heated  to 
300°,  does  not  render  nitric  acid  red,  and  is  more  soluble  in  water 
than  morphia. 

1956.  In  doses  of  from  4 to  6 grains  it  produces  an  excitement 
similar  to  intoxication,  which  is  followed  by  depression,  nausea,  and 
vomiting. 

1957.  Narceia}  is  another  alkali  discovered  by  Pelletier  in  the 
watery  infusion  of  opium.  It  is  white  and  crystalline,  melting  at 
about  200°.  Its  salts  are  blue  when  dissolved  in  a particular  quan- 
tity of  water,  the  colour  changing  to  violet  and  red  as  it  is  increased. 

1959.  Thebaia  is  the  name  of  an  alkaline  principle  found  in  opium, 
which  is  considered  the  same  as  the  paramorphine  of  Pelletier.  It  is 
white,  crystalline,  soluble  in  ether,  and  fuses  at  266°. 

1959.  Meconia.  C^HsC)*.  This  is  another  constituent  of  opium, 
but  is  not  possessed  of  alkaline  properties,  and  contains  no  nitrogen. 
It  is  found  in  minute  quantity,  opium  yielding  but  about  of  its 
weight  of  meconia.  It  is  white,  has  no  odour,  and  when  first  put 
into  the  mouth  has  no  taste,  but  soon  imparts  an  impression  of  acri- 
dity. It  is  soluble  in  water,  alcohol  and  ether.  It  fuses  at  194°. 
It  resembles  fat  in  appearance.! 

1960.  Brucia  or  Brucina  resembles  strychnia  (1940),  and  may  be 
procured  from  the  nux  vomica  in  small  quantity,  and  also  from  the 
Brucia  ant  i-dy  sent  erica.*}  Like  morphia,  it  strikes  a deep  red  tint 
with  nitric  acid,  and  strychnia,  which  produces  this  effect,  is  consi- 
dered as  containing  a small  portion  of  brucia.  It  acts  upon  animats 
like  strychnia,  but  is  a less  active  poison.  It  is  intensely  bitter. 

1961.  Conia  is  the  active  principle  of  conium  maculatum , or  hem- 
lock, and  next  to  hydrocyanic  acid,  the  most  virulent  poison  known. || 

1962.  Parillia  or  Parillina  exists  in  the  root  of  smilax  sasaparilla, 
common  sasaparilla  of  commerce.  It  is  white,  of  a peculiar  odour, 


* The  basis  of  Battley’s  sedative  liquor  is  supposed  to  be  acetate  of  morphia- 

t Probably  from  vaQxrj,  torpor. 

t From  40  lbs.  of  opium  Couerbe  obtained 

50  ounces  of  morphia, 
l£  “ codeia, 

I “ thebaia, 

1 “ meconia, 

§ “ narceia. 

Colour  produced  by  agitating  the  preceding  substances  with  sulphuric  acid  mixed 
with  a little  nitric  acid  : 

Morphia  gives  a brownish  colour. 

Codeia  “ green  “ 

Thebaia  “ yellow  rose  “ 

Meconia  “ turmeric  yellow  and  then  a red 
Narceia  “ chocolate  “ (Reid.) 

§ False  angustura,  the  seeds  of  which  were  brought  from  Abyssinia  by  the  traveller 
Bruce. 

||  See  Christison  in  Trans.  Edin.  Boy.  Soc.  xiii. 


Alcohol . 


441 


a sharp  bitter  taste,  and  nauseous.  When  swallowed  to  the  extent  Sect,  xt. 
of  13  grains,  it  occasions  nausea,  vomiting,  diminishes  the  rapidity 
of  the  pulse,  and  acts  as  a sudorific. 

1963.  Nicotina  exists  in  the  leaves  and  seeds  of  tobacco.  At  Nicotina. 
common  temperatures  it  is  a liquid  of  the  consistence  of  honey,  of 
an  acrid  taste  and  a brown  colour.  It  is  a virulent  poison.  Its  salts 
are  distinguished  by  their  taste  of  tobacco  and  their  acrid  causticity* 

Section  II.  Intermediate  Bodies . 


1964.  In  this  class,  which  is  merely  temporary,  Thomson  has 
placed  all  the  vegetable  principles  which  seem  capable  of  entering 
into  definite  compounds  with  other  bodies,  and  which  have  not  as 
yet  been  proved  by  satisfactory  experiments  to  be  either  acid  or 
alkaline. 

Alcohol  and  its  Compounds. 

1965.  Alcohol , C4H50+H0,  eq.  46.00,  is  the  intoxicating  ingre-  Alcohol, 
dient  of  all  spirituous  and  vinous  liquors.  It  does  not  exist  ready 
formed  in  plants,  but  is  a product  of  the  vinous  fermentation. 

1966.  Common  alcohol  or  spirit  of  wine  is  prepared  by  distilling  Spirit  of 
whiskey  or  some  ardent  spirit,  and  the  rectified  spirit  of  wine  is  wme- 
procured  by  a second  distillation.  The  former  has  a sp.  gr.  of 
about  0.867,  and  the  latter  of  0.835  or  0.84.  In  this  state  it  contains 

a quantity  of  water,  from  which  it  may  be  freed  by  the  action  of 
substances  which  have  a strong  affinity  for  that  liquid. 

Thus,  when  carbonate  of  potassa  heated  to  300°  is  mixed  with  spirit  of  wine,  purjfied. 
the  alkali  unites  with  the  water,  forming  a dense  solution,  which,  on  standing, 
separates  from  the  alcohol,  so  that  the  latter  may  be  removed  by  decantation. 

To  the  alcohol,  thus  deprived  of  nart  of  its  water,  fresh  portions  of  the  dry  carbo- 
nate are  successively  added,  until  it  falls  through  the  spirit  without  being  moist- 
ened. Other  substances,  which  have  a powerful  attraction  for  water,  may  be 
substituted  for  carbonate  of  potassa.  Gay-Lussac  recommends  the  use  of  pure 
Jime  and  baryta ;+  and  dry  alumina  may  also  be  employed. 

A very  convenient  process  is  to  mix  the  alcohol  with  chloride  of  calcium  in 
powder,  or  with  quicklime,  and  draw  off  the  stronger  portions  by  distillation. 

Another  process,  which  has  been  recommended  for  depriving  alcohol  of  water,  is 
to  put  it  into  the  bladder  of  an  ox,  and  suspend  it  over  a sand-bath. 

The  strongest  alcohol  which  can  be  procured  by  any  of  these  pro- 
cesses has  a sp.  gr.  of  0.796  at  60°  F.  This  is  called  absolute  alco- 
hol, to  denote  its  entire  freedom  from  water. 


*The  following  table  exhibits  the  quantity  of  this  substance  yielded  by  1000  parts 
of  various  kinds  of  tobacco : 

Cuba  . „ . . *8.64 

Maryland  ....  5.28 

Virginia  .....  10.00 

He  de  Vilain  . . . . 11.20 

Lot  . . . . 6.48 

North  . . . 11.28 

Lot-et  Garonn  . . . .8  20 

For  smoking  ....  3.86 

T.  Organic  Bodies,  286, 

Several  other  principles  analogous  to  the  foregoing,  have  been  obtained  from  vari- 
| ous  plants,  on  which  their  activity  depends.  These  have  been  particularly  described 
i together  with  the  processes  for  obtaining  them  in  Thomson’s  late  volume, 
t An.  de  Ch.  lxxxvi.  t Jour  de  Soi.  xviii. 


442 


Chap  VII. 

Absolute 

■lcohol. 


Soemer- 
ing’s  ex- 
periments. 

Christi- 
son’s  ex- 
periments. 


Properties. 


Effect  of 
cold. 


Organic  Chemistry — Intermediate  Bodies. 

1967.  An  elegant  and  easy  process  for  procuring  absolute  alcohol, 
has  been  proposed  by  Graham.*  A large  shallow  basin  is  covered 
to  a small  depth  with  quicklime  in  coarse  powder,  and  a smaller  one 
containing  three  or  four  ounces  of  commercial  alcohol  is  supported 
just  above  it.  The  whole  is  placed  upon  the  plate  of  an  air-pump, 
covered  by  a low  receiver,  and  the  air  withdrawn  until  the  alcohol 
evinces  signs  of  ebullition.  Little  alcohol  evaporates,  as  its  vapour 
is  not  condensed  by  lime,  but  all  the  water  evaporates  and  its  vapour 
is  absorbed  by  the  lime.  Common  alcohol  is  in  this  way  entirely 
deprived  of  water  in  the  course  of  about  five  days.  The  tempera- 
ture should  be  preserved  as  uniform  as  possible  during  the  process. 
Sulphuric  acid  cannot  be  substituted  for  quicklime,  since  both  va- 
pours are  absorbed  by  this  liquid. 

1968.  According  to  Soemering  when  spirit  of  wine  is  enclosed  in 
a bladder,  and  exposed  for  some  time  to  the  air,  it  is  converted  into 
alcohol,  the  water  only  escaping  through  the  coats  of  the  bladder.t 
But  the  recent  experiments  of  Christison  do  not  confirm  this,  who 
found  that  spirit,  whatever  its  strength,  became  weaker  when  thus 
exposed.  They  however  confirm  the  results  obtained  by  Graham, 
and  absolute  alcohol  of  the  density  of  .796  was  obtained  in  two 
months  by  exposing  rectified  spirit  in  an  open  cup  enclosed  in  a con- 
fined space  with  quicklimeT 

1969.  Alcohol,  obtained  by  slow  and  careful  distillation,  is  a lim- 
pid, colourless  liquid,  of  an  agreeable  smell,  and  a strong  pungent 
flavour.  Its  specific  gravity  varies  with  its  purity  ; the  purest  ob- 
tained by  rectification  over  chloride  of  calcium  being  .791  ; as  it 
usually  occurs  it  is  .820  at  60°.  If  rendered  as  pure  as  possible  by 
simple  distillation,  it  can  scarcely  be  obtained  of  a lower  specific  gra- 
vity than  .825,  at  60°.  Absolute  alcohol  boils  at  168^-°  F.§ 

1970.  Hutton  is  said  to  have  succeeded  in  freezing  alcohol,  but 
the  fact  is  doubtful,  as  the  means  by  which  he  effected  its  congela- 
tion were  never  disclosed.  Walker  exposed  it  to  a temperature  of 
— 91  but  no  congelation  took  place.  Even  when  diluted  with  an 
equal  weight  of  water,  it  requires  a cold  of  6°  below  0 to  congeal  it. 
When  of  a specific  gravity  of  .810,  it  boils  at  the  temperature  of 
173.5°,  the  barometrical  pressure  being  30  inches.  In  the  vacuum  of 
an  air-pump  it  boils  at  common  temperatures. 

1971.  Alcohol  may  be  mixed  in  all  proportions,  with 
water,  and  the  specific  gravity  of  the  mixture  is  greater 
than  the  mean  of  the  two  liquids,  in  consequence  of  a di- 
minution of  bulk  that  occurs  on  mixture,  as  may  be  shown 
by  the  following  experiment : 

Fig.  190  represents  a tube  with  two  bulbs,  communicating  with 
each  other,  the  upper  one  being  supplied  with  a well  ground  glass 
stopper.  Fill  the  tube  and  lower  bulb  with  water,  pour  alcohol 
slowly  into  the  upper  bulb,  and  when  full  put  in  the  stopper.  The 
vessel  will  now  be  completely  filled,  the  alcohol  lying  upon  the  wa- 
ter; if  it  be  inverted,  the  alcohol  and  water  will  slowly  mix  and  the 


Fig.  190- 

§ 


* Edin.  Phil.  TVans.  1S28. 

t Quart.  Jour.  viii.  331,  and  Henderson’s  Hist,  of  Wines,  Lond.  1824. 
t Edin.  Phil.  Jour.  July,  1839.  § Ure. 


Alcohol. 


443 


. 

condensation  that  ensues  will  be  indicated  by  the  empty  space  in  the  tube.  A Sect.  11. 
considerable  rise  of  temperature  takes  place  in  this  experiment  in  consequence  of 
the  condensation. 


1972.  The  strength  of  such  spirituous  liquors  as  consist  of  little  Strength 
else  than  water  and  alcohol,  is  of  course  ascertained  by  their  specific  tained. 
gravity  ; and  for  the  purpose  of  levying  duties  upon  them,  this  is  as- 
certained by  the  hydrometer.*  But  the  only  correct  mode  of  ascer- 
taining the  specific  gravity  of  liquids,  is  by  weighing  them  in  a deli- 
cate balance  against  an  equal  volume  of  pure  water,  of  a similar 
temperature.!  Proof  spirit  contains  equal  weights  of  alcohol  and 
water  ; sp.  gr.  0.917. 

1873.  There  are  other  methods  of  judging  of  the  strength  of  spi- 
rituous liquors,  which,  though  useful,  are  not  accurate,  such  as  the 
taste,  the  size  and  appearance  of  the  bubbles  when  shaken,  the  sink- 
ing or  floating  of  olive  oil  in  it,  and  the  appearances  exhibited  when 
burned  ; if  it  burns  away  perfectly  to  dryness,  and  inflames  gunpow- 
der or  a piece  of  cotton  immersed  in  it,  it  is  considered  as  alcohol: 
the  different  spirituous  liquors  leave  variable  proportions  of  water 
when  thus  burned  in  a graduated  vessel. 

1974.  Alcohol  is  extremely  inflammable,  and  burns  with  a pale  c'ombus- 
blue  flame,  scarcely  visible  in  bright  daylight.  It  occasions  no  fuli-  tion  of  al- 
ginous  deposition  upon  substances  held  over  it,  and  the  products  ofcoho1- 
its  combustion  are  carbonic  acid  and  water,  the  weight  of  the 
water  considerably  exceeding  that  of  the  alcohol  consumed.  Ac- 
cording to  Saussure,  jun.,  100  parts  of  alcohol  afford,  when  burned, 

136  parts  of  water,  the  production  of  which  may  be  shown  by  sub- 
stituting the  flame  of  alcohol  for  that  of  hydrogen,  in  the  apparatus 
described  in  Chapter  iii.,  under  the  article  Water  (403),  and 
if  the  tube  at  its  extremity  be  turned  down  into  a glass  jar,  it  will  be 
found  that  a current  of  carbonic  acid  pisses  out  of  it,  which  may  be 
rendered  evident  by  lime  water. 

There  are  some  substances  which  communicate  colour  to  the 


flame  of  alcohol ; from  boracic  acid  it  acquires  a greenish-yellow 
tint ; nitre  and  the  soluble  salts  of  baryta  cause  it  to  burn  yellow, 
and  those  of  strontia  give  it  a beautiful  rose  colour ; cu-  Fig.  191. 
preous  salts  impart  a fine  green  tinge. 

1975.  Alcohol  dissolves  pure  soda  and  potassa,  but  it 
does  not  act  upon  their  carbonates : consequently,  if  the 


* The  hydrometer  of  Bate,  constructed  for  the  Commissioners  of  Great 
Britain,  has  a scale  of  4 inches  in  length  divided  into  100  parts  and  9 
weights,  giving  a range  of  900  divisions,  and  expresses  specific  gravities  at 
the  temperature  of  62°  F.  To  render  this  instrument  so  accurate  as  to  in- 
volve no  error  of  appreciable  amount,  the  weights  are  constructed  so  that 
each  successive  weight  has  an  increase  of  bulk  over  the  preceding  weight 
equal  to  that  part  of  the  stem  occupied  by  the  scale,  and  an  increase  of 
weight  sufficient  to  take  the  whole  of  the  scale,  and  no  more,  down  to  the  J k. 
liquid.  Fig.  191  represents  this  instrument  and  two  of  its  nine  ballast  / \ 

weights.  It  comprehends  all  specific  gravities  between  820  and  1000  and 
indicates  true  sp-  gr.  with  almost  perfect  accuracy  at  62°  F.  Ure’s  Did.  \ J 
Arts  and  Manuf.  23.  \ / 

In  France  the  alcoometre  of  Gay-Lussac  is  employed,  for  which  see  Ibid.  j I 
In  the  United  States  the  hydrometer  of  Dicas  is  used.  j l 

t In  the  Phil.  Trans,  for  1794,  Gilpin  has  given  a copious  and  valua- 
ble  series  of  tables  of  the  specific  gravity  of  mixtures  of  alcohol  and  water,  f q 
and  of  the  condensation  that  ensues,  with  several  other  particulars.  Other  \ J 
tables  by  Tralles  and  Gay-Lussac,  will  be  found  in  Ure’s  Did.  Arts  and  \ I 
Manuf.  18—24.  v 


\ 


Use  as  a 
solvent. 


Bale’s  hydrom.- 
eter. 


444 


Organic  Chemistry — Intermediate  Bodies. 


Alcohates. 


Chap,  vii.  latter  be  mixed  with  alcohol  containing  water,  the  liquor  separates 
into  two  portions,  the  upper  being  alcohol  deprived  to  a considera- 
ble extent,  of  water,  and  the  lower  the  aqueous  solution  of  the 
carbonate.  The  alcoholic  solution  of  caustic  potassa  was  known  in 
old  pharmacy  under  the  name  of  Van  Helmont’s  Tincture  of  Tar - 
tartar*”  °*tar'  ^ts  llse  *n  Purifying-  potassa  has  already  been  stated  (845). 

1976.  The  greater  number  of  sulphates  are  insoluble  in  this  men- 
struum, but  it  dissolves  many  of  the  hydrochlorates  and  nitrates.  It 
also  dissolves  the  greater  number  of  the  acids.  It  absorbs  many 
gaseous  bodies.  It  dissolves  the  vegetable  acids,  the  volatile  oils, 
the  resins,  tan,  and  extractive  matter,  and  many  of  the  soaps ; the 
greater  number  of  the  fixed  oils  are  taken  up  by  it  in  small  quanti- 
ties only,  but  some  dissolve  largely.* 

1977.  Graham  has  shown  that  alcohol  may  in  many  instances 
be  combined  with  saline  bodies,  performing  as  it  were  the  part  of 
water  of  crystallization.  Such  combinations  may  be  termed  alco- 
hates. They  are  obtained  by  dissolving  the  substances  by  heat  in 
absolute  alcohol,  and  are  deposited  as  the  solution  cools,  mor*  or  less 
regularly  crystallized.  They  appear  to  be  definite  compounds,  and 
in  some  of  them  the  alcohol  is  retained  by  an  attraction  so  powerful, 
as  not  to  be  evolved  at  a temperature  of  400°  or  500°. t 

1978.  When  the  vapour  of  alcohol  is  passed  through  a red-hot 
copper  tube,  it  is  decomposed,  a portion  of  charcoal  is  deposited,  and 
a large  quantity  of  carburetted  hydrogen  gas  is  evolved. 

1979.  Alcohol  exists  ready  formed  in  wine  and  spirituous  liquors, 
and  may  be  collected  without  heat.  Brandet  procured  it  from  wine 
by  precipitating  the  acid  and  extractive  colouring  matters  by  suba- 
cetate of  lead,  and  then  depriving  the  alcohol  of  water  by  dry  carbo- 
nate of  potassa : the  pure  alcohol  may  then  be  measured  in  a 
graduated  tube.  Gay-Lussac  obtained  alcohol  from  wine  by  distil- 
ling it  in  vacuo  at  the  temperature  of  60°  F.  He  also  succeeded  in 
separating  the  alcohol  by  the  method  of  Brande  ; but  he  suggests 
the  employment  of  litharge  in  fine  powder,  instead  of  subacetate  of 
lead,  for  precipitating  the  colouring  matter.^ 

1980.  The  preceding  researches  of  Brande  led  him  to  examine 
the  quantity  of  alcohol  contained  in  spirituous  and  fermented  liquors. 
According  to  his  experiments,  brandy,  rum,  gin,  and  whiskey,  con- 
tain from  51  to 54  percent,  of  alcohol,  of  specific  gravity  0.825.  The 
stronger  wines,  such  as  Lissa,  Raisin  wine,  Marsala,  Port,  Madeira, 
Sherry,  Tenerifle,  Constantia,  Malaga,  Bucellas,  Calcavella,  and  Vi- 
donia,  contain  from  between  18  or  19  to  25  per  cent,  of  alcohol.  In 
Claret,  Sauteme,  Burgundy,  Hock,  Champagne,  Hermitage,  and 
Gooseberry  wine,  the  quantity  is  from  12  to  17  per  cent.  In  cider, 
perry,  ale,  and  porter,  the  quantity  varies  from  4 to  near  10  per 
cent.  In  all  spirits,  such  as  brandy  or  whiskey,  the  alcohol  is  sim- 
ply combined  with  water;  whereas  in  wine  it  is  in  combination  with 


Decom- 

position. 

Alcohol  in 


Brande’s 

results. 


* It  may  be  remarked  that  many  errors  exist  in  the  published  estimates  of  the  solu- 
bility of  substances  in  alcohol,  arising  from  the  existence  of  water  either  in  the  solvent 
or  substance  dissolved. 

t Graham  has  examined  the  alcoholic  combinations  of  chloride  of  calcium,  nitrate 
of  magnesia,  Ate.  see  Quart.  Jour.,  N.  S.,  Dec.  1828. 
t Phil.  Trans.  181 1 and  1813.  § Mem.  d'Arcueil,  vol.  iii. 


Alcohol. 


445 


mucilaginous,  saccharine,  and  other  vegetable  principles,  a condition  Sect,  u. 
which  tends  to  diminish  the  action  of  the  alcohol  upon  the  system.* 

1981.  From  recent  experiments  Christison  is  of  opinion  that  the  christi- 
alcoholic  strength  of  many  wines  has  been  overrated.  The  follow- son’s  recent 
ing  table  shows  some  of  his  results;  the  first  column  gives  the  per- Cents' 
centage  of  absolute  alcohol  of  sp.  gr.  793.9,  by  weight,  and  the 
second  the  per-centage  of  proof-spirit- sp.  gr.  920  by  volume. 


Alcohol  p.  c.  P. 

By  Wgh. 

Sp.  p . c. 

By  Vol. 

Port — weakest  .... 

14.97 

30.56 

mean  of  7 wines 

- 

16.20 

33.91 

strongest  - - £ 

17.10 

37.27 

white  port 

- 

14  97 

31.31 

Sherry — weakest  - 

13.98 

30.84 

mean  of  13  wines,  excluding  those  very  long 

kept  in  casks  - 

15.37 

33.59 

strongest  - 

- 

16.17 

35.12 

mean  of  9 wines  very  long  in  cask 

in 

the 

East  Indies 

- 

14.72 

32.30 

Madre  da  Xeres  - 

16.90 

37.06 

Madeira  \ a11  lonS  in  cask  in  X strongest 

14.09 

30.80 

Madeira  £ the  tast  Indies  $ weakest  - 

16.90 

36.81 

Teneriffe,  long  in  cask  at  Calcutta 

- 

13.84 

30.21 

Cercial  - 

15.45 

33.65 

Dry  Lisbon  - 

- 

16.14 

34.71 

Claret,  a first  growth  of  1811 

7.72 

16.95 

Chateau-Latour,  first  growth  1825 

- 

7.78 

17.  6 

Ordinary  Claret,  a superior  “ vin  ordinaire” 

8.99 

18.96 

Malmsey  - - 

- 

12.86 

28.37 

Rudesheimer,  superior  quality 

8.40 

18.44 

Do.  inferior 

. 

6.90 

15.19 

Giles’  Edin.  Ale  before  bottling 

5.70 

12.60 

Same  ale  2 years  in  bottle 

- 

6.06 

13.40 

Superior  London  Porter  4 months  bottled  - 

5.36 

1 1.91 t 

1982.  The  composition  of  alcohol  in 

the 

state  of  vapour 

is  thus  Composi- 

stated  by  Thomson  : 

tion  of  al- 
cohol va- 

1  vol.  olefiant  gas  . . . . 

0.9722  sp.  gr. 

pour  ac- 

1  “ vapour  of  water 

0.6250  “ 

cording  to 

Thomson, 

1.5972  “ 

condensed  into  1 vol. ; so  that  its  sp.  gr.  is  1.5972  when  in  the  state 
of  vapour. 

1983.  Olefiant  gas  is  a compound,  2 vols.  carbon  vapour,  and  2 
vols.  hydrogen  gas  united  together,  and  condensed  into  1 volume. 

So  that  a vol.  of  it  is  equivalent  to  2 atoms  of  carbon,  and  2 atoms 
hydrogen. 

1984.  Liebig  has  given  another  view  of  the  composition  of  alcohol,  Liebig’s 
founded  upon  the  experiments  lately  made  to  determine  the  compo- 
sition  of  ether.  According  to  him,  ether  contains  no  water,  but  is 
composed  of  C4H5-f-0,  or  it  is  an  oxide  of  (C4H5).  Alcohol  is  a hy- 
drate of  ether,  or  it  consists  of  (C4H50)-(-H0.  This  view  recom- 
mends itself  by  its  simplicity,  and  by  the  facility  which  it  presents  to 

us  in  explaining  the  nature  of  the  numerous  compounds  formed  by 
means  of  alcohol! 


* For  Brande’s  table  of  proportion  of  alcohol  in  wines,  see  his  Chem.  ii.  565. 
t Edin.  Philos.  Jour.  July,  1839.  t Thomson,  Org.  Bodies , 300. 


446 


Chap,  VII. 
Aldehyde. 

Obtained. 


By  spongy 
platinum. 


Properties. 


A solvent. 


Action  on 
oxide  of 
silver. 


Liebig’s 

analysis. 


Organic  Chemistry — Intermediate  Bodies. 

1185.  Aldehyde .*  This  remarkable  substance  was  first  noticed  by 
Dobereiner,  but  has  been  particularly  examined  by  Liebig,  t 

19S6.  It  is  a colourless  liquid,  having  a peculiar  ethereal  smell 
and  is  obtained  by  passing  the  vapour  of  ether  through  a large  glass 
tube  heated  to  redness.  The  products  being  introduced  into  sulphu- 
ric ether,  the  aldehyde  is  retained  in  combination.  Dry  ammoniacal  gas 
is  then  passed  into  the  solution,- which  forms  a crystalline  compound 
with  the  aldehyde,  termed  ammonia  aldehyde.  From  this  compound  it 
is  procured  by  adding  an  equal  weight  of  water,  and  then  diluted  sul- 
phuric acid  to  unite  with  the  ammonia,  heating  it  afterwards  in  a 
retort.!  The  product  of  distillation  is  hydrated  aldehyde,  which  is 
separated  from  the  water  by  distilling  it  from  chloride  of  calcium. 

1987.  Aldehyde  may  also  be  formed  by  the  action  of  spongy  pla- 
tinum with  air  and  alcohol,  or  by  distillation  from  4 parts  of  water 
and  4 of  alcohol,  mixed  with  6 of  peroxide  of  manganese,  and  6 of 
aqueous  sulphuric  acid. 

198S.  It  is  very  volatile,  of  sp.  gr.  0.790,  and  boiling  at  7l£°. 
Its  vapour  when  inhaled  produces  a kind  of  cramp  in  the  stomach. 
It  combines  with  water  in  all  proportions,  with  evolution  of  heat.  It 
takes  fire  readily,  burning  with  a pale  flame  and  much  light.  Kept 
in  a vessel  full  of  air  it  absorbs  oxygen,  and  is  converted  into  very 
concentrated  acetic  acid  ; this  is  promoted  by  spongy  platinum. 

1989.  Aldehyde  dissolves  sulphur,  phosphorus,  and  iodine  ; ab- 
sorbs chlorine  and  bromine  with  production  of  hydrochloric  and  hy- 
drobromic  acids. § 

1990.  When  heated  with  water  and  oxide  of  silver,  at  first  mode- 
rately and  then  raised  to  the  boiling  temperature,  in  a glass  tube,  the 
silver  is  revived  and  covers  the  glass  with  a brilliant  coating.  The 
oxide  of  silver  is  also  reduced  when  a few  drops  of  ammonia  are  ad- 
ded to  aqueous  aldehyde  and  it  is  heated  with  the  oxide,  affording  an 
easy  method  of  ascertaining  the  presence  of  the  smallest  quantity  of 
aldehyde  in  any  liquid. 

1991.  When  kept  in  vessels  to  which  air  has  access,  oxygen  is 
absorbed,  and  prismatic  crystals  are  formed,  which  fuse  at  212°,  and 
at  a higher  temperature  sublime.  They  are  hard,  inflammable,  and 
soluble  in  alcohol  and  ether. 

1992.  Liebig  analysed  aldehyde  by  heating  it  with  oxide  of  cop- 
per ; the  result  was  as  follows  : 

Carbon  - - 53  67  or  4 atoms  =3.0  or  per  cent.  54.55 

Hydrogen  - 8.97  or  4 “ = 0.5  or  “ 9.09 

Oxygen  - - 37.36  or  2 “ = 2.  or  “ 36.36 

100.00  5.5  100.00 


* From  alcohol  dehydratus. 

t Ann.  de.  Chim.  Ct  Phys.  lix.  296,  and  Ann.  de  Pharm.  xiv.  133. 
t For  minute  details,  see  T.  Organic  Bodies , 301. 

§ Liebig  is  of  opiuion  that  in  these  reactions  the  aldehyde  is  changed  into  chloral 
and  bromal. 


Acetal 


447 


The  density  of  its  vapour  he  found  1.532.*  Sect,  n. 

1993.  Aldehyde  resin  is  produced  when  potassa  is  dissolved  in  Aldehyde 
alcohol,  and  most  speedily  when  the  access  of  air  is  permitted.  It resitl- 

is  to  the  presence  of  this  substance  that  the  alcoholic  solution  of  po- 
tassa owes  its  reddish-brown  colour.  It  is  produced  also  when  a 
solution  of  potassa  in  alcohol  and  acetal  is  exposed  to  the  air.  This 
is  a useful  character  to  enable  us  to  distinguish  acetal  from  acetic 
ether  and  other  ethereal  liquids.  All  the  liquids  containing'  alde- 
hyde assume  a reddish-brown  colour  when  heated  with  potassa  ; and 
when  diluted  with  water  the  resin  of  aldehyde  separates  in  brown 
flocks. f 

1994.  Acetal  was  obtained  by  Dobereiner  by  the  following  pro-  Acetal, 
cess  : 

Place  alcohol  of  sp.  gr.  0.8631  upon  a saucer  and  in  the  saucer  a support,  the  Process, 
top  of  which  is  raised  a few  lines  above  the  alcohol ; upon  the  support  place  a 
number  of  watch-glasses  having  a quantity  of  spongy  platinum  in  each.  Cover 
the  whole  with  a bell  glass,  open  above,  standing  in  the  saucer  so  that  the  va= 
pours  which  condense  may  fall  back  into  the  alcohol.  The  apparatus  is  left  in  a 
place  not  too  cool  till  the  alcohol  acquires  a very  acid  taste.  The  whole  is  then 
distilled  over  carbonate  of  lime.  To  the  product  of  this  distillation  add  chloride 
of  calcium  in  powder,  which  causes  the  separation  of  an  ethereal  liquor,  to  which 
Liebig  has  given  the  name  of  acetal. 

1995.  Acetal  is  colourless,  and  of  sp.  gr.  0.823 ; it  boils  at  203°  ; Properties, 
burns  with  a bright  flame,  and  by  the  action  of  spongy  platinum  is 
converted  into  acetic  acid.  It  may  be  considered  as  C4H4  -f- 


* If  we  consider  the  vapour  as  composed  of  4 vols-  carbon  vapour,  4 vols.  hydrogen 
gas,  and  i vol.  oxygen  gas,  condensed  into  2 vols,  we  have 
4 vols.  carbon  vapour  =1.6666 
4 “ hydrogen  gas  =0.2777 
1 vol.  oxygen  =1.1111 


2)2-9555 
1.4777  = sp.  gr. 

of  aldehyde  vapour.  The  vapour  then  is  composed  of  4 vols.  carbon,  4 vols.  hydro- 
gen and  1 vol.  oxygen  condensed  into  2 vols. 

It  is  easy  to  see  how,  by  means  of  oxygen,  aldehyde  is  converted  with  such  facility 
into  acetic  acid, 

Acetic  acid  - - - C4H3O3 

Aldehyde  - - C4H4O2 

If,  therefore,  the  oxygen  combine  with  one  of  the  atoms  of  hydrogen,  and  convert  it 
into  water,  while  another  atom  of  oxygen  replaces  the  hydrogen,  it  is  obvious  that  al- 
dehyde will  become  acetic  acid.  Liebig  is  of  opinion  that  there  exists  an  unknown 
basis  composed  of  C4  H3,  to  which  he  has  given  the  name  of  alde-hyden.  The 
oxide  of  this  basis  is  C4  H3  O,  and  when  this  oxide  is  combined  with  an  atom  of  wa- 
ter, it  constitutes  aldehyde,  the  true  formula  for  which  is  C4  H3  0+ HO.  Acetic  acid 
is  C4  H3  O3  + HO.  It  is  obvious  also  that  aldehyde  and  alcohol  differ  from  each 
other  merely  by  the  aldehyde  containing  2 atoms  less  hydrogen  than  alcohol. 

Alcohol  is  - - C4  H6  62 

Aldehyde  is  - - C4  H4  O2.  (Thomson,  304.) 

f Aldehydic  Acid  is  prepared  from  aldehyde  and  oxide  of  silver,  and  is  composed  of  Aldeh  . 
C4H4.O3.  It  differs  from  acetic  acid  merely  iu  containing  an  additional  atom  of  hy-  e y lc  aci  ‘ 
drogen. 

Bromide  and  Iodide  of  Aldehyden  have  been  discovered,  for  which  see  T.  3^7. 
t For  some  other  compounds  see  T.  Org\  Bodies,  310.  Thomson  has  given  the 
name  of  deutocarbohy drogen  to  olefiant  gas,  and  shown  its  relation  to  aldehyden  as 
follows : 

Aldehyden  . . C4  H3 

Chloride  of  . . . C4  H3  -j-  Cl 

Bromide  of  “ . . C4  H3  + Br 


448 


Chap.  VII. 
Chloral. 

Properties, 

Insoluble 

chloral. 

Ethal. 


Ether. 


Sulphuric 

ether. 

Process. 


Chloroform. 


Bromoform. 


Organic  Chemistry — Intermediate  Bodies. 


1996.  Chloral*  was  discovered  by  Liebig.  It  is  obtained  by 
passing  a current  of  dry  chlorine  gas  through  absolute  alcohol.  A 
prodigious  quantity  of  chlorine  is  necessary  and  a great  deal  of  hy- 
drochloric acid  is  formed.! 

1997.  It  is  liquid,  colourless,  tasteless,  of  a penetrating  odour,  and 
of  an  oily  appearance.  It  combines  with  water,  sulphur,  bromine  and 
iodine  ; is  decomposed  when  heated  with  different  earths  and  metals, 
metallic  chlorides  being  formed.! 

1998.  Liebig  has  given  the  name  of  insoluble  chloral  to  the  sub- 
stance formed  when  chloral  is  left  to  the  action  of  concentrated  sul- 


phuric acid  at  common  temperatures.  During  the  conversion  of 
alcohol  into  chloral,  the  alcohol  loses  5 atoms  of  hydrogen  and  gains 
3 atoms  of  chlorine.  For  every  atom  of  alcohol  converted  into  chlo- 
ral 10  vols.  of  hydrochloric  acid  are  formed,  and  3 vols  of  chlorine 
enter  into  chemical  combination  with  it.  T. 

1999.  Ethnic  C16H170,  eq.  = 121.  This  substance  has  been  de- 
scribed by  Thomson  in  this  place  from  its  analogy  to  alcohol  and 
sulphuric  ether.  It  was  obtained  by  Chevreul  from  spermaceti  or 
cetine.  With  sulphuric  acid  it  forms  sulphocetic  acid. 

2000.  Ether.  This  name  has  been  given  to  the  light,  volatile, 
inflammable,  and  fragrant  liquids,  obtained  by  distilling  in  a glass 
retort  a mixture  of  alcohol  and  any  strong  acid.  The  different  kinds 
of  ether  have  been  distinguished  by  the  name  of  the  acid  employed 
in  the  process.  That  which  is  best  known  is  sulphuric  ether. 

192  To  prepare  sulphuric  ether,  equal  weights  of  sulphuric  acid  and  alcohol 

0 are  exposed  to  heat  in  a plain  glass  retort,  pouring  in  the  alcohol  first  and 
then  the  acid  by  a long  glass  funnel  (Fig.  192;,  and  adjusting  the  retort  in  a 
sand-bath  already  heated  to  the  temperature  of  200°,  in  the  manner  shown 


in  Fig.  193.  The  acid  and 
the  alcohol  should  be  well 
mixed  by  shaking  them  toge- 
ther in  the  retort,  when  the 
temperature  rises  considera- 
bly, and  the  receiver  should 
be  tubulated  to  convey  away 
the  atmospheric  arr,  and  any 
other  gaseous  products  that 
may  be  formed  towards  the 


Fig.  193. 


Iodide  of  aldehyden 

Olefiant  gas 

Chloride  of  deutocarbohydroeen 
Bromide  of  “ 

Iodide  of  “ 

Aldehyde 
Aldehydic  acid  • 

Acetic  acid 


C4  Hs  + I 
C4  H3  + H 
C4  Ha  Cl  + HC1 
C4  Ha  Br  + HBr 
C Hs  I + H I 
C4  H3  O -I-  HO 
C4  Ha  Oa  + HO 
C4  H3  03  + HO 

Chloroform  is  obtained  by  distilling  a mixture  of  alcohol  and  aqueous  solution  of 
bleaching  powder,  as  a limpid  fluid  of  sp.  gr.  1.430.  It  is  a compound  of  1 atom  bi- 
carhuret  of  hydrogen  with  3 atoms  of  chlorine. 

Bromoform  is  analogous  to  the  last  and  is  obtained  when  a mixtu-e  of  bromide  of 
lime  and  alcohol,  or  acetone,  is  distilled.  It  is  an  oily  looking  liquid,  heavier  than 
sulphuric  acid,  and  its  composition  is  the  same  as  that  of  chloroform. 


* From  chlorine  and  alcohol. 

+ If  we  employ  an  avoirdupois  pound  of  alcohol,  we  shall  require  66.453  cubic  inches, 
or  almost  38£  cubic  feet  of  chlorine  gas,  or  48  cubic  feet  of  hydrochloric  acid  gas.  T. 

t It  differs  from  chloroform  by  containing  two  atoms  more  of  carbon  and  two  atoms 
of  oxygen. 

§ From  first  syllables  of  ether  and  alcohol. 


Ether.  449 

close  of  the  operation.  The  neck  of  the  receiver  should  fit  closely  to  the  neck  Sect.  I. 
of  the  retort,  and  the  joint  he  rendered  tight  by  tying  it  round  with  a piece  of 
linen  or  cotton  cloth  spread  over  with  paste  made  of  flour.  The  bent  tube  fixed 
to  the  tubulure  of  the  receiver  should  be  made  to  pass  into  a second  receiver,  or 
to  dip  into  a bottle  in  the  manner  represented,  which  is  kept  cold  by  placing  it  in 
ajar  or  basin  with  water  or  ice  ; the  tube  must  not  fit  tightly  to  the  neck  of  the 
bottle,  but  allow  any  gas  that  may  come  over  to  be  freely  disengaged.  The  first 
receiver  should  be  tied  round  with  apiece  of  linen  or  cotton  cloth,  that  it  may  be 
more  easily  kept  cold  ; ice  or  snow  should  always  be  used  when  it  can  be  pro- 
cured. 

2001.  The  distillation  is  generally  continued  till  a quantity  of 
liquid  has  come  over  equal  to  one  half  the  alcohol  employed.  More 
ether  is  said  to  be  obtained  when  it  is  kept  constantly  boiling  than  at 
a lower  temperature,  though  this  has  been  disputed  ; the  retort 
should  not  be  filled  more  than  half  full,  and  great  attention  must  be 
paid  to  the  heat  applied  during  the  whole  of  the  operation,  as  the 
mixture  is  apt  to  boil  over  when  urged  with  too  strong  a fire. 

2002.  The  ether  that  condenses  in  the  receiver  is  never  obtained 

pure  at  first,  being  always  mixed  with  a little  alcohol  that  distils  Purified< 
over  unaltered,  and  some  sulphurous  acid.  To  remove  these,  it  is 
mixed  with  potassa,  taking  five  or  six  grains  for  every  ounce  of  alco- 
hol employed,  and  distilled  again  from  a retort  with  a very  gentle 
heat  till  five  or  six  sevenths  shall  have  passed  over  ; the  potassa  re- 
tains the  sulphurous  acid,  along  with  some  water  and  alcohol.  To 
separate  the  alcohol  completely,  it  maybe  shaken  with  about  three 
fourths  of  its  bulk  of  water,  which  combines  with  all  the  alcohol  and 
a little  ether.  It  is  then  distilled  by  a very  gentle  heat,  and  may  be 
rendered  still  stronger  by  distillation  from  chloride  of  lime.  It  should 
be  kept  in  bottles  with  well-ground  glass  stopples. 

On  a small  scale,  an  ounce  or  two  of  alcohol  with  as  much 
sulphuric  acid  by  weight,  will  be  sufficient  to  show  the  process,  con- 
densing the  product  in  a common  flask.* 

2003.  Ether  is  a colourless  liquid,  of  a hot  pungent  taste  and  fra-  properties, 
grant  odour.  It  is  highly  exhilarating,  and  produces  a degree  of 
intoxication  when  its  vapour  is  inhaled  by  the  nostrils.  Its  sp.  gr. 

varies  with  its  purity.  Lowitz  is  said  to  have  procured  it  as  light 
as  .632 ; Brande  states  that  he  never  obtained  it  lower  than 


*The  London  Pharmacop.  directs  the  distillation  of  ether  with  potassa,  for  its  pu- 
rification from  sulphurous  acid;  and  Phillips  has  given  the  following  d Sections  for  gg1s18lhps pr0‘ 
procuring  ether  for  pharmaceutical  purposes,  which  answer  extremely  well. 

“ Mix  with  16  ounces  of  sulphuric  acid,  an  equal  weight  of  rectified  spirit,  and  distil 
about  10  fluid  ounces,  add  8 ounces  of  spirit  !o  the  residuum  in  the  retort,  and  distil 
about  9 fluid  ounces ; or  continue  the  operation  until  the  contents  pf  the  retort  begin 
to  rise  or  the  product  becomes  considerably  sulphurous ; mix  the  two  products,  and  if 
the  mixture  consists  of  a light  and  heavy  fluid,  separate  them  ; add  potassa  to  the 
lighter,  as  long  as  it  appears  to  be  dissolved  ; separate  the  ether  from  the  solution  of 
potassa,  and  distil  about  nine  tenths  of  it,  to  be  preserved  as  ether  sulphuricus,  the 
specific  gravity  of  which  ought  to  be  at  most  .750.” 

In  the  preparation  of  ether  on  a large  scale  considerable  risk  is  incurred  by  fire, 
recourse  has  therefore  been  had  to  steam  as  the  source  of  the  requited  heat.  In  the 
apparatus  employed  at  Apothecaries’  Hall  (Lond.)  the  still  is  of  cast  iron,  lined  with 
lead  ; the  steam  is  conducted  through  the  mixture  of  acid  and  alcohol  by  a contorted 
leaden  pipe  at  the  bottom  of  the  still,  and  is  supplied  by  a boiler  calculated  to  resist 
the  pressure  of  190  lbs.  on  the  square  inch  ; in  this  way  the  mixture  is  very  rapidly 
raised  to  its  boiling  point,  and  a larger  relative  quantity  of  ether  is  obtained.  The 
boiler  is  placed  in  a distant  apartment.  The  condensing  apparatus  and  refrigeratory 
are  of  the  usual  construction,  but  abundantly  supplied  with  cold  water.  Brande’s 
Pharmacy,  456. 

57 


450 


Chap.  VII. 
Volatile. 

Exp. 

Boiling 

point 

Exp. 


Exp. 

Explodes 
witn  oxy- 
gen, 

Exp. 

And  with 
chlorine. 


Organic  Chemistry — Intermediate  Bodies. 


.700  ; as  ordinarily  prepared,  its  sp.  gr.  varies  between  .730  and 
.760,  and  as  met  with  in  commerce,  it  must  be  considered  as  a mix- 
ture of  pure  ether  and  alcohol.* * * § 

2004.  It  is  extremely  volatile,  and  when  poured  from  one  vessel 
into  another,  a considerable  portion  evaporates;  during  its  evapora- 
tion from  surfaces,  it  produces  intense  cold,  as  may  be  felt  by  pour- 
ing it  upon  the  hand  ; and  seen,  by  dropping  it  upon  the  bulb  of  a 
thermometer,  which  sinks  to  many  degrees  below  the  freezing  point. 
The  sp.  gr.  of  the  vapour  of  ether  compared  with  atmospheric  air, 
is,  according  to  Gay-Lussac,  as  2.586  to  l.OOO.t  Two  ounce  mea- 
sures of  ether  converted  into  gas  at  the  temperature  of  72.50  fill  the 
space  of  a cubic  foot. 

The  change  may  be  exhibited  by  placing  a large  bell  glass  filled  with  hot 
water  on  the  shelf  of  the  pneumatic  trough  and  passing  the  ether  from  a phial  up 
into  it.  The  vapour  will  fill  the  jar,  and  may  be  fired  with  suitable  precautions. 

2005.  At  mean  pressure,  sulphuric  ether,  when  of  a sp.  gr.  of 
.730,  boils  at  98°,  and  under  the  exhausted  receiver  of  an  air-pump, 
at  all  temperatures  above  — 20°  ; hence,  were  it  not  for  atmospheric 
pressure,  ether  would  only  be  known  in  the  state  of  vapour. 

In  consequence  of  the  cold  produced  during  the  vaporization  of 
sulphuric  ether,  the  phenomena  of  boiling  and  freezing  may  be  exhi- 
bited in  the  same  vessel. 


For  this  purpose  procure  a very  thin  flask  which  fits 
loosely  into  a wine-glass,  as  shown  in  Fig.  194.  Pour  a small 
quantity  of  ether  into  the  flask,  and  of  water  into  the  glass, 
and  place  the  whole  under  the  receiver  of  an  air-pump ; du- 
ring exhaustion,  the  ether  will  boil,  and  a crust  of  ice  will 
gradually  form  upon  the  exterior  of  the  flask.t 

2006.  Ether  is  highly  inflammable,  and  in  con- 
sequence of  its  volatility  it  is  often  kindled  by  the 
mere  approach  of  a burning  body;  a circumstance 
which  renders  it  highly  dangerous  to  decant,  or 
open  vessels  of  ether  near  a candle. § 


Fig.  194. 


The  inflammability  of  ethereal  vapour  may  be  shown  by  passing  a small  quan- 
tity into  a receiver,  furnished  with  a brass  stop-cock  and  pipe,  and  inverted  over 
water  at  a temperature  of  100°.  The  receiver  becomes  filled  with  the  vapour, 
which  ma)i  be  propelled  and  inflamed;  it  burns  with  a bright  bluish-white 
flame. 


2007.  When  ether  is  admitted  to  any  gaseous  body  it  increases 
its  bulk.  Oxygen  thus  expanded,  produces  a highly  inflammable 
mixture ; if  the  quantity  of  oxygen  be  large  and  of  ether  small,  the 
mixture  is  highly  explosive,  and  produces  water  and  carbonic  acid. 

Into  a strong  two  ounce  phial,  filled  with  oxygen  gas,  and  wrapped  round  with 
a cloth,  let  fall  a drop  of  ether.  On  applying  the  flame  of  a candle,  a violent 
detonation  will  ensue. 

2008.  The  vapour  of  ether  also  explodes  with  chlorine,  as  is 
shown  by  the  following  experiment. 

* For  table  of  sp.  gr.  see  Henry’s  Chem.  ii.  333.  + 2.5S22,  T.  and  L. 

t After  using  ether,  air  should  be  drawn  through  the  pump  many  times  to  get  rid  of 

the  ether,  as  it  injures  the  valves. 

§ In  spirit  warehouses  or  druggists’  laboratories  where  ether  is  distilled  the  safety 
lamp  (Fig.  174)  may  be  advantageously  used. 


Chloride  of  Ethal.  451 

Fill  a bottle  of  the  capacity  of  three  or  four  pints,  with  chlorine  gas,  taking  care  Sect.  I. 
to  expel  the  water  as  completely  as  possible.  Then  throw  into  it  about  a drachm  ^ 
or  a drachm  and  a half  of  good  ether,  covering  its  mouth  immediately  with  a piece 
of  light  wood  or  paper.  In  a few  seconds  white  vapour  will  be  seen  moving 
circularly  in  the  bottle,  and  this  will  soon  be  followed  by  an  explosion,  accom- 
panied with  flame.  At  the  same  time  a considerable  quantity  of  carbon  will  be 
deposited. 

When  a small  quantity  of  ether  is  poured  into  a large  jar  of  warm  chlorine,  it 
occasionally  happens  that  a considerable  explosion  ensues. 

2009.  Ether  freezes  at  — 46°.  When  exposed  to  light  in  a vessel 
partially  filled,  and  which  is  frequently  opened,  it  gradually  absorbs 
oxygen,  and  a portion  of  acetic  acid  is  generated. 

2010.  Ether  dissolves  the  resins,  several  of  the  fixed  oils,  and  Dissolves 
nearly  all  the  volatile  oils  ; it  also  dissolves  a portion  of  sulphur,  and  resins,  &c. 
of  phosphorus;  the  latter  solution  is  beautifully  luminous  when 
poured  upon  warm  water  in  a dark  room.  The  fixed  alkalies  are 

not  soluble  in  ether,  but  it  combines  with  ammonia. 

It  dissolves  the  oxides  of  gold  and  platinum,  and  these  solutions  on 

have  been  employed  for  coating  steel  with  those  metals,  with  a view  gold  and 
to  ornament  and  as  a defence  from  rust.^  platinum. 

2011.  When  a coil  of  platinum  wire  is  heated  to  redness,  and 
then  suspended  above  the  surface  of  ether  contained  in  an  open  ves- 
sel (Fig.  53),  the  wire  instantly  begins  to  glow,  and  continues  in 
that  state  until  all  the  ether  is  consumed.  During  this  slow  com- 
bustion, pungent  acrid  fumes  are  emitted,  which,  if*  received  in  a 
separate  vessel,  condense  into  a colourless  liquid  possessed  of  acid 
properties,  owing  to  the  formation  of  acetic  acid. 

2012.  It  has  been  already  stated  (1567)  that  sulphuric  ether  con-  Base  of 
sists  of  C4H5O,  and  that  it  possesses  the  characters  of  a base,  being  ether- 
capable  of  neutralizing  acids,  oxygen,  chlorine,  bromine,  iodine,  and 
fluorine.  These  new  compounds  are  at  present  very  inaccurately 
termed  ethers.  The  base  of  ether  is  C4H5  to  which  Liebig- has  given 

the  name  of  ethyl. t Common  ether  is  an  oxide  of  ethyl,  t 

2013.  In  preparing  ether  the  ebullition  is  continued  till  white  va-  Sweet  oil 
pours  appear,  and  the  smell  of  sulphurous  acid  is  perceived,  and  by  ol  wme- 
continuing  the  heat  a yellowish  liquid  comes  over  which  has  been 
called  the  sioeet  oil  of  wineX 

2014.  Chloride  of  Ethyl— Hydrochloric  Ether.  C4H5C1.  This  chloride  of 
compound  is  generated  by  the  action  of  hydrochloric  acid  on  alcohol,  ethyl, 
and  maybe  prepared  by  several  processes: — by  distilling  alcohol 
previously  saturated  with  hydrochloric  acid  gas,  or  mixed  with  an 


*If  to  a saturated  solution  of  gold  or  platinum,  in  nitro-hydrochloric  acid,  there  be  Ufe  of  ethereal 
added  about  three  parts  by  measure  of  good  sulphuric  ether,  it  soon  takes  up  the  me-  sotu 
tals,  leaving  the  acid  nearly  colourless  below  the  ethereal  solution,  which  is  to  be  c\ 
carefully  decanted  off;  into  this  the  polished  steel  is  for  an  instant  plunged,  and  im- 
mediately afterwards  washed  in  water,  or  in  a weak  alkaline  solution.  Though  the 
coaling  of  platinum  is  the  least  beautiful,  Stodardt,  who  has  made  many  expe- 
riments upon  this  subject,  considers  it  as  the  best  protection  from  rust.  Polished 
brass  may  be  coated  by  the  same  process.  These  surfaces  of  gold  and  platinum, 
though  very  thin,  are  often  a useful  protection ; with  gold  the  experiment  is  particu- 
larly beautiful,  and  well  illustrates  the  astonishing  divisibility  of  the  metal.  The 
ethereal  solution  of  gold  is  not  permanent,  but,  after  a time,  deposits  the  metal  in  the 
form  of  a film,  in  which  crystals  of  gold  are  often  perceptible. 

t From  recent  experiments  LOwig  concludes  that  by  the  action  of  potassium  on 
chloride  of  ethyl,  chloride  and  ethylide  of  potassium  are  formed,  and  that  by  the  ac- 
tion of  water  upon  the  latter,  the  ethyle  is  set  tree.  Lond.  and  Edin.  Phil.  Mag.} 

July,  1839.  t See  T.  Inorg.  Cfiem.  ii.  307,  and  B.  ii.  692. 


452 

Chap.  VI T. 


Properties. 

Sulphuret 
of  ethyl. 

Process. 

Mercaptan. 


Other 

ethers. 


Hydrocyanic 

ether. 

Sulphohydric, 
Chloric  ether. 


Organic  Chemistry — Intermediate  Bodies. 

equal  volume  of  strong  hydrochloric  acid  ; by  heating  a mixture  of 
5 parts  of  alcohol,  5 of  strong  sulphuric  acid,  and  12  of  fused  sea- 
salt  in  fine  powder;  or  by  distilling  alcohol  with  the  chlorides  of 
tin,  bismuth,  antimony,  or  arsenic.  The  products  are  transmitted 
through  tepid  water,  by  which  free  alcohol  and  acid  are  absorbed, 
and  the  pure  hydrochloric  ether  is  then  received  in  a vessel  sur- 
rounded by  ice  or  a freezing  mixture. 

2015.  Hydrochloric  ether  is  a colourless  liquid,  of  a penetrating, 
somewhat  alliaceous,  ethereal  odour,  and  a strong  rather  sweet  taste. 
It  is  so  volatile  that  it  boils  at  about  54°.  When  inflamed,  as  it  issues 
from  a small  aperture,  it  burns  with  an  emerald-green  flame  without 
smoke,  yielding  abundant  vapours  of  hydrochloric  acid. 

2016.  Sulphuret  of  Ethyl , or  Mercaptan.  C4H5S-|-HS.  This 
new  substance  was  discovered  by  Zeise  and  named  mercaptan , on 
account  of  its  energetic  action  on  the  red  oxide  of  mercury.* 

Althionate  of  baryta,  lime,  or  potassa,  was  heated  with  a strong  solution  of 
protosulphuret  of  barium.  There  distilled  over  along  with  the  water  an  ethereal 
liquid,  while  the  althionate  was  changed  into  sulphate. 

2017.  The  ethereal  liquid  was  lighter  than  water,  colourless,  of  a 
penetrating  odour,  resembling  that  of  garlic.  Its  taste  was  sweet ; 
it  inflamed  readily,  giving  out  the  odour  of  sulphurous  acid.  When 
distilled  it  was  divided  into  two  distinct  liquids.  To  the  first 
the  name  of  thialic  ether  was  given,  and  to  the  second  mercaptan. 

2018.  Mercaptan  acts  with  force  upon  potassium,  hydrogen  gas 
being  evolved  and  the  metal  converted  into  a colourless  salt,  very 
soluble  in  water  and  in  alcohol.  These  solutions  give  a yellow  pre- 
cipitate, with  acetate  and  nitrate  of  mercury.! 

There  are  six  bodies  to  which  the  term  ether  has  been  applied,  but 
which  are  not  considered  such  by  Thomson,  by  whom  they  have  been 
constituted  a distinct  class,  having  for  their  base  not  C4HS  but  C4H4 
(the  tetartO’Carbo-hydrogen  of  Thomson),  they  are 

1 Light  oil  of  wine  . . C4  Hi 

2 Chloric  ether  • • . . C4  H4+Cl2t 

3 Bromic  “ . . . . C4  Hi  + Bnj 

4 Iodic  " . . . Ci  Hi  -f-  I2 

5 Acetal  “ . . Ci  H4  + H£0 

C Sulphocyanic 

The  third  set  of  bodies  classed  among  the  ethers,  consists  of  che- 
mical compounds  of  sulphuric  ether  and  an  acid.  Of  these  Thomson 
enumerates  twenty,  for  which  see  Org.  Bodies , 329. 


* Ann.  de  Chim.  et  de  Phys.  lvi.  87. 

t Cyanodidc  of  Ethyl — Hydrocyanic  Ether , C4Ho(C2N),  was  discovered  by  Pelouze, 
and  is  obtained  by  heating  a mixture  of  equal  parts  of  cyanodide  of  potassium  and 
althionate  of  baryta. 

Sulphohydric  Ether,  CiHs(HS)  ? was  formed  by  Lowig  by  the  action  of  oxalic 
ether  and  sulphuret  of  potassium.  It  has  no  action  on  red  oxide  of  mercury,  and  by 
this  character  is  distinguished  from  mercaptan.  See  T*  Org.  Bodies , 328. 

t Chloric  Ether  is  the  name  which  has  been  applied  to  a liquid  obtained  by  distilling 
a gallon  from  a mixture  of  three  pounds  of  chloride  of  lime  and  two  gallons  of  alcohol, 
sp.  gr.  0 844,  and  rectifying  the  product.  This  was  discovered  by  Guthrie  in  the 
United  States  and  Souberain  in  France.  See  Guthrie’s  account  in  Amer.  Jour.  xxi. 
As  this  liquid  does  not  contain  chloric  acid,  Bache  has  proposed  for  it  the  name  of 
chlorine  ether. 

It  is  extremely  volatile,  of  a sweetish  taste,  boiling  at  166°,  and  having  the  sp.  gr. 
of  1.486.  VVhen  diluted  with  water  it  is  employed  as  a diffusible  stimulant. 


Oxalic  Ether . 


453 


2019.  Nitric  ether.  Nitrous  ether ; G4H5O+NO3.  Various  sect.  1. 
processes  are  given  for  obtaining  this  liquid  it  is  produced  by  the  Thomson’s 
action  of  equal  weights  of  nitric  acid  and  alcohol,  the  acid  being  3d  set. 
added  in  small  successive  quantities  to  the  alcohol,  and  the  mixture  Nitric 
cooled  after  each  addition,  to  prevent  the  violent  action  that  would  e 
otherwise  ensue.  It  collects  on  the  surface  of  the  mixture  and  is 
cautiously  withdrawn. 

1.  Fig.  (195)  represents  an  arrangement  proposed  by 
Torrey — a a Woulfe’s  bottle,  b a receiver,  e e glass  fun- 
nels ground  to  the  necks,  and  glass  rods  ground  to  the 
funnels,  the  acid  being  in  one  funnel,  and  the  alcohol 
in  the  other ; by  means  of  the  glass  rods  the  admis- 
sion of  either  is  regulated  at  pleasure. 

2.  Introduce  into  a sufficiently  capacious  retort  equal 
weights  of  alcohol,  (specific  gravity  820)  and  of  nitric 
acid  of  commerce  (specific  gravity  1 30)  and  connect 
it  with  five  Woulfe’s  bottles,  the  first  of  which  is 
empty  and  the  remaining  four  half  filled  with  a satu- 
rated solution  of  salt  in  water.  Apply  a gentle  heat  to  the  retort,  till  the  liquor 
begins  to  effervesce;  then  withdraw  the  fire,  and  the  gaseous  matter  passing 
through  the  bottles,  which  should  be  kept  cold  by  ice,  deposits  the  ether  upon 
the  saline  solution,  from  which  it  is  to  be  decanted,  shaken  with  chalk,  and  re- 
distilled at  a very  gentle  heat.t 

2020.  In  all  experiments  with  nitric  acid  and  alcohol,  great  care  Caution, 
must  be  taken  not  to  mix  a large  quantity  of  acid  with  the  alcohol 

at  once,  as  the  gaseous  products  that  are  immediately  produced  are 
apt  to  throw  out  the  whole  of  the  mixture  with  explosive  violence.! 

Nitrogen,  protoxide  and  binoxide  of  nitrogen,  and  carbonic  acid 
gases  are  disengaged. 

2021.  The  nitrous  agrees  with  sulphuric  ether  in  its  leading  pro- 

perties; but  it  is  still  more  yolatile.  When  recently  distilled  from 
quicklime  by  a gentle  heat,  it  is  quite  neutral ; but  it  soon  becomes 
acid  by  keeping.  It  is  decomposed  by  potassa,  and,  on  evaporation, 
crystals  Qf  the  nitrite  or  hyponitrite  of  that  alkali  are  deposited 
(Mem.  d’Arcueil,  i.)  It  is  soluble  in  48  parts  of  water,  and  in  all 
proportions  in  alcohol ; this  last  solution  is  the  spiritus  cetheris  nitrici , Sweet 
or  sweet  spirit  of  nitre  of  the  Pharmacopoeia.^  sPir^  °f 

2022.  Oxalic  ether.  C4H50-f-C203.  Is  obtained  from  1 part  of™* * * §^ 
alcohol,  1 binoxalate  of  potassa,  and  2 parts  of  sulphuric  acid.  It  ether, 
is  purified  by  boiling  with  pounded  litharge.  It  is  an  oleaginous 
liquid,  boiling  at  263°.  When  a current  of  dry  ammoniacal  gas  is 
passed  over  it  a substance  is  obtained  which  has  been  called  by  Du- 
mas ||  oxamethane .IF 


* Thomson’s  Inorg . Chem.  318- 

t See  description  of  an  apparatus  for  this  process  by  Hare,  in  Am.  Jour.  vol.  ii.  p. 

326  and  xxxiii.  241. 

t Though  a small  quantity  of  acid  may  be  added  to  a large  quantity  of  alcohol 
without  much  action,  a small  quantity  of  alcohol  cannot  be  added  to  a large  quantity 
of  acid  without  violent  action. 

§ Two  lb.  of  nitrate  of  potassa  and  a lb.  and  a half  of  sulphuric  acid  are  mixed  in  a Proceai  for 
glass  retort,  9 and  a half  lbs.  of  alcohol  are  gradually  poured  in  ; it  is  digested  with  a 
gentle  heat  for  two  hours,  the  heat  is  then  raised  and  a gallon  distilled  off;  to  this  I 
pint  of  diluted  alcohol  and  an  ounce  of  carbonate  of  potassa  are  added  and  a gallon 
distilled  off.  U.S.  P- 

|j  Ann.  de.  Chim.  et  de  Phys.  liv.  241,  and  Ann.  de  Pharm.  ix.  129. 

IT  Etheroxalate  of  Potassa.  It  was  shown  by  Leibig  that  oxalic  ether  has  the  pro- 


Prepara- 

tion. 


454 


Chap.  VII. 

iEnanthic 

ether. 


Properties. 


Thomson’s 
4th  set. 


Pyroxylic 

spirit. 


Properties. 


Action  of 

platinum 

sponge. 


Action  of 
sulphuric 
acid. 


Etheroxalate  of 
pola*sa. 


Used  as  a sol- 
vent, &o. 


Organic  Chemistry — Intermediate  Bodies. 

2023.  (Enantkic  ether.  C4H50-j-C14H1302.  It  is  to  this  remarka- 
ble ether  that  the  peculiar  odour  of  wines  is  owing.* *  When  large 
quantities  of  wine  are  distilled  we  obtain,  at  the  end  of  the  process 
a small  quantity  of  an  oily  liquid.  The  same  liquid  is  obtained 
when  the  lees  of  wine  are  distilled ; 

2024.  It  has  a strong  taste,  is  usually  colourless,  and  is  a mix- 
ture of  cenanthic  ether  with  an  excess  of  cenanthic  acid.  The  ether  is 
separated  by  distillation.  It  is  very  liquid,  has  a strong  odour  of 
wine  and  produces  intoxication  when  inspired. t 


2025.  The  fourth  set  of  bodies,  which  have  by  some  been 
classed  among  ethers , are  certain  acidulous  salts,  consisting  of  1 
atom  of  ether  united  to  2 atoms  of  an  acid.  They  are 


1 Heavy  oil  of  wine 

2 Althionic  acid 

3 Phosphovinic  acid 

4 Oxalovinic  acid  - 

5 Tartrovinic  acid  - 

6 Racemovinic  acid 

7 Camphovinic  acid 

2026.  Pyroxylic  spirit. 


C4H5(Hft0l)+S03 
C4H5Q+2(S03)+HO 
C4H50+2(P024) 
C4H50+2(C203)+H0 
C4H50+2(C4H205)+HO 
C4  H50+2(C4  H ,05)+H0 
C4H5  O+atC.cHfiO  5 )+HO 

C.»H30-|-H0=32.  This  name  has  been 


given  to  the  volatile  liquid  which  is  formed  when  wood  is  subjected 
to  heat,  and  which  is  found  in  the  aqueous  liquid  which  comes  over. 
This  is  decanted  off  to  separate  it  from  the  tar,  and  when  again  dis- 
tilled the  pyroxylic  spirit  is  in  the  first  tenth  part  of  the  product.  It 
is  rectified  over  quicklime. 

2027.  Pyroxylic  spirit  is  colourless,  and  has  a peculiar  odour, 
alcoholic  and  aromatic  mixed  with  that  of  acetic  ether.  It  boils  at 
150°,  its  sp.  gr.  is  .798  not  differing  much  from  alcohol. t 

202S.  When  its  vapour  is  mixed  with  air  in  contact  with  plati- 
num sponge,  heat  is  evolved  and  formic  acid  produced.  If  allowed 
to  fall  drop  by  drop  on  the  spongy  platinum,  it  burns  and  carbonic 
acid  is  produced.  Its  vapour  explodes  with  dry  chlorine.  Distilled 
with  chloride  of  calcium  it  gives  rise  to  chloroform. 

2029.  When  a mixture  of  1 part  of  pyroxylic  spirit  and  4 parts 
of  concentrated  sulphuric  acid  is  distilled,  a gas  comes  over,  which 
possesses  the  constitution  of  alcohol  vapour.  The  very  same  thing 
takes  place  in  this  distillation  as  when  we  heat  a mixture  of  alcohol 
and  sulphuric  acid.  One  half  the  water  is  abstracted  relative  to  the 


perty  of  combining  with  bases  like  an  acid,  and  this  salt  is  obtained  when  oxalic 
ether  is  dissolved  in  absolute  alcohol  and  as  much  hydrate  of  potassa  is  added  as 
is  just  sufficient  to  neutralize  half  the  oxalic  acid.  Lehrbuch  der  chim.  2 Aufl. 
i.  644. 

* Ann.  dc  Chim.  et  de  Phys.  lxiii.  113. 

+ For  the  other  ethers  of  this  division  see  T.  Org.  Bodies , 333. 

t Pyroxylic  spirit  is  extensively  used  by  hat  makers,  for  the  purpose  of  dissolving 
shell  lac  and  mastic  to  stiffen  hats  and  render  them  water  proof.  According  to  Scan- 
lan  a fluid  of  higher  sp.  gr.  and  lower  boiling  point  is  oblained  by  distillation  by  sa- 
turating the  purified  acid  with  slacked  lime,  and  subsequent  distillation  as  longas  the 
product  is  of  less  sp.  gr.  than  water.  This  product  is  rectified  in  a still,  consisting  of 
a boiler  and  rectifier  of  copper  of  peculiar  construction  placed  in  a bath  of  wrater,  and 
kept  at  such  a temperature  as  will  condense  water,  but  retain  the  more  volatile  pro- 
ducts in  the  slate  of  vapour  till  they  pass  the  last  part  of  the  apparatus  where  they  are 
cooled.  See  Rep.  Brit.  Assoc.  1835,  40. 


Colouring  Matters . 455 

other  ingredient,  the  carbohydrogen.* * * § **  When  alcohol  is  used  olefiant  Sect,  r, 
gasf  is  converted  into  ether  ; but  when  pyroxylic  spirit  is  used,  the 
compound  is  C2H30,  or  it  contains  an  atom  of  olefiant  gas  less  than 
ether.l 

2030.  When  pyroxylic  spirit  is  made  to  act  on  the  hydracids,  a Action  on 
set  of  compounds  is  formed  very  analogous  to  the  ethers  which  the  hydracids. 
same  acids  form  with  alcohol.  Dumas  and  Peligot  consider  them 
as  compounds  of  the  hydracid  and  a base  which  they  term  methy- 
lene.§ 


CHAPTER  VIII. 

Section  I.  Colouring  Matters. 

2031.  A great  number  of  vegetable  principles  are  comprised 
under  the  term  colouring  matter,  and  are  extensively  employed  in 
the  processes  of  dyeing  and  calioo-printing.H 

2032.  Some  of  these  are  used  as  chemical  re-agents  and  for  test- 
ing the  presence  of  acids  and  alkalies.  The  infusion  of  red  cabbage 
has  been  already  described  (56  n.) ; the  colouring  matter  of  violets 
may  be  used  for  the  same  purpose. 

2033.  Litmus  is  the  blue  colouring  matter  prepared  from  the  lichen 
rocella  which  grows  in  the  Canary  islands,  and  the  leconora  tartarea  Litmus* 
which  is  collected  in  Norway.  From  the  latter  is  also  prepared 
cudbear?*  the  colour  being  developed  by  the  aid  of  ammonia.  The 
colouring  matter  of  the  leconora  has  been  termed  erythrin , and  that 

of  archil  orcin. 

2034.  Litmus  is  more  easily  affected  by  acids  than  the  colouring  Effect  of. 
matter  of  cabbage,  but  is  not  turned  to  a green  by  alkalies.  If  pre-  acids  and 
viously  reddened  by  acids,  it  may  be  used  for  detecting  alkalies,  the  alkalies, 
original  blue  tint  being  restored. ft 


* Carbo-hydrogen  is  the  name  applied  by  Thomson  to  the  gas  evolved  when  pyroxy- 
lic spirit  is  treated  with  aqua  regia,  it  is  composed  of  1 vol.  of  carbon  vapour  and  1 vol. 
of  hydrogen  gas. 

t Deutocarbohydrogen  of  T. 

t This  is  the  same  thing  in  both  cases  as  abstracting  one  half  of  the  water  which 
the  spirit  contained.  But  in  reality 

Alcohol  is  . . . . C<  H5  O + H O 

While  this  gas  is  . . , C2  H2  H O T.  350. 

§ For  details  see  T.  Orff.  Bodies , 350. 

||  Acetone.  C3H3O.  This  name  is  given  to  what  was  termed  pyro-aceiic  spirit,  and  Acetone 
which  is  obtained  by  heating  several  acetates.  It  is  a transparent,  volatile  and  in-  ce  on®‘ 
flammable  liquid,  entering  into  combination  with  water,  alcohol,  ether  and  some  vola- 
tile oils. 

Mesite  is  a product  of  the  distillation  of  wood  named  from  ysairrjs  a mediator. 

5T  For  a more  particular  description  of  the  various  colouring  matters,  and  of  the  pro- 
cesses followed  for  their  extraction  and  fixation,  constituting  the  art  of  dyeing,  the 
student  must  be  referred  to  Thomson’s  Orffanic  Chemistry , 367.  Ure’s  Diet,  of  Arts 
and  Manyf.  Berthollet  on  Dyeing , and  Thomson  on  Calico-printing  in  Records  of 
General  Science,  Vols.  i.  ii.  iii. 

**  First  called  Cuthhert  from  Dr.Cuthbert  Gordon  who  first  made  it. 

tt  To  prepare  test  papers,  rub  some  good  litmus  with  hot  water  in  a mortar,  pour  . 
the  mixture  into  an  evaporating  basin,  and  add  pure  water  until  the  proportion  is  about  u7tPpapef«n  ° 
half  a pint  for  each  ounce  of  litmus.  Cover  it  up  and  keep  warm  for  an  hour,  then 


456  Colouring  Matters. 

Chap,  vni.  2035.  Turmeric  is  the  root  of  the  curcuma  longa,  a plant  grow- 

Turmeric.  ing  in  the  East  Indies.  It  is  yellow  and  its  colouring  matter  has 
been  called  cur  cumin ; it  is  imparted  to  boiling  alcohol  and  sepa- 
rated by  ether  from  which  it  is  obtained  by  distillation.  It  is  changed 
to  brown  by  alkalies  and  some  neutral  salts. 

2036.  Many  colouring  giatters  have  a great  attraction  for  metallic 
oxides,  combining  with  tham  when  they  are  separated  from  solutions 
in  which  both  the  colouring  matter  and  the  oxides  have  been  pre- 
viously dissolved ; thus  when  potassa  is  added  to  a solution  contain- 
ing hydrochlorate  of  tin  and  litmus,  the  potassa  unites  with  the  hy- 
drochloric acid,  litmus  and  oxide  of  tin  falling  down  in  combination. 

Lakes.  The  precipitates  thus  obtained  are  called  lakes. 

2037.  On  this  property  are  founded  many  of  the  processes  in 

Dyeing.  dyeing  and  calico-printing.  The  art  of  the  dyer  consists  in  giving 

a uniform  and  permanent  colour  to  cloth.  This  is  sometimes  effect- 
ed merely  by  immersing  the  cloth  in  the  coloured  solution  ; where- 
as in  other  instances  the  affinity  between  the  colour  and  the  fibre 
of  the  cloth  is  so  slight,  that  it  only  receives  a stain  which  is  re- 
moved by  washing  with  water.  In  this  case  some  third  substance 
is  requisite,  which  has  an  affinity  both  for  the  cloth  and  colouring 
matter,  and  which,  by  combining  at  the  same  time  with  each,  may 
cause  the  dye  to  be  permanent.  A substance  of  this  kind  was  for- 

Mordants.  merly  called  a mordant ; but  the  term  basis , introduced  by  Henry  is 
now  more  generally  employed.  The  most  important  bases,  and  indeed 
the  only  ones  in  common  use,  are  alumina,  oxide  of  iron,  and  oxide 
of  tin.  The  two  former  are  exhibited  in  combination  either  with 
the  sulphuric  or  acetic  acid,  and  the  latter  most  commonly  as  the 
chloride. 

Substantive  2038.  Substantive  colouring  matters  include  those  which  have  so 

colours,  strong  an  attraction  for  cloth,  that  they  can  attach  themselves  to  it 
permanently,  and  without  the  action  of  any  other  substance,  as 
indigo. 

Adjective.  Those  which  require  a mordant  are  termed  adjective  colouring 
matters. 

Bleaching.  2039.  Colouring  matters  are  bleached  by  chlorine,  which  is 
usually  employed  in  union  with  lime  (901)  ; sulphurous  and  some 
other  acids  are  also  used  to  remove  colour. 

Red  dyes,  2040.  For  red  dyes , Brazil  wood,  lac,  archil,  madder  and  cochi- 
neal, are  the  principal  colouring  matters  in  common  use.  The  cochi- 
neal, is  procured  from  an  insect,  which  is  believed  to  derive  its 
colouring  matter  from  a particular  vegetable  principle  upon  which  it 
feeds. 


decant  the  clear  liquor,  and  poor  fresh  hot  water  uprn  the  residue.  Cover  up  and  keep- 
warm  as  before,  evaporate.  These  operations  are  to  be  repeated  until  all  the  colour 
is  removed.  The  first  solution  is  to  be  kept  apart  from  the  second  and  third,  which 
may  be  mixed  and  reduced  by  evaporation  until  a piece  of  filtering  paper  dipped  in 
ana  dried  is  of  a blue  colour.  Paper  is  then  to  he  dipped  into  the  solution ; it  should 
he  bibulous  and  not  sized.  The  solution  should  be  poured  into  a dish  and  the  paper 
be  drawn  through  it  piece  by  piece,  be  drained,  and  dried  where  no  acid  fumes  or  those 
of  burning  charcoal  can  have  access  to  it.  As  soon  as  dry  the  paper  should  be  placed 
in  a well  closed  tin  box.  The  tint  ought  to  be  a pure  blue,  and  can  be  judged  of  by 
applying  a drop  of  very  weak  acid  which  should  produce  a vivid  red.  Turmeric  pa- 
per is  prepared  in  a similar  manner.  See  Faraday’s  Chem.  Manip.  272. 


457 


Indigo — Cerulin . 

2041.  Yellow  dyes  are  procured  principally  from  saffron,  hiccory,  Sect. J- 

quercitron  bark,  turmeric,  fustic  and  annatto.  Yellow, 

2042.  Black  dyes  are  made  with  the  same  materials  as  writing  Black, 
ink,  logwood  and  madder  are  also  employed  with  oxide  of  iron. 

2043.  Blue  dyes  are  commonly  prepared  with  Prussian  blue  or  Blue, 
indigo.  Three  different  colouring  principles  have  been  detected  in 
indigo,  indigo  blue , indigo  red  and  indigo  brown . It  is  obtained 
from  an  American  and  Asiatic  plant  the  Indigofcra,  and  the  Ne- 
rium  tinctorium  ; an  inferior  sort  is  prepared  from  the  Isatis  tinctoria 

or  wood,  a native  of  Europe. 

2044.  Indigo  C16H5N02  as  it  occurs  in  commerce,  is  far  from  being  Indigo, 
pure,  more  than  half  its  weight  consisting  of  matter  destitute  of  a blue 
colour  and  incapable  of  being  used  as  a dye  stuff.  Part  of  these 
impurities  may  be  dissolved  by  water,  part  by  alcohol,  and  part  by 
dilute  acids  and  by  alkaline  leys. 

2045.  The  best  way  of  obtaining  pure  indigo,  is  from  the  calico-printers’  Obtained 
vat,  in  which  the  indigo  has  been  deprived  of  its  blue  colour  by  sulphate  of  iron  pure, 
and  is  held  in  solution  by  means  of  lime  water.  The  colour  of  this  solution  is  yel- 
low. If  a quantity  of  it  be  put  into  an  open  vessel  it  absorbs  oxygen  from  the 
atmosphere  and  the  indigo  precipitates  of  a blue  colour.  If  the  precipitate  be 
digested  in  hydro-chloric  acid,  washed  and  dried,  it  is  pure  indigo. 

2046.  Indigo  sublimes  in  long  flat  needles  at  about  550°,  its  va-  Sublimed 
pour  is  transparent  and  reddish  violet.  It  melts  and  is  decomposed  indigo- 
at nearly  the  same  temperature.  The  sp.  gr.  of  sublimed  indigo 

is  1.35. 

2047.  It  is  insoluble  in  water,  but  soluble  in  sulphuric  acid,  the  Solubility, 
indigo  being  changed  into  what  has  been  termed  cerulin.*  It  is  de-  &c- 
composed  by  nitric  acid,  with  the  formation  of  indigotic  and  carba- 

zotic  acids. 

2048.  When  treated  with  something  capable  of  abstracting  oxy- Action  of 
gen,  it  assumes  a white  or  yellowish-white  colour,  and  becomes  solu-  substance^ 
ble  in  the  different  bases.  This  white  substance  has  been  called  by 

Liebig  indigo  gen,  it  does  not  alter  by  exposure  to  dry  air,  but  when  indigogen. 
placed  under  water  assumes  a deep-blue  colour  and  acquires  a cop- 
pery tint  when  dried.  It  dissolves  in  alkalies,  but  does  not  neu- 
tralize them.  It  is  soluble  in  alcohol,  but  insoluble  in  acids  and 
water. 

Fill  one  leg  of  a syphon  with  a solution  of  indigogen  in  lime  water,  and  the  Exp. 
other  leg  with  hydrochloric  acid,  the  indigogen  will  separate  in  white  flocks. 

Substitute  nitric  acid  for  hydrochloric,  the  precipitate  will  become  blue  and  gra- 
dually disappear. 

Make  a solution  of  indigogen  in  lime  water,  pass  oxygen  gas  into  it,  it  will  be  EXp. 
absorbed  and  indigo  be  reproduced  and  precipitated. 

2049.  Cerulin  is  precipitated  from  the  solution  in  sulphuric  acid  cerulin. 
by  any  salt  of  potassa  formin g ceruleo-sulyhate  of  potassa,  of  so  deep 

a blue  colour  that  when  moist  it  appears  black.  Water  in  a wine 
glass  containing  °f  its  weight  of  it  is  distinctly  blue.t 

2050.  According  to  Crum  if  the  action  of  sulphuric  acid  on  indi- phenicin 
go  be  stopped  at  a certain  point  a new  substance  is  formed  possess- 

* Saxon  blue • 

+ According  to  Berzelius  when  indigo  is  dissolved  in  sulphuric  acid,  two  new  acids 
are  formed  hypo-sulpho-indigotic  and  sulpho -indigotic. 

58 


458 


Chap  fX. 


Uses  of  in- 
digo. 


Different 
tints  produ- 
ced. 


Anotta. 


Saffron. 

Chlor- 

ophyllite. 

Chromule. 


Oils,  their 
characters, 


Zunthin. 

Carthamin. 


Organic  Chemistry — Oleaginous  Substances. 

in g rather  singular  properties.  It  is  formed  at  the  instant  indigo 
changes  from  yellow  to  blue;  Crum  has  called  this  phenicin* * * § 

2051.  Indigo  is  used  for  dyeing  woollen,  silk,  linen  and  cotton 
blue.  To  enable  it  to  combine  with  the  cloth,  it  must  be  in  a state 
of  solution  and  this  state  is  induced  in  two  ways.  I.  The  indigo  is 
deprived  of  its  oxygen,  and  reduced  to  the  state  of  indigogen  ; this 
combines  with  alkalies  and  forms  a compound  soluble  in  water. 
2.  The  indigo  is  dissolved  in  sulphuric  acid,  as  in  dyeing  Saxon 
blue.!  T- 

2052.  By  combining  red,  yellow,  blue  or  black  colouring  matters, 
all  other  tints  may  be  produced,  and  by  varying  the  strength  of 
the  colouring  matter,  or  the  strength  of  the  mordant,  different  shades 
of  the  same  colour  may  be  had.t 

2053.  Anotta  or  Rocou  is  a name  given  to  the  pulp  of  the  seeds 
of  the  bixa  orellena  a South  American  shrub.  It  dissolves  in  small 
quantity  in  water,  better  in  alcohol,  and  the  solution  is  orange  yel- 
low. It  is  often  adulterated  with  powder  of  bricks,  &c.  ; the  fraud  is 
detected  by  exposing  anotta,  previously  dried  at  212°,  to  a red  heat 
till  it  is  quite  burnt.  If  the  anotta  be  pure  the  residual  matter  will 
not  exceed  13  per  cent.  ; all  over  that  is  adulteration. § 

2054.  Saffron  consists  of  the  dried  stigmas  of  the  crocus  sativus. 
The  colouring  matter  is  termed  polychroite  on  account  of  the  nume- 
rous colours  which  it  is  capable  of  assuming.  It  is  obtained  from 
the  watery  infusion  of  saffron  by  evaporation,  digestion  of  the  resi- 
duum in  alcohol  and  evaporation. 

2055.  Chlorophyllite&v  Chr'omulite  is  the  term  applied  to  the  green 
colouring  matter  of  vegetables  ; in  the  autumn  it  is  reddened  by  the 
production  of  acid. 

2056.  Chromule  is  the  name  given  to  the  various  coloured  prin- 
ciples obtained  from  the  leaves  and  flowers  of  plants. 


CHAPTER  IX. 

Section  I.  Oleaginous  Substances. 

2057.  Oils  are  characterized  by  a peculiar  unctuous  feel,  by  in- 
flammability and  by  insolubility  in  water.  They  have  been  divided 
into  fixed  and  volatile  oils,  the  former  being  comparatively  fixed  in 
the  fire  and  giving  a permanent  greasy  stain  to  paper,  while  the  lat- 
ter, owing  to  their  volatility  produce  a stain  which  disappears  by 
gentle  heat. 


* Ann.  Philos.  2d  series,  v.  95.  Berzelius  calls  it  the  purple  of  indigo.  TraiUde 
Chim.  vi.  98. 

t For  details  see  T.  Org.  Bodies , 381. 

t Zanthin  is  obtained  from  madder  and  is  yellow ; the  other  coloupng  principle  of 
this  root  is  alizarin  and  is  red. 

Carthamin  is  the  red  colouring  matter  of  safflower.  From  this  rouge  is  prepared, 
the  carthamin  being  ground  with  talc. 

Hoematin  is  the  colouring  matter  of  logwood  5 Brezilin  of  Brazil  wood ; Santalin 
of  Red  sanders. 

§ Jour,  de  Pharm.  xxii.  101. 


H*matin. 


Fixed  Oils . 459 

2058.  There  seems  little  reason  to  doubt  that  the  fixed  oils  con-  Sect,  i. 
stitute,  in  reality,  salts,  or  rather  each  oil  is  a mixture  of  two  or 

more  salts,  if  the  term  salt  can  be  applied  to  the  compounds  of  the 
oily  acids  with  glycerin,  which  acts  the  part  of  a base.  T,  427. 

2059.  The  fixed  oils  are  usually  contained  in  the  seeds  of  plants,  Fixed, 
as  for  example  in  the  almond,  linseed,  rape-seed,  and  poppy-seed  ; 

but  olive  oil  is  extracted  from  the  pulp  which  surrounds  the  stone.  Obtained, 
They  are  procured  by  bruising  the  seed,  and  subjecting  the  pulpy 
matter  to  pressure  in  hempen  bags,  a gentle  heat  being  generally 
employed  at  the  same  time  to  render  the  oil  more  limpid. 

2060.  Fixed  oils  are  nearly  inodorous,  have  little  taste,  and  are  Properties, 
lighter  than  water,  their  density  in  general  varying  from  0.9  to  0.96. 

Some,  such  as  cocoa-nut  and  palm-oil,  are  fixed  at  50°  or  60  ; but 
most  of  them  are  fluid  at  common  temperatures,  and  they  all  be- 
come limpid  in  becoming  warm.  They  are  commonly  of  a yellow 
colour,  but  may  be  rendered  nearly  or  quite  colourless  by  the  action 
of  animal  charcoal.  At  or  near  600°  they  begin  to  boil,  but 
suffer  partial  decomposition  at  the  same  time,  an  inflammable  vapour 
being  disengaged  even  below  500°.  When  heated  to  redness  in 
close  vessels,  a large  quantity  of  the  combustible  compounds  of  car- 
bon and  hydrogen  is  formed,  together  with  the  other  products  of 
the  destructive  distillation  of  vegetable  substances ; and  in  the  open 
air  they  burn  with  a clear  white  light,  and  formation  of  water  and 
carbonic  acid.  They  may  hence  be  employed  for  the  purposes  of 
artificial  illumination,  as  well  in  lamps,  as  for  the  manufacture  of 
gas. 

2061.  By  exposure  to  the  air  they  absorb  oxygen,  become  rancid  Effect  of 
and  sometimes  assume  a waxy  consistence.  Some  few,  such  as  lin-  air- 
seed,  and  nut-oil,  and  the  oils  of  the  poppy  and  hemp-seed  become 
covered  with  a pellicle,  and  when  thinly  spread  upon  a surface,  in- 
stead of  remaining  greasy,  become  hard  and  resinous  ; these  are 
termed  drying  oils,  and  their  drying  quality  is  much  improved  by  Dryingoils. 
boiling  them  upon  a small  quantity  of  litharge.* 

2062.  The  absorption  of  oxygen  by  fixed,  and  especially  by  dry-  Spontane- 
ing  oils,  is  under  some  circumstances  so  abundant  and  rapid,  and  °us  com- 
accompanied  with  so  much  heat,  that- light  porous  combustible  mate-  ustl0a‘ 
rials,  such  as  lampblack,  hemp,  or  cotton-wool,  may  be  kindled  by 

it.  Substances  of  this  kind,  moistened  with  linseed-oil,  have  been 
known  to  take  fire  during  the  space  of  24  hours,  a circumstance 
which  has  repeatedly  been  the  cause  of  extensive  fires  in  warehouses 
and  in  cotton  manufactories. 

2063.  Nitric  acid  acts  with  great  energy  on  the  fixed  oils.  In  a Actinn  0f 
small  proportion,  its  chief  effect  is  to  render  them  thicker.  Red  and  nitric  acid, 
smoking  nitric  acid,  when  suddenly  mixed  with  a fixed  oil,  especially 

with  the  addition  of  a little  sulphuric  acid,  occasions  a violent  com- 


* The  drying  oils,  and  especially  nut-oil,  form  the  basis  of  printer's  ink,  the  history  Printers»  ink. 
of  which  will  he  found  in  Lewis’s  Phil.  Commerce  of  the  Arts.  The  oil  is  heated  and 
set  fire  to,  and  after  having  been  suffered  to  burn  for  half  an  hour  is  extinguished,  and 
boiled  till  it  acquires  a due  consistency 3 in  this  state  it  is  called  Varnish,,  and  is 
viscid,  tenacious,  and  easily  miscible  with  fresh  oil,  or  with  oil  of  turpentine,  by 
which  it  is  properly  thinned,  and  afterwards  mixed  with  rosin,  soap,  and  lamp-black. 

See  also  Ure’s  Diet.  Arts  and  Manuf.  1031. 


460 


Organic  Chemistry — Oleaginous  Substances. 


ChaP- IX-  bustion.  Chlorine  gas,  passed  through  them,  thickens  them,  and  ren- 
ders them  tenacious  like  wax. 

Effect  °f  2064.  Fixed  oils  are  converted  into  a peculiar  kind  of  acids*  and 
&c  a 1GS’  glycerin  when  heated  with  the  fixed  alkalies  and  water.  The  acids 
uniting  with  the  alkali  constitute  soap,  the  glycerin  remains  in  solu- 
tion. The  acids  are  the  margaric,  stearic  and  oleic. 

Stearine  2065.  The  researches  of  Chevreul  on  the  nature  of  oils  and  fats 
and  Oleine,  have  shown  that  these  bodies  are  compounds  of  at  least  two  other 
compounds,  one  of  which  is  solid  at  common  temperatures,  while 
the  other  is  fluid.  To  the  former  he  applied  the  name  of  stearine, 
from  areaQ  suet,  and  to  the  latter  elaine  or  oleine , from  elaiov  oil. 
Oleine  is  the  fluid  principle  of  oils,  and  gives  fluidity  to  those  oils 
in  which  it  predominates.  It  requires  a cold  of  20°  for  congelation, 
and  is  prepared  from  oils  by  exposing  them  to  a cold  of  about  25°, 
and  pressing  the  congealed  mass  between  folds  of  bibulous  paper ; 
when  the  oleine  is  absorbed,  and  may  be  separated  by  pressing  the 
paper  under  water.  Oleine  is  well  adapted  for  lubricating  the 
wheels  of  watches  or  other  delicate  machinery,  since  it  does  not 
thicken  or  become  rancid  by  exposure  to  the  air.t 
Croton  oil.  2066.  Croton  oil,  is  obtained  from  the  seeds  of  the  croton  tiglium , 
a tree  growing  in  the  East  Indies.  It  is  yellow,  of  an  acrid  taste, 
soluble  in  alcohol  and  ether.  Its  purgative  qualities  are  owing  to  a 
portion  of  crotonic  acid  dissolved  in  the  oil.  A single  drop  generally 
acts  as  a purgative. 

Olive  oil.  2067.  Olive  oil  is  expressed  from  the  pericarpium  of  the  fruit  of 
the  olea  europea,  or  common  olive.  Its  sp.  gr.  at  77°  is  .9109,  it 
congeals  at  36°  depositing  little  spheres  of  stearin. 

Action  of  2068.  By  the  action  of  hyponitrous  acid  on  olive  oil  a solid  is 
hyponitrous  formed  which  has  been  called  elaidin  ; it  is  saponified  by  potassa  or 
soda,  glycerin  being  evolved  and  a fatty  acid  which  combines  with 
the  alkali  and  forms  soap.  The  acid  has  been  called  the  elaidic 
acid. 

Palm  oil.  2069.  Palm  oil  is  one  of  the  solid  oils  and  is  extracted  from  the 
cocos  butyracece  ; it  is  yellow  and  has  the  consistence  of  lard.  It  is 
said  to  be  composed  of  stearine  31,  elaine  69.  It  is  used  in  the 
manufacture  of  yellow  soap. 

Cocoa  oil.  2070.  Cocoa  nut  oil  is  white  and  hard,  and  contains  both  elaine 
and  stearin.  It  is  used  as  a substitute  for  tallow.  The  stearin  is 
used  as  a substitute  for  wax  in  the  manufacture  of  candles. 

Wax.  2071.  Wax  differs  from  the  solid  vegetable  oils  in  its  consistence 

and  in  the  way  in  which  it  combines  with  alkalies  ; but  it  resem- 
bles them  so  much  that  an  accurate  line  of  separation  cannot  be 
drawn. 

Beeswax.  2072.  Bee's  wax,  though  an  animal  production,  agrees  so  closely 
with  wax  from  plants,  that  it  would  be  improper  to  separate  them. 
It  is  an  exudation  from  the  rings  in  the  abdomen  of  bees. 


* See  Oily  Acids. 

t The  watchmakers  purify  olive  oil,  by  plaeing  it  in  a phial  along  with  a plate  of 
lead  ; after  being  corked  it  is  exposed  in  a window  to  the  direct  rays  of  the  sun.  A 
cheesy  matter  separates,  the  oil  loses  its  colour  and  becomes  limpid.  The  clear  oil 
is  poured  off  and  kept  for  use. 


Volatile  Oils . 


461 


2073.  Yellow  wax  is  purified  by  fusion  in  water  and  casting  into  Sect,  n. 
thin  ribbons  which  are  exposed  to  light  and  moisture  by  which  it  is  Purified, 
bleached.  When  pure  it  has  no  taste  or  smell,  unbleached  wax 

fuses  at  142°,  if  bleached,  at  155°  ; the  sp.  gr.  of  the  former  is 
about  .9600,  of  the  latter  .8203.  It  is  insoluble  in  water,  but  soluble 
in  boiling  alcohol. 

2074.  Bee’s  wax  has  been  stated  to  contain  two  distinct  kinds  of  Cerin  and 
wax,  called  cerin  and  myricin M Cerin  is  soluble  in  fixed  and  vola-  mYricln- 
tile  oils,  insoluble  in  water,  cold  alcohol  and  ether,  and  of  the  con- 
sistence of  wax.  It  unites  with  caustic  alkalies  and  forms  a soap. 

It  fuses  at  143£°. 

2075.  Myricin  fuses  at  149°,  at  common  temperatures  is  insoluble 
in  alcohol.  It  cannot  be  converted  into  soap  by  caustic  potassa. 
According  to  .Hess  100  parts  of  wax  are  composed  of 

Hydrogen,  - 12.95 

Carbon  ------  79.77 

Oxygen  ------  7.33* 

3076.  Myrtle  wax  is  obtained  from  the  myrica  cerifera , a shrub  M tje 
that  is  common  in  the  United  States.  The  wax  is  separated  from  Wax. 
the  berries  by  means  of  hot  water.! 

2077.  Galactin , or  cow-tree  wax  exists  in  the  milk  of  the  cow  tree 
Galactoderdron  utile , a large  tree  resembling  the  fig,  which  grows 
in  South  America. 


Section  II.  Volatile  Oils. 

2078.  The  volatile  oils  may  be  divided  into  three  sets  ; 1.  Those  volatile 
that  contain  only  carbon  and  hydrogen  ; they  are  lighter  than  water,  oils, 
and  seem  to  have  the  property  of  combining  in  definite  proportions 

with  acids.  Hence  they  are  probably  bases  or  analogous  to  bases. 

2.  Those  that  contain  carbon,  hydrogen  and  oxygen.  They  are  pro- 
bably as  heavy,  or  heavier  than  water,  and  seem  to  have  the  pro- 
perty of  combining  in  definite  proportions  with  bases,  and  are,  there- 
fore, analogous  to  acids.  3.  Vesicating  oils.  They  contain  sulphur, 
and  probably  also  nitrogen. 

2079.  These  oils  are  generally  obtained  by  distilling  the 
plants  which  afford  them  with  water  in  common  stills ; the 
water  and  oil  pass  over  together,  and  are  collected  in  the 
Italian  recipient  shown  in  Fig.  196,  in  which  the  water  ha- 
ving reached  the  level  a b , runs  off  by  the  pipe  c,  and  the 
oil  being  generally  lighter  than  water,  floats  upon  its  surface 
in  the  space  d.  The  whole  contents  of  the  recipient  are 
then  poured  into  a funnel,  the  tube  of  which  is  closed  with 
the  finger,  and  when  the  oil  has  collected  upon  the  surface, 
the  water  is  suffered  to  run  from  it,  and  the  oil  transferred 
into  a bottle.  The  distilled  water  being  saturated  with  the 
oil,  should  be  retained  for  a repetition  of  the  distillation. 

The  produce  of  oil  is  sometimes  increased,  by  adding  salt 
to  the  water  in  the  still,  so  as  to  elevate  its  boiling  point  a few  degrees. 


* According  to  late  experiments  of  Hess  bee’s  wax  when  pure,  is  always  of  the 
same  constitution,  but  by  oxidation  is  converted  into  an  acid. 

t According  to  Ettling’s  analysis,  cerin,  myricin  and  cerain  are  isomeric  bodies,  and 
composed  of  C18H19O. 
t See  Dana's  analysis,  Amec.  Jour.  1.  294. 


Fig.  196. 


How  ob- 
tained. 


462 


Chap  IX. 


Properties. 


Adultera- 

tion. 


Exp. 


Oil  of  tur- 
pentine. 


Action  of 
hydrochlo- 
ric acid. 


Boiling 

point. 


Organic  Chemistry — Oleaginous  Substances. 

Some  of  the  volatile  oils  are  obtained  by  expression,  such  as  those 
of  lemon , orange , and  bergamot , which  are  contained  in  distinct  ve- 
sicles in  the  rind  of  those  fruits. 

2080.  The  volatile  oils  vary  considerably  in  specific  gravity,  as 
will  be  seen  by  referring  to  the  Tables. 

The  volatile  oils  have  a penetrating  odour  and  taste,  and  are  gene- 
rally of  a yellowish  colour ; they  are  for  the  most  part  very  soluble 
in  alcohol,  and  very  sparingly  soluble  in  water  ; these  solutions  con- 
stitute perfumed  essences  and  distilled  waters.  The  latter  are  princi- 
pally employed  in  pharmacy,  and  the  former  as  perfumes. 

When  pure  they  pass  into  vapour  at  a temperature  somewhat 
below  that  of  212°,  when  distilled  with  water,  they  pass  over  at  its 
boiling  point.  They  are  inflammable,  and  water  and  carbonic  acid 
are  the  results  of  their  perfect  combustion.  As  many.of  these  oils 
bear  a very  high  price,  they  are  not  unfrequently  adulterated  with 
alcohol  and  fixed  oils.  The  former  addition  is  rendered  evident  by 
the  action  of  water ; the  latter  by  the  greasy  spot  which  they  leave 
on  paper,  and  which  does  not  evaporate  when  gently  heated. 

2081.  Nitric  and  sulphuric  acids  rapidly  decompose  the  volatile 
oils. 

A mixture  of  four  parts  of  nitric,  and  one  of  sulphuric  acid,  poured  into  a 
small  quantity  of  oil  of  turpentine,  produces  instant  inflammation. 

2082.  The  relative  quantity  of  essential  oils,  furnished  from  dif- 
ferent materials,  is  liable  to  much  variation ; the  products  of  1 cwt. 
of  the  different  vegetable  substances  are  given  below.* 

2083.  Oil  of  turpentine  is  obtained  from  turpentine,  a viscid, 

transparent,  semifluid  substance,  which  exudes  from  various  species 
of  the  genus  pinus.  Common  turpentine  of  the  shops  flows  by  inci- 
sion from  the  pinus  abies  and  pinus  sylvestris.  To  obtain  the  vola- 
tile oil,  called  oil  of  turpentine,  the  turpentine  is  mixed  with  water 
and  distilled.  The  oil  comes  over  with  the  water,  and  the  residue 
is  common  rosin.  • 

2084.  Oil  of  turpentine  absorbs  a large  quantity  of  hydrochloric 
acid,  and  forms  a crystallizable  substance  resembling  camphor. 
From  the  analysis  of  artificial  camphor  it  is  probable  that  pure  oil  of 
turpentine  is  C20H16. 

20S5.  Oil  of  turpentine  begins  to  boil  at  313° ; if  the  ebullition  is 
continued  the  temperature  rises  to  350°,  or  even  higher,  showing  the 
presence  of  more  than  one  volatile  oil.  The  sp.  gr.  of  its  vapour  at 
313°  is  4.83  air  = 1. 


* Juniper  berries  (common) 

Ounces. 
4 to  5 

Dilto  (fine  Italian) 

. 

. 

7 to  8 

Aniseed  (common) 

. 32  to  36 

Ditto  (finest) 

. 

. 

36  to  38 

Caraways 

. from 

tbs. 

3 

oz.  lbs.  oz. 
12  to  4 12 

Dill  seed 

from 

2 

to  2 6 

Cloves 

from  18 

to  20 

Pimento 

from 

2 

to  3 4 

Fennel-seed 

. 2 

Leaves  of  the  Juniperus  Sabina 

14 

Resins ... 


463 


2086.  It  takes  fire  in  chlorine,  giving  out  much  smoke.  It  dis-  Sect.n._ 
solves  iodine.^ 

20S7.  Camphors.  The  term  camphor  has  been  applied  by  apo-  Camphors, 
thecaries  to  various  solid  bodies,  which  occasionally  appear  in  vola- 
tile oils.  They  are  distinguished  by  their  great  volatility,  a strong 
and  peculiar  smell,  by  melting  when  heated,  and  burning  brilliantly 
when  held  to  a lighted  candle. 

2088.  Common  Camphor.  C^HgOi.  In  its  ordinary  state  it  is  Common 
white,  semi-transparent,  and  concrete.  Its  specific  gravity  .9887.  It  camph°r- 
fuses  at  about  300°,  in  close  vessels.  It  dissolves  in  the  fixed  and 
volatile  oils  and  in  alcohol.  It  is  scarcely  acted  upon  by  the  alka- 
lies ; some  of  the  acids  dissolve,  others  decompose  it. 

The  camphor  of  commerce  is  obtained  from  the  Laurus  Camphora , 
and  comes  chiefly  from  Japan.  It  is  originally  separated  by  distil- 
lation, and  subsequently  purified  in  a subliming  vessel  somewhat  of 
the  shape  of  a turnip,  from  which  the  cakes  of  camphor  derive  their 
form.  When  slowly  sublimed  it  crystallizes  in  octohedrons  or  in  six- 
sided  pyramids. 

2089.  The  analysis  of  camphor  by  Dumas  gave  carbon  78.02,  hy-  Composi- 

drogen  10.39,  oxygen  11.59.  tion. 

2090.  Camphrone  was  discovered  in  1835  by  Fremy,  bypassing  Camph- 
fragments  of  camphor  into  a porcelain  tube,  heated  to  redness,  and  rone* 
containing  lime.  It  is  a slightly  coloured  liquid,  having  the  odour 

of  camphor.  It  boils  at  167°. 

2091.  Dumas  distinguishes  by  the  name  camphogene , what  he  Campho- 
considers  as  the  basis  of  camphor.  It  is  a volatile  oil  composed  of  10  gene’ 
atoms  carbon  and  8 atoms  hydrogen.  It  may  be  extracted  pure  from 
artificial  camphor.  Camphor  consists  of  an  integrant  particle  of 
camphogene  and  an  atom  of  oxygen. t 

2092.  Resins.  Resins  are  the  inspissated  juices  of  plants,  and  Resins, 
commonly  occur  either  pure  or  in  combination  with  an  essential  oil. 

They  are  solid  at  common  temperatures,  brittle,  inodorous,  and  insi- 
pid. They  are  non-conductors  of  electricity’',  and  when  rubbed  be- 
come negatively  electric.  They  are  generally  of  a yellow  colour, 

and  semi-transparent. 

2093.  Resins  are  fused  by  the  application  of  heat,  and  by  a still 
higher  temperature  are  decomposed.  In  close  vessels  they  yield  em- 
pyreumatic  oil,  and  a large  quantity  of  carburetted  hydrogen,  a 
small  residue  of  charcoal  remaining.  In  the  open  air  they  burn 
with  a yellow  flame  and  much  smoke,  being  resolved  into  carbonic 
acid  and  water. 

2094.  Resins  are  dissolved  by  alcohol,  ether,  and  the  essential  Solvents  of. 
oils,  and  the  alcoholic  and  ethereal  solutions  are  precipitated  by  wa- 
ter, a fluid  in  which  they  are  quite  insoluble.  Their  best  solvent  is 

pure  potassa  and  soda,  and  they  are  also  soluble  in  the  alkaline 


* The  volatile  oils  are  very  numerous ; many  of  them  have  been  described  by  Thom- 
son, but  there  are  many  not  yet  described.  Raybaut  of  Paris  has  given  a table  of  no 
fewer  than  207  volatile  oils  prepared  by  himself,  with  the  names  of  the  plants  from 
which  they  were  obtained,  and  the  quantity  from  a given  weight  of  the  plant,  in  the 
Jour . de  Pharm.  xx.  444.  See  T.  Organic  Bodies,  459. 

t For  description  of  camphors  from  oil  of  peppermint  and  other  essential  oils,  see 
T.  Org.  Bodies , 493. 


464 


Chap.  IX 


Uses. 


Tar  and 
pitch. 


Balsams. 


Venice  tur- 
pentine. 


Copaiva. 


Properties. 


Organic  Chemistry — Balsams . 

carbonates  by  the  aid  of  heat.  The  product  is  in  each  case  a soapy 
compound,  which  is  decomposed  by  an  acid. 

Concentrated  sulphuric  acid  dissolves  resins  ; but  the  acid  and  the 
resin  mutually  decompose  each  other,  with  disengagement  of  sulphu- 
rous acid,  and  deposition  of  charcoal.  Nitric  acid  acts  upon  them 
with  violence. 

2095.  The  uses  of  resin  are  various.  Melted  with  wax  and  oil, 
resins  constitute  ointments  and  plasters.  Combined  with  oil  or 
alcohol,  they  form  different  kinds  of  oil  and  spirit  varnish.  Sealing 
wax  is  composed  of  lac,  Venice  turpentine,  and  common  resin.  The 
composition  is  coloured  black  by  means  of  lampblack,  or  red  by  cin- 
nabar or  red  lead.  Lampblack  is  the  soot  of  imperfectly  burned 
resin. 

Of  the  different  resins  the  most  important  are  common  rosin,  copal, 
lac,  sandarach,  mastich,  elemi,  and  dragon’s  blood. 

2096.  When  turpentine  is  extracted  from  the  wood  of  the  fir-tree 
by  heat,  partial  decomposition  ensues,  and  a dark  substance,  consist- 
ing of  resin,  empyreumatic  oil,  and  acetic  acid  is  the  product.  This 
constitutes  tar ; and  when  inspissated  by  boiling,  it  forms  pitch. 
Common  resin  fuses  at  276°,  is  completely  liquid  at  306°,  and  at 
about  316°,  bubbles  of  gaseous  matter  escape,  giving  rise  to  the  ap- 
pearance of  ebullition.  By  distillation  it  yields  empyreumatic  oils  : 
in  the  first  part  of  the  process  a limpid  oil  passes  over,  which  rises  in 
vapour  at  300°,  and  boils  at  360°  ; but  subsequently  the  product  be- 
comes less  and  less  limpid,  till  towards  the  close  it  is  very  thick. 
This  matter  becomes  limpid  when  heat  is  applied,  and  boils  at  about 
500°  F.  At  a red  heat  resin  is  entirely  decomposed,  yielding  a large 
quantity  of  combustible  gas,  which  has  been  employed  for  the  pur- 
pose of  artificial  illumination. * 

2097.  Balsams.  These  are  semi-fluid  resins  containing  a volatile 
oil,  which  may,  in  general,  be  separated  by  distillation,  leaving  the 
solid  resin.  In  this  division  Thomson  includes  turpentine  in  which 
the  oil  is  united  with  two  resins,  which  Unverdoben  has  distin- 
guished by  the  names  pinic  and  silvic  acids , and  Berzelius  by  the 
terms  resin  alpha  and  resin  beta.  The  oil  varies  from  5 to  25  per 
cent.,  as  do  the  resins  also. 

2098.  Venice  turpentine  is  extracted  from  the  pinus  larix , or  com- 
mon  larch.  It  is  limpid,  of  a light  yellow  colour,  and  of  the  consis- 
tence of  honey.  It  contains  from  IS  to  25  per  cent,  of  oil  of  turpen- 
tine, what  remains  after  distillation  is  colophan  or  common  rosin.  It 
dissolves  in  alcohol. t 

2099.  Copaiva  is  obtained  from  the  copaifera  officinalis  and  coria- 
cea;  it  exudes  from  incisions  made  in  the  trunk  of  the  tree.  It  is 
transparent,  yellow,  of  an  agreeable  smell  and  pungent  taste.  Its  sp. 
gr.  is  0.950.  It  yields  a volatile  oil  by  distillation. 

2100.  It  is  insoluble  in  water,  but  imparts  to  it  its  peculiar  taste 


* In  the  arrangement  of  the  apparatus  for  this  purpose,  the  rosin  liquefied  by  heat  is 
allowed  to  pass  into  the  retort  containing  coal  or  colce.  It  has  not  been  found  econo- 
mical in  England.  See  Ure’s  Diet.  Arts  and  Manuf.  1076. 
t Slrasburg  turpentine  is  extracted  from  the pinus  picea. 

Canada  balsam  is  obtained  from  the  pinus  canadensis  and  balsamea  and  the  tur- 
pentine of  Cyprus  and  Chio  from  the  pistacea  lerebinthus. 


Copal.  465 

and  smell.  It  dissolves  in  all  proportions  in  absolute  alcohol ; alco-  Sect,  n. 
hoi  of  sp.  gr.  0.848  dissolves  only  the  9th  or  10th  of  its  weight.  It 
dissolves  in  ether  and  fixed  and  volatile  oils.* * * §  It  combines  with  sa- 
lifiable bases.  It  has  a remarkable  affinity  for  magnesia,  1 part  of 
magnesia  dissolving  in  30  of  balsam  into  a transparent  liquid. 

3101.  It  is  sometimes  adulterated  with  fixed  oils  ; which  can  be  Adultera- 
detected  by  alcohol  dissolving  the  balsam  but  leaving  the  oil.  Cas-  detect' 
tor  oil  is  however  soluble  in  alcohol,  but  it  may  be  detected  by  agi- 
tation with  ammonia,  sp.  gr.  .965,  in  a glass  tube  ; the  solution  is 
transparent  if  the  balsam  be  pure,  but  milky  if  it  contains  castor  oil. 

2102.  Balsam  of  Peru  is  obtained  from  the  myroxylon  peruiferum  Ba]samof 
of  South  America.  Two  varieties  occur  in  commerce,  one  obtained  peru 
by  incisions  in  the  tree,  having  a slight  tint  of  yellow;  the  other  by 
boiling  the  branches  and  bark  of  the  tree  in  water. 

According  to  the  analysis  of  Stoltze  balsam  of  Peru  is  composed  of 


Volatile  oil  . . . . 69. 

Resin  very  soluble  in  alcohol  . ,20.7 

Do.  little  . . . 2.4 

Benzoic  acid  ....  6.4 

Extractive  matter  . . . 0.6 

Moisture  ....  0.9 


—100. 

The  oil  is  much  less  volatile  than  the  other  volatile  oils,  and  can- 
not be  separated  by  distillation.! 

2103.  The  principal  solid  resins  are,  rosin  or  colophan,  mastich,!  Solid  re- 
sandarach,  eletni,  guaiacum, § storax,  dragon’s  blood, II  benzoin,  and  sins- 
anime. 

2104.  Copal  is  the  most  important  of  this  class,  it  flows  from  the  CoPab 
rkus  copalinum  and  eloeocarpus  copaliferus  ; the  first  a native  tree  of 
America,  the  second  of  the  East  Indies.  It  is  white  with  a tint  of 
brown,  sometimes  opaque,  at  others  nearly  transparent.  It  differs 
from  other  resins  in  not  being  soluble  in  alcohol  nor  in  oil  of  turpen- 
tine without  peculiar  management.  Its  sp.  gr.  varies  from  1.045  to 
1.069. 

2105.  Its  solution  is  much  employed  as  a varnish,  in  the  forma- uses, 
tion  of  which  several  processes  are  followed. IF  The  following  me- 
thod is  recommended  by  Lenormand  : 


* Stoltze  in  Berlin  Juhrb.  xxvii.  2,  179. 

+ Balsam  of  Tolu  is  obtained  from  the  tulifera  balsamum,  it  is  reddish  brown,  be- 
comes brittle  by  exposure  to  the  air,  and  has  a fragrant  odour,  It  dissolves  in  ether, 
alcohol,  and  the  volatile  oils.  For  other  balsams  see  T.  Org.  Bodies , 520. 

t From  late  investigation  of  resins  it  appears  that  inastich  consists  of  two  resins ; 
the  one  soluble  and  acid,  the  other  insoluble  and  not  acid.  Johnson,  in  Phil.  Trans. 

April  1839. 

§ Guaiacum  is  rendered  blue  by  various  animal  and  vegetable  substances  ; it  becomes  Adulltriti#n  0f 
blue  when  rubbed  with  the  gluten  of  wheat,  or  the  farina.  It  is  often  adulterated  with  guaiacum1. 
common  rosin.  To  discover  this  fraud,  dissolve  the  guaiacum  in  caustic  potassa  ; if 
pure  the  solution  is  limpid,  but  muddy  if  rosin  be  present,  as  long  as  there  is  excess  of 
alkali. 

||  Lump  Dragon’s  blood  is  the  natural  and  pure  resin,  w'hile  the  strained  and  red  va- 
rieties, being  manufactured  articles,  are  more  or  less  decomposed  : it  contains  alcohol 
and  ether  with  considerable  tenacity,  but  they  may  be  expelled  by  long  exposure  to  a 
temperature  not  higher  than  200°.  Johnson,  Phil.  Trans.  April  1839. 

H Nicholson’s  Jour.  ix.  157;  T.  Org.  Bodies , 544;  Neil  in  Trans.  Soc.  of  Arts, 
xlix.  Ample  details  for  making  a great  variety  of  varnishes  are  given  in  Ure’s  Diet. 

Arts  and  Manuf.  1264. 

59 


466 


Chap.  IX. 

Solution  of 
copal. 


Lac. 


Solvents. 


Amber. 


Succinic 

acid. 


Gum  re- 
sins. 


Foetid  gum 
resins. 


Organic  Chemistry — Gum  Resins. 

Drop  upon  the  pieces  of  copal  pure  essential  oil  of  rosemary.  Those  pieces 
that  are  softened  by  the  oil  are  fit  for  the  purpose,  the  others  are  not.  Reduce 
them  to  a fine  powder  ; put  this  powder  into  a glass  vessel  not  thicker  than  a 
finger  breadth  ; pour  oil  of  rosemary  over  it,  and  stir  it  about  with  a glass  rod. 
In  a short  time  the  whole  is  converted  into  a thick  liquid.  Pour  alcohol  on  this 
liquid  by  little  at  a time,  incorporating  it,  by  gently  agitating  the  vessel,  till  it  is 
of  the  requisite  thinness  for  use.* 

2106.  Lac  is  an  important  resin  deposited  in  different  trees  in  the 
East  Indies,  viz.  ficus  indica , /.  religiosa , and  rhamnus  jujuba.  It 
flows  out  in  the  state  of  a milky  liquid,  in  consequence  of  the  punc- 
ture of  a small  insect,  the  coccus  ficus , on  the  branches  of  these  trees, 
made  by  the  insect  in  order  to  deposit  its  ova.  The  various  kinds  of 
lac  distinguished  in  commerce,  are  stick-lac , which  is  the  substance 
in  its  natural  state,  investing  the  small  twigs  of  the  tree ; seed-lac , 
which  is  the  same  broken  off;  and  which,  when  melted,  is  called 
shell-lac.  These  substances  have  been  examined  by  Hatchett. 
Their  component  parts  are  exhibited  below. t 

2107.  Water  dissolves  the  colouring  matter  of  lac,  and  alcohol  the 
resin  which  constitutes  the  chief  ingredient  of  lac.  A solution  of 
borax  in  water  dissolves  lac;  the  best  proportions  are  20  grs.  of  bo- 
rax, 100  grs.  of  lac,  and  4 ounces  of  water.  This  solution  mixed 
with  lampblack,  constitutes  Indian  ink.  Lac  contains  a peculiar 
body  called  laccin. 

2108.  Amber  is  a substance  which,  in  some  of  its  properties,  re- 
sembles resin  ; it  is  however,  very  sparingly  soluble  in  alcohol,  and 
difficultly  soluble  in  the  alkalies.  When  submitted  to  distillation,  it 
furnishes  an  acid  sublimate,  which  has  received  the  name  of  succinic 
acid.  It  is  found  in  beds  of  wood  coal. 


Section  III.  Gum  Resins. 

2109.  The  term  gum  resin  is  applied  to  a number  of  concrete  ve- 
getable juices  which  contain  various  proportions  of  resin,  gum,  and 
other  vegetable  principles.  They  are  opaque,  solid,  brittle,  or  some- 
times with  a fatty  appearance.  They  are  less  combustible  than  the 
resins;  they  do  not  melt  like  resins  but  are  softened  by  heat,  and 
swell.  They  burn  with  flame.  They  are  partially  soluble  in  water 
and  alcohol.  The  aqueous  solution  is  milky,  the  alcoholic  transpa- 
rent, but  becomes  milky  on  dilution.  Their  best  solvent  is  dilute 
alcohol. 

21 10.  Those  gum  resins  which  have  a fetid  or  alliaceous  odour,  are 
ammoniac,  galbanum,  assafcetida,  opoponax,  and  sagapenum.  The 
stimulating  gum  resinst  are  olibanum,  myrrh,  euphorbium,  and 
bdellium  ; the  first  is  the  frankincense  of  the  ancients. 


* Jour,  de  Chim.  iii.  218. 


t Restns 

Colouring  matter 

Wax 

Gluten 

Foreign  bodies  . 
Loss 


Stick- Lac. 

Seed-Lac. 

Shell-Lac. 

63 

88.5 

90.9 

.10 

2.5 

0.5 

6 

4.5 

4.0 

56 

2.0 

2.8 

6.5 

■ - — 

4.0 

2.5 

1.8 

-- 

■ 

100 

100 

100 

Phil.  Trane.  1894 

t Of  Thomson. 


Neutral  Vegetable  Principles.  4b 

2111.  The  cathartic  gum  resins  are  aloes,  scammonv.  and  gam-  Sect.iv. 
boge.  The  sedative  gum  resins  are  opium,  lactucarium* * * §  and  upas. 

2112.  Of  the  sedative  gum  resins  opium  is  the  most  important ; Opium, 
it  is  the  milky  juice  of  the  papaver  somniferum,  inspissated  into 

a dark  coloured  solid  by  exposure  to  the  atmosphere.  Its  best  sol- 
vent is  common  spirits.  Its  principal  constituents  have  been  al- 
ready described.  It  differs  much  in  its  qualities. 


Section  IV.  Neutral  Vegetable  Principles . 

2113.  Neutral  vegetable  principles  are  those  bodies  which  neither  Neutral 
possess  the  properties  of  acids  nor  bases,  and  which  so  far  as  is  principles, 
known,  do  not  combine  in  definite  proportions  with  other  substances. 

They  have  been  arranged  by  Thomson  in  thirteen  divisions. 

2114.  Amides , or  Amidets.  The  term  amide  signifies  an  anhy-  Division 
drous  ammoniacal  salt  deprived  (if  an  expression  apparently  contra-  Ami‘ 
dictory  may  be  allowed)  of  an  atom  of  water.  (1562) 

2115.  Oxamide . C202+NH2  = 44.  (T.)  This  was  discovered  by  Oxamide, 
Dumas  in  1830.1  When  oxalate  of  ammonia  is  heated  in  a glass  obtained 
retort,  it  loses  in  the  first  place  its  water  of  crystallization,  and  the 
crystals  become  opaque.  The  salt  then  melts  and  boils,  but  only  in 

those  parts  which  receive  immediately  the  impression  of  the  heat. 

Those  portions  which  melt  undergo  decomposition  and  disappear 
rapidly. $ When  the  distillation  is  at  an  end  some  trace  of  charcoal 
merely  remains  in  the  retort ; all  the  rest  has  been  volatilized.  In 
the  receiver  is  found  water  impregnated  with  carbonate  of  ammonia. 

This  water  holds  in  suspension  a flocky  matter  of  a dirty  white  co- 
lour.§ The  white  flocks  and  deposit  on  the  beak  of  the  retort  con- 
stitute the  substance  called  oxamide.  To  purify  it,  it  is  washed  out 
upon  a filter  and  thoroughly  edulcorated  with  cold  water.  Being 
nearly  insoluble,  it  remains  on  the  filter. 

2116.  The  gases  disengaged  during  the  distillation  change  their  Gases 
nature  as  it  proceeds;  they  are  ammonia,  then  carbonic  acid  and  evo  Te 
oxide,  and  cyanogen  ; water  and  carbonate  of  ammonia  are  also 
formed. II 

2117.  Oxamide  is  obtained  in  crystallized  plates,  or  as  a granular  Properties, 
powder.  When  pounded  and  well  washed  it  is  a dirty-white  pow- 
der, resembling  uric  acid,  without  taste  or  smell,  or  any  action  on 
vegetable  colours.  It  is  volatile,  and  crystallizes  when  cautiously 
heated  in  an  open  tube.  It  is  not  sensibly  soluble  in  cold  water  ; 

but  dissolves  in  boiling  water. 

2118.  Heated  in  sulphuric  acid  it  dissolves,  and  gas  is  given  out  Ac^on 
in  abundance,  consisting  of  equal  vols.  of  carbonic  acid  and  carbonic  of  S. 
oxide.  At  the  same  time  a quantity  of  ammonia  is  formed,  which 

* Lactucarium  is  obtained  from  the  juice  of  the  Lactuca  sativa  or  common  garden 
jettuce.  t Ann.  de  Chim.  et  de  Phys.  xliv.  129. 

t But  the  mass  in  general  retains  its  appearance,  and  a careful  examination  is  neces- 

sary to  be  able  to  perceive  the  thin  layer  of  the  salt  which  is  in  a state  of  fusion. 

§ The  neck  of  the  retort  exhibits  usually  crystals  of  carbonate  of  ammonia,  and  a 
thick  layer  of  the  same  white  matter. 

4 H Liebig  has  shown  that  when  caustic  ammonia  is  added  to  oxalic  ether,  alcohol  is 
evolved,  and  a copious  deposit  of  oxamide  is  produced.  This  is  by  far  the  most  eco- 
nomical method  of  preparing  oxamide.  See  Ann.  de  Pharm.  ix.  129.  T.  591. 


468 


Organic  Chemistry — Neutral  Vegetable  Principles. 


and  of  po- 
tassa. 

Analysis. 


Ether  oxa 
amide. 


Chap,  ix.  combines  with  the  acid.  Boiled  in  a concentrated  solution  of  po- 
tassa  it  gives  out  ammonia  in  abundance,  with  the  formation  of  oxalic 
acid  which  combines  with  the  potassa. 

2119.  According  to  the  analysis  of  Dumas*  its  constituents  appear 
to  be  C2O2-I-H2N  = 44.0.  If  we  add  HO  (an  atom  of  water),  the 
oxamide  becomes  C2O3-I-H3N,  or  oxalate  of  ammonia.!  t.  592. 

2120.  Fit  her  oxamide  is  obtained  when  a current  of  dry  ammonia- 
cal  gas  is  passed  over  a given  quantity  of  pure  oxalic  ether.  Sitcci- 
namide  is  formed  when  the  same  gas  is  made  to  act  upon  anhydrous 
succinic  acid.  Benzamide  is  obtained  when  the  gas  is  absorbed  by 
pure  chloride  of  benzoul.  Sulphamide  is  formed  when  dry  ammo- 
niacal  gas  is  combined  with  anhydrous  sulphuric  acid. 

2121.  This  division  comprises  benzoyl  and  its  compounds.! 

2122.  The  base  of  benzoic  acid  has  been  termed  by  Liebig  and 
Wohler  benzoyl,  and  was  obtained  by  Laurent  by  passing  a current 
of  chlorine  gas  through  benzoin  kept  in  fusion  while  the  gas  was 
passing;  hydrochloric  acid  was  formed  and  benzoyl  disengaged.  It 
was  purified  by  solution  in  alcohol  and  crystallization. 

2123.  The  volatile  oil  of  bitter  almonds  is  a hydret  of  benzoyl, 
and  this  oil  has  the  property  of  absorbing  oxygen  and  of  being  con- 
verted into  benzoic  acid.  The  change  may  be  thus  explained: 


Division 

2d. 

Benzoyl. 


: 


The  oil  is 
Benzoic  acid 


CuHg  O2 
ChH5  03 


Explana- 

tion. 


Properties. 


Analysis. 


So  that  the  oil  contains  1 atom  more  of  hydrogen,  and  l atom  less  of 
oxygen,  than  the  acid  ; 2 atoms  of  oxygen  are  absorbed,  the  one 
unites  with  1 atom  of  hydrogen  and  forms  water,  while  the  other 
combines  with  (CuH502)  and  converts  it  into  benzoic  acid.  C,4H502 
must  be  the  base  of  benzoic  acid,  and  the  oil  must  be  this  base  com- 
bined with  an  atom  of  hydrogen,  or  a hydret  of  benzoly.  t, 

2124.  Benzoyl  is  slightly  yellow,  without  taste  or  smell ; insoluble 
in  water,  very  soluble  in  alcohol  and  ether,  crystallizing  in  six-sided 
prisms.  Its  lustre  is  vitreous.  It  may  be  volatilized  without  decom- 
position ; becomes  solid  at  about  196°  ; burns  on  platinum  with  a 
red  flame,  t.  603. 

The  analysis  afforded 

Carbon  . 14  atoms  per  cent.  80. 

Hydrogen  . 5 “ “ “ 4.76 

Oxygen  2 “ “ “ 15.24 

100. 

Com-  2125.  The  compounds  of  benzoyl  and  their  composition  are  the 

pounds  of  r 11  r * r 

Benzoyl.  following : 

Benzoyl  ...  C14H5  O2 

Hydret  of  “ or  oil  of  bitter  almonds  C14H5  Oa  H 
Benzoin  -----  C14H5  O2  + H 

Benzoic  acid  - ChHs  O2  + O 

Chloride  “ » »>  - - C14H5  O2  4-  Cl 

Bromide  u * - - C14H5  Oa  -f  Br 

Iodide  “ - - - C14H5O2-I-I 

Sulphuret  w ...  CmHg  O2  -f-  3 

Cyanide  “ - - - Ci4Hs  O2  + C2  N 


* Ann.  de.  Chim.  et  de  Phys.  xliv.  129,  and  Jour,  de  Pharm.  xvii.  177. 
1 NH2+C2O2,  «q-  44.39.  L.  762.  t Bentule.  Tand  L. 


Sugar . 


469 


Benzone* * * §  ChH5C)  Sect.  IV. 

Benzinet  C6H3.  Now,  2(C6H3)4-2(C02)=Ci4H 5024-02  

Benzamide  C14H  502-|-H  2^ 

Benzimide  C14H  5024"HiN^  ? 

Nitrobenzidei  2(C6  H g^-j-NO^ 

Sulphobenzide  2(C6  H 3)-|-S03 
Azotobenzide§  2(C6H3)-j-N 

2126.  Spiroil  and  its  compounds.  Spiroil  is  the  supposed  base  of  Division 
the  volatile  oil  extracted  from  the  flowers  of  the  spiraea  ulmaria.  It  3d* 

is  a compound  of  C12H504  with  an  atom  of  hydrogen.  It  has  not 
been  obtained  in  a separate  state,  but  it  has  been  combined  with  ox- 
ygen, chlorine,  bromine,  iodine  and  hydrogen,  and  shown  to  form 
definite  compounds  with  each. 

2127.  Sugar.  C12H10O10  = 162.24.  The  term  sugar  has  been  Division 

applied  to  various  substances  characterized  by  a sweet  taste.  4th‘ 

2128.  Sugar  may  be  extracted  from  the  juice  of  a number  of  ve-  Sugars, 
getables,  and  is  contained  in  all  those  having  a sweet  taste  ; that 
which  is  commonly  employed  is  the  produce  of  the  arundo uon  0 ’ 
saccharifera , or  sugar-cane,  a plant  which  thrives  in  hot  climates. 

Its  juice  is  expressed  and  evaporated  with  the  addition  of  a small 
quantity  of  lime,  until  it  acquires  a thick  consistency  ; it  is  then 
transferred  into  wooden  coolers,  where  a portion  concretes  into  a 
crystalline  mass,  which  is  drained  and  exported  under  the  name  of 
muscovado , or  raw  sugar.  The  remaining  liquid  portion  is  molasses , Molasses 
or  treacle.  A gallon  of  juice  yields  on  an  average  about  a pound  of 
raw  sugar. 

2129.  The  juice,  which  flows  spontaneously  from  incisions  made  Varieties  of 
in  the  American  maple-tree,  affords  a quantity  of  sugar  sufficient  su°ar‘ 

to  render  it  a process  worth  following.  The  juice  of  the  carrot,  the 
melon, II  and  still  more  remarkably  of  the  beet  ( beta  vulgaris , L.) 
yields  a considerable  proportion  of  sugar.  To  obtain  it  from  the  lat- 
ter vegetable,  the  roots,  softened  in  water,  are  to  be  sliced,  and  the 
juice  expressed.  It  is  then  to  be  boiled  down,  with  the  addition  of  a Beet  sugar, 
little  lime,  till  about  two  thirds  remain,  and  afterwards  strained. 

These  boilings  and  strainings  are  repeated  alternately,  till  the  liquid 
attains  the. consistence  of  syrup,  when  it  is  left  to  cool.  The  su- 
gar thus  extracted,  retains  somewhat  of  the  taste  of  the  root ; but  it 
may  be  purified  by  the  operation  used  for  the  refining  of  West  India 
sugar,  and  it  then  loses  its  peculiar  flavour.  The  quantity  obtained 
varies  considerably  ; but  in  general  it  may  be  stated  at  between  four 
and  five  pounds  from  100  lbs  of  the  root,  besides  a proportion  ot  un- 
crystallizable  syrup.  In  Germany  the  expense  has  been  calculated 
at  about  three  pence  per  pound. H 

* This  term  was  applied  from  the  analogy  between  benzone  and  acetone,  the  name 
given  by  Dumas  and  Liebig  to  the  liquid  formerly  called  pyroacetic  spirit. 

+ The  benzine  of  Mitscherlich  is  the  same  with  the  bicarburet  of  hydrogen  of  Fa- 
raday. 

t Formed  when  nitric  acid  is  made  to  act  upon  his  benzin. 

§ A substance  obtained  by  distilling  a mixture  of  nitrobenzide  and  lime.  For  de- 
tails respecting  these  compounds,  see  Thomson’s  Org.  Bodies , 604. 

||  Quart.  Jour.  N.  S.  1.  239. 

IT  See  Chaptal  On  the  manufacture  of  Sugar  in  France,  Phil.  Mag.  xlvii.  331.  For 
details  respecting  the  manufacture  and  refining  of  sugar,  see  Ure’s  Did . Arts  and 
Manuf.  1191. 


470 


Organic  Chemistry — Sugar. 


Chap.  IX. 

Action  of 
sulphuric 
acid, 


Of  nitric 
acid, 


Of  acids  in 
general. 


Absorbs 

ammonia. 


Solvents. 


Effect  of 
heat. 


Product  of 
its  distilla- 
tion. 


Liquid  su- 
gar. 


Sugar  of 
grapes. 


2130. '  Sugar  is  altered  by  the  action  of  the  strong  acids.  Con- 
centrated sulphuric  acid  poured  upon  sugar  blackens  it,  and  causes  it 
to  deposit  a charry  matter  when  we  dilute  the  acid  with  water.  When 
long  boiled  with  this  acid  it  is  converted  into  sugar  of  grapes,  or  that 
species  of  sugar  into  which  starch  is  converted  by  the  same  process. 

2131.  By  nitric  acid  it  is  converted  into  oxalhydric  and  oxalic 
acids : 480  grs.  of  sugar,  treated  with  6 ounces  of  nitric  acid,  diluted 
with  its  own  weight  of  water,  and  cautiously  heated,  separating  the 
crystals  as  they  are  formed,  yielded  280  grs.  of  oxalic  acid.  So  that 
100  parts  of  sugar  yield  by  this  treatment  58  parts  of  oxalic  acid.* 
Hydrochloric  acid  acts  upon  sugar  like  the  sulphuric.  When  chlo- 
rine is  passed  through  a solution  of  sugar,  it  transforms  it  into  oxal- 
hydric acid,  while  the  chlorine  is  converted  into  hydrochloric  acid. 

2132.  Malagutti  and  Bouchardtt  have  lately  ascertained  that  acids, 
in  general,  even  when  very  dilute,  act  upon  sugar  in  the  same  man- 
ner when  assisted  by  heat.  They  first  convert  it  into  uncrystallizable 
sugar,  then  into  sugar  of  grapes,  then  into  uncrystallizable  sugar, 
then  into  ulmic  acid ; and  finally,  if  atmospheric  air  be  present,  into 
ulmic  and  formic  acids. 

2133.  Sugar  combines  with  the  acidifiable  bases.  When  intro- 
duced into  ammonia,  over  mercury,  it  absorbs  the  gas,  diminishes 
in  bulk,  becomes  coherent,  compact,  and  soft,  so  that  it  can  be  cut 
with  a knife,  and  gives  out  an  ammoniacal  smell. 

2134.  Sugar  is  soluble  in  alcohol,  but  not  in  so  large  a proportion 
as  in  water.  When  the  solution  is  set  aside  it  deposits  crystals.  It 
unites  with  oils,  and  renders  them  miscible  with  water.  A moderate 
quantity  of  it  retards  the  coagulation  of  milk ; but  a large  quantity 
promotes  it. 

2135.  When  heated  sugar  melts,  swells,  becomes  brownish  black, 
and  exhales  a peculiar  smell  known  in  French  by  the  name  caromeh 
At  a red  heat  it  bursts  into  flame.  See  Appendix. 

2136.  When  distilled  in  a retort  sugar  yields  water,  pyromucic 
acid,  empyreumatic  oil,  and  a bulky  charcoal.  When  a solution  of 
sugar  is  used  carbonic  acid  and  carburetted  hydrogen  are  obtained. 
It  is  therefore  decomposed  by  heat.t 

2137.  Liquid  sugar  exists  in  a variety  of  fruits  and  vegetable  juices. 
It  is  distinguished  by  being  uncrystallizable.  It  may  be  obtained 
from  the  stalks  of  the  zea  mays , or  Indian  corn  and  constitues  a con- 
siderable portion  of  the  molasses  of  common  sugar. 

2138.  Sugar  of  grapes.  C12Hl20I2.  Verjuice,  or  the  liquid  ob- 
tained from  unripe  grapes,  contains  tartar,  sulphate  of  potassa,  sul- 
phate of  lime,  much  citric  acid,  a little  malic  acid,  extractive,  and 
water,  but  neither  guin  nor  sugar.  As  the  grapes  advance  to  matu- 
rity, the  citric  acid  disappears,  and  gum  and  sugar  appear  in  its  place. 
The  ripe  grape  juice  yields  from  a third  to  a fifth  of  solid  matter. 

* Cruickshanks,  Rollo  on  Diabetes , 460.  + Jour,  de  Pharm.  xxi.  440,  and  627. 

t For  the  result  of  Prout’s  analysis  of  sugar,  see  Phil.  Trans.  1827. 

Fremy  obtained  an  oily  looking  matter  lrom  1 part  sugar  and  8 parts  lime,  which 
yielded  acetone  CqH^O  and  metacetone  C5H5O.  Two  atoms  of  sugar  may  be  re- 
solved into  3 atoms  metacetone. 6 atoms  carbonic  acid  and  7 atoms  water ; and  1 atom  of 
sugar  into  3 atoms  of  acetone,  3 atoms  of  carbonic  acid  and  2 atoms  water  (T.  636). 
Starch  and  gum  distilled  with  lime  afford  the  same  products. 


471 


Amylaceous  Substances. 

The  sugar  may  be  extracted  with  the  aid  of  potassa  and  heat.  It  is  Sect.  iv. 
less  sweet  than  that  from  sugar  cane. 

2139.  Starch  may  be  converted  into  a sugar  possessing  the  pro-  Conversion 
perties  of  sugar  of  grapes,  by  mixing  it  with  about  4 times  its  weight  starch 
of  water,  and  about  part  of  its  weight  of  sulphuric  acid,  boiling in  0 sugar" 
for  36  hours,  supplying  water  as  it  evaporates,  saturating  the  acid 

with  lime,  separating  the  sulphate  of  lime  and  concentrating. 

2140.  Honey  is  also  a variety  of  sugar  containing  a crystallizable 
and  an  uncrystallizable  portion  ; the  predominance  of  one  or  other  of 
which  gives  to  it  its  peculiar  character ; they  may  be  partially  sepa- 
rated by  mixing  the  honey  with  alcohol,  and  pressing  it  in  a linen 
bag;  the  liquid  sugar  being  the  most  soluble,  passes  through,  leaving 
a granular  mass,  which  forms  crystals  when  its  solution  in  boiling 
alcohol  is  set  aside.  Honey  also  frequently  contains  wax,  and  a 
little  acid  matter. 

2141.  Manna  is  an  exudation  from  the  Fraxinus  ornus,  a species  Manna 
of  ash,  growing  in  Sicily  and  Calabria.  It  exists  in  the  leaves  of 
celery  and  several  other  plants.  To  obtain  pure  manna,  dissolve 

the  manna  of  the  shops  in  boiling  alcohol  and  allow  it  to  cool ; the 
manna  crystallizes.  It  has  a sweet  and  somewhat  nauseous  taste, 
and  is  used  in  medicine  as  a mild  aperient.  The  sweetness  of  manna 
is  owing,  not  to  sugar,  but  to  a distinct  principle  called  mannite.  Its 
solution  in  water  does  not  appear  susceptible  of  vinous  fermentation. 

2142.  Liquorice  sugar  is  the  inspissated  juice  of  the  glycyrrhiza  Ljquorjce 
glabra  a native  of  Spain.  It  combines  with  bases  and  with  salts,  sugar. 

It  precipitates  the  greater  number  of  metallic  solutions. 

2143.  Glycerin.  CGH705=83.  (T.)  This  substance  was  called  Glycerin, 
by  Scheele  sweet  principle  of  oils. 

To  obtain  it  an  oil  may  be  digested  with  an  alkaline  ley  till  converted  into  pr0cess. 
soap.  The  soap  being  separated,  the  alkaline  liquid  is  saturated  with  sulphuric 
acid,  and  any  excess  of  acid  removed  by  carbonate  of  baryta.  Filter  and  evapo- 
rate to  the  consistence  of  a syrup  : dissolve  the  syrup  in  alcohol  and  filter  ; evap- 
orate the  alcoholic  solution  ; the  glycerin  remains. 

2144.  It  is  a colourless  syrup,  uncrystallizable,  of  a sweet  taste  Properties, 
and  without  smell.  From  the  analysis  of  Liebig  and  Pelouze  1 

atom  of  glycerin  is  combined  in  stearin  with  2 atoms  of  stearic  acid. 

2145.  Amylaceous  substances.  When  wheat  flour  is  formed  into  a Division 
paste  with  water,  and  then  held  under  a small  stream  of  water,  5th‘ 
kneading  continually  till  the  water  runs  off  colourless,  the  flour  is  oU?ySub-* 
divided  into  two  constituents  gluten  and  starch.  The  starch  is  re-  stances, 
moved  by  the  water  and  subsides  on  standing. 

2146.  The  common  process  for  obtaining  the  starch  of  wheat  consists  in  process  for 
steeping  the  grain  in  water  till  it  becomes  soft;  it  is  then  put  into  coarse  linen  obtaining 
bags,  which  are  pressed  in  vats  of  water;  a milky  juice  exudes,  and  the  starch  starch. 
falls  to  the  bottom  of  the  vat.  The  supernatant  liquor  .undergoes  a slight  fer- . 
mentation,  and  a portion  of  alcohol  and  a little  vinegar  is  formed,  which  dis- 
solves some  impurities  in  the  deposited  starch ; it  is  then  collected,  washed,  and 

dried  in  a moderate  heat,  during  which  it  splits  into  the  columnar  fragments 
which  we  meet  with  in  commerce,  and  which  are  generally  rendered  slightly 
blue  by  a little  smalt. 

2147.  Starch  or  Fecula , may  be  separated  from  a variety  of  sub- 
stances ; and  many  roots.  By  diffusing  the  powdered  grain  or 
the  rasped  root  in  cold  water,  the  grosser  parts  may  be  separated  by 


472 


Organic  Chemistry — Amylin. 


Chap  IX. 


Arrowroot. 

Sago. 


Properties 
of  starch. 


Insoluble 
iu  alcohol, 
&c. 

Composi- 
tion of 
starch. 


Amidin. 


Amylin. 


Analysis. 


a strainer  and  the  liquor  which  passes  deposits  the  starch,  which  is 
to  be  washed  in  cold  water  and  dried  in  a gentle  heat. 

2148.  Arrow  root  consists  entirely  of  very  pure  starch.  It  is  ex- 

tracted from  the  potato,  and  the  roots  of  the  jatropha  manihot  afford 
the  variety  known  as  cassava  and  tapioca.  Sago , another  variety, 

is  extracted  from  the  pith  of  a species  of  palm  the  sagus  raphia 
which  grows  in  the  East  India  Islands.*  Salop  comes  from  Persia 
and  is  supposed  to  be  the  prepared  roots  of  different  species  of 
orchis.  Of  rice,  starch  constitutes,  according  to  Braconnot,  from  83 
to  85  per  cent. 

2149.  Pure  starch  is  a white  substance,  insoluble  in  cold  water, 
but  readily  soluble  at  a temperature  between  160°  and  180°.  Its 
solution  is  gelatinous,  becomes  mouldy  and  sour  by  exposure  to  air, 
and  by  careful  evaporation  yields  a substance  resembling  gum  in 
appearance,  which  is  a compound  of  starch  and  water.  Starch  is 
insoluble  in  alcohol  and  in  ether  ; its  most  characteristic  property  is 
that  of  forming  a blue  compound  with  iodine. 

2150.  Starch  consists  essentially  of  two  distinct  substances. 

1.  The  liquid  portion  which  fills  each  little  vesicle  composing  it,  and 
this  liquid  consists  of  water  holding  in  solution  a peculiar  substance 
which  is  called  amidin. t 2.  The  vesicular  portion  of  the  grain, 

insoluble  in  water,  and  called  amylin.\  According  to  Guerin — 
Vary,  potato  starch  is  composed  of 

Exterior  tegumentary  amylin,  - 2.12 

Amidin 38.13 

Amylin 59.75 

100§ 

2151.  Amidin  or  the  soluble  part  of  starch  has  neither  taste  nor 
smell.  Cold  water  dissolves  it,  but  it  is  more  soluble  in  boiling 
water:  it  is  insoluble  in  alcohol  and  ether.  Its  aqueous  solution 
soon  becomes  acid.  Digested  in  nitric  acid  it  forms  oxalhydric  acid, 
and  then  oxalic  acid.  100  parts  of  amidin  and  250  of  sulphuric 
acid  at  the  temperature  of  150°  furnish  95.8  parts  of  anhydrous 
sugar. 

2152.  Amylin  is  insoluble  in  water,  it  does  not  dissolve  in  boiling 
water,  nor  in  alcohol  or  ether;  but  it  swells  in  water  and  becomes 
white.  When  100  parts  are  digested  with  800  of  nitric  acid,  25.46 
parts  of  anhydrous  oxalic  acid  are  formed.  When  digested  in  sul- 
phuric acid  and  water  it  is  converted  into  sugar:  100  parts  of  amy- 
lin  give  110.57  of  hydrous  sugar. 

From  pure  amylin  Prout  obtained 

Carbon 43.31 

Hydrogen  ------  6.49 

Oxygen 50.20 

100 

Numbers  which  lead  to  the  conclusion  that  it  is  composed  of  12  atoms  carbon, 
10  hydrogen  and  10  oxygen.  (T.) 

It  is  probable  that  the  dextrine  of  Biot  and  Person  consists  chiefly  of  amidin. 
T.  656. 


* See  an  account  of  its  preparation  in  Forest’s  Voyage,  p.  3f. 
t Vary  in  Ann.  de  Chim.et  de  Phys.  Ivi.  231. 

t From  the  Greek  word  apvl or  starch.  § Jour,  de  Pharm , xxii.  210. 


Xyloidin.  473 

2153.  Hordein  may  be  obtained  from  barley*meal  made  into  a Sect.  iv. 
paste  with  water  and  washed  by  a current  of  water  dropping  on  it.  Hordein. 
The  starch  and  hordein  are  washed  away.  By  boiling  in  acidulous 
water,  the  starch  is  taken  up,  and  the  hordein  remains  unaltered.  It 
amounts  to  from  54  to  56  per  cent,  of  the  meal. 

2154.  It  is  a yellow  powder,  resembling  sawdust ; insoluble  in  Properties, 
water  and  alcohol,  does  not  yield  ammonia  ; but  yields  oxalic  and 

acetic  acids.  During  the  malting  of  barley,  the  hordein  is  converted 
into  starch. 

2155.  Lichenin  is  the  name  given  to  what  was  once  called  the  Lichenin. 
starch  of  the  cetraria  islandica  or  Iceland  moss,  which  when  good 
yields  about  44^-  per  cent.  In  cool  water  it  swells  up  but  does  not 
dissolve.  It  is  coloured  blue  by  iodine,  and  is  precipitated  by  alco- 
hol. It  appears  to  be  isomeric  with  amidin.  According  to  Herber- 

ger  it  is  poisonous.* 

2156.  Inulin  is  obtained  from  the  roots  of  the  inula  helenium , Inulin. 
colchicum  autumnale,  and  more  abundantly  from  the  dahlia  'purpurea. 

It  is  a fine,  white,  tasteles  powder.  It  is  precipitated  from  its  aque- 
ous infusion  by  infusion  of  nut-galls. 

2157.  Lignin  or  woody  fibre  constitutes  the  fibrous  structure  of  lignin, 
vegetable  substances,  and  is  the  most  abundant  principle  in  plants. 

The  different  kinds  of  wood  contain  about  96  per  cent,  of  lignin.  It 
is  prepared  by  digesting  the  sawings  of  any  kind  of  wood  succes- 
sively in  alcohol,  water,  and  dilute  hydrochloric  acid,  until  all  the 
substances  soluble  in  these  menstrua  are  removed. 

2158.  Lignin  has  neither  taste  nor  odour,  undergoes  no  change  by  Propertie  s. 
keeping,  and  is  insoluble  in  alcohol,  water,  and  the  dilute  acids.  By 
digestion  in  a concentrated  solution  of  pure  potassa,  it  is  converted 
according  to  Braconnot  into  a substance  similar  to  ultnin.  Mixed 

with  strong  sulphuric  acid  it  suffers  decomposition,  and  is  changed 
into  a matter  resembling  gum  ; and  on  boiling  the  liquid  for  some 
time  the  mucilage  disappears,  and  a saccharine  principle  like  the 
sugar  of  grapes  is  generated.  Braconnot  finds  that  several  other 
substances  which  cpnsist  chiefly  of  woody  fibre,  such  as  straw,  bark, 
or  linen,  yield  sugar  by  a similar  treatment.! 

2159.  Xyloidin  is  a substance  obtained  by  the  action  of  con- Xyloidin. 
centrated  nitric  acid  on  starch,  lignin  and  some  other  substances. 

When  the  acid  of  density  1.5  is  added  to  starch,  a solution  is  ob- 
tained, which  if  treated  immediately  with  water,  deposits  the 
xyloidin. 

Xyloidin  is  a compound  of  nitric  acid  and  starch,  an  atom  of 
water  in  common  starch  being  replaced  by  an  atom  of  nitric  acid.! 

It  is  very  combustible. § 

2160.  The  exudations  from  various  trees  and  plants  which  have  Division 
been  called  gums,  may  be  arranged  under  three  genera,  viz.  arabin , 
bassorin  and  cerasin. 

2161.  The  term  Arabin  was  applied  by  Chevreul  to  gum  arabic,  Arabin. 


* Jour,  de  Pharm.  xvii.  229. 

+ Ann  de  Chim . et  de  Phys.  xii.  For  other  principles  of  this  division  see  T.  Org, 
Bodies. 

t Pelouze.  § See  Jour,  of  the  Frank . Instit.  xxiv.  119. 

60 


474 


Chap.  IX. 


Properties. 


Uses. 


Action  of 
sulphuric 
acia. 


Bassorin. 


Cerasin. 


Division 

7th. 

Glutinous 

substances. 

Properties. 


Albumen. 


Organic  Chemistry — Albumen. 

which  consists  almost  entirely  of  arabin.  Gum  arabic  comes  from 
the  Levant  but  its  use  has  been  in  a great  measure  superseded  in 
G.  Britain  by  gum  Senegal.  It  is  in  small  rounded  drops  or  tears, 
sp.  gr.  is  1.355.  It  is  composed  of 

Arabin  - - - - 79.4 

Ashes  . - l . . . . 3.0 

Water 17.6 

100 

2162.  Arabin  is  colourless,  tasteless,  inodorous,  and  transpa- 
rent, friable  when  dry,  tough  when  moist.  It  softens  at  a tempera- 
ture between  282°  and  392°  and  may  be  drawn  out  into  threads.  It 
is  insoluble  in  alcohol.  With  water  it  forms  mucilage. 

It  is  viscid  and  glutinous,  and  is  used  by  calico-printers  to  thicken 
their  colours  and  mordants  to  prevent  their  spreading  on  the  cloth. 
It  may  be  kept  for  years  without  much  change,  but  finally  becomes 
acid. 

2163.  Boiled  with  sulphuric  acid  it  is  converted  into  sugar,  but 
which  differs  from  starch  sugar  in  not  fermenting  with  yeast.  With 
nitric  acid  it  yields  mucic  and  oxalic  acids.  Its  atomic  composition 
is  the  same  as  that  of  sugar  in  crystals. 

2164.  The  principal  varieties  of  gum  consisting  altogether  or 
chiefly  of  arabin,  are  gum  arabic,  gum  Senegal  and  mucilage  of 
lintseed. 

2165.  Bassorin  was  first  noticed  by  Vauquelin  in  a gum  from 
Bass  ora.  When  this  gum  is  treated  with  water,  the  bassorin  re- 
mains in  a gelatinous  form.  It  has  since  been  found  in  gum  traga- 
canth  and  cherry-tree  gum.  It  is  solid,  colourless,  insipid  and  ino- 
dorous ; insoluble  in  water,  but  swells  up  and  becomes  a jelly.  It 
is  insoluble  in  alcohol.  By  the  action  of  nitric  acid  mucic  and 
oxalic  acids  are  formed.  With  sulphuric  acid  it  forms  a crystalliza- 
ble  sugar. 

2166.  Cerasin  is  the  name  given  to  a substance  in  cherry-tree 
gum  which  remains  undissolved  when  that  gum  is  treated  with  cold 
water.  It  is  isomeric  with  arabin.  It  is  solid,  insipid  and  inodo- 
rous; insoluble  in  alcohol,  swells  in  cold  water,  but  does  not  dis- 
solve. When  boiled  in  water  it  is  converted  into  arabin.* 

2167.  Gluten  may  be  obtained  from  wheat-flour,  by  forming  it 
into  a paste  and  washing  it  under  a small  stream  of  water.  The 
starch  is  thus  washed  away,  and  a tough  elastic  substance  remains, 
which  is  gluten. 

Its  colour  is  gray,  and,  when  dried,  it  becomes  brown  and  brittle. 
It  is  nearly  insoluble  in  water  and  in  ether.  When  allowed  to 
putrefy  it  exhales  an  offensive  odour,  and  when  submitted  to  de- 
structive distillation,  it  furnishes  ammonia,  a circumstance  in  which 
it  resembles  animal  products.  Most  of  the  acids  and  the  alkalies 
dissolve  it. 

Gluten  has  been  resolved  by  modern  chemists  into  four  distinct 
principles,  viz.  albumen , emulsin , mucin , and  glutin. 

2168.  Albumen.  When  fresh  gluten  is  digested  in  hot  alcohol  till 
every  thing  soluble  is  takeu  up,  a bulky  substance  of  a grayish 


* Calendulin  is  obtained  from  the  flower  of  the  calendula  officinalis,  or  Marygold. 
Saponin  was  discovered  in  the  root  of  the  saponaria  officinalis . 


Caoutchouc . 475 

colour  remains,  which  constitutes  what  has  been  called  vegetable  s«ct.  iv. 
albumen.  It  is  soluble  in  water ; but  coagulates  when  heated.  It 
is  insoluble  in  alcohol  and  ether.  When  dry  it  is  opaque.  It  is  pre- 
cipitated from  acid  solutions,  by  carbonate  of  ammonia. 

2169.  Emulsin  is  the  name  given  to  a peculiar  substance  which  Emulsin 
exists  in  almonds,  and  which  has  the  property  of  decomposing  mu  m* 
amygdalin,  and  of  forming  hydrocyanic  acid  and  volatile  oil  of  bit- 
ter almonds. 

2170.  Mucin  is  obtained  when  alcohol  is  boiled  upon  the  gluten  Mucin 
of  wheat.  It  dries  into  transparent  grains,  burns  like  animal  mat- 
ter; is  more  soluble  in  water  than  gluten,  and  constitutes  about  4 

per  cent,  of  the  gluten  of  wheat  flour.  100  parts  of  hot  water  dis- 
solve 4 parts  of  mucin,  and  the  solution  soon  putrefies. 

2171.  The  aqueous  solution  of  mucin  is  precipitated  by  infusion 
of  nutgalls,  slightly  by  alcohol.  When  made  into  a paste  with 
starch  and  kept  for  10  hours  at  145°  it  converts  the  starch  into 
sugar  and  dextrine. 

2172.  Glutin  may  be  obtained  by  boiling  alcohol  upon  the  gluten  Glutin  ob- 
of  wheat  and  freeing  the  solution  from  mucin  by  repeated  precipita-  tained. 
tions.  On  evaporating  the  alcohol  the  glutin  is  left  as  a yellowish 
translucent  matter. 

2173.  Glutin  is  almost  insoluble  in  water,  but  soluble  in  alcohol,  Characters, 
ether,  dilute  acids  and  caustic  alkaline  leys.  It  is  precipitated  by 
infusion  of  nutgalls.* 

2174.  Caoutchouc,  elastic  gum  or  Indian  rubber,  is  the  concrete 

juice  of  the  Hcevea  caoutchouc  and  Iatropa  elastica , natives  of  South  ^ision 
America,  and  of  the  Ficus  Indica  and  Artocarpus  integrifolia , Caout- 
which  grow  in  the  East  Indies.  It  is  a soft  yielding  solid,  of  a chouc. 
whitish  colour  when  not  blackened  by  smoke,  possesses  considera- 
ble tenacity,  and  is  particularly  remarkable  for  its  elasticity.!  It  is 
inflammable,  and  burns  with  a bright  flame.  It  is  insoluble  in  water 
and  alcohol ; but  it  dissolves,  though  with  some  difficulty,  in  pure 
ether.  It  is  very  sparingly  dissolved  by  the  alkalies,  but  its  elasti- 
city is  destroyed  by  their  action.  By  the  sulphuric  and  nitric  acids 
it  is  decomposed,  the  former  causing  deposition  of  charcoal,  and  the 
latter  formation  of  oxalic  acid. 

2175.  Caoutchouc  is  soluble  in  the  essential  oils,  spirits  of  turpen- 
tine, ether,  naphtha,  cajeput  oil,  and  in  the  volatile  liquid  obtained 
by  distilling  caoutchouc  ; and  from  all  these  solvents,  except  the 
essential  oils,  it  is  left  on  evaporation  without  loss  of  its  elasticity. 


* Zein  is  the  name  given  by  Gorham  (Jour,  of  Scien.  xi.  205.)  to  the  gluten  of  zea  zein. 
mats  or  Indian  corn.  According  to  Gorham  it  contains  no  nitrogen  and  yields  no 
ammonia  when  distilled ; but  Bizio  affirms  that  he  obtained  ammonia  from  it. 

Viscin  is  obtained  from  bird-lime  3 which  is  prepared  from  the  middle  bark  of  the  vi.cin, 
holly  boiled  in  water  and  deposited  in  pits  till  it  becomes  viscous. 

Pollenin  is  a peculiar  substance  found  in  the  pollen  of  the  pinus  abies , lycopodium  p0iienin. 
clavatum,  &c. 

Legumin  is  contained  in  the  cotyledons  of  the  seeds  of  papilionaceous  plants.  L#gumin. 

Amygdalin  exists  in  the  bitter  almond.  Amygdalin. 

Glairin  is  the  name  applied  to  a substance  observed  in  the  sulphureous  waters  of  Giairin. 
some  springs.  It  gelatinizes  by  concentration.  Decomposed  it  yields  ammonia.  It 
is  probably  of  vegetable  origin. 

t For  some  curious  experiments  on  the  connection  between  the  temperature  of 
caoutchouc  and  its  elasticity  see  T.  Org.  Bodies , 696,  and  Manchester  Memoirs , ii. 

2d  series. 


476 


Organic  Chemistry — Caoutchouc. 


Chap.  IX. 


Preparation 
of  caou- 
tchouc. 


Effect  of 

heat. 


Use*. 


Before  actually  dissolving,  the  caoutchouc  swells  up  remarkably, 
and  acquires  a soft  gelatinous  aspect  and  consistency  ; in  this  state 
it  is  used  for  rendering  cloth  and  leather  impervious  to  water,  and, 
as  suggested  by  Mitchell,  may  be  cut  with  a wet  knife  into  thin 
sheets  or  bottles,  and  be  extended  to  a great  size.* 

In  preparing  caoutchouc  for  the  action  of  spirits  of  turpentine, 
ammonia  is  now  used  with  advantage.  The  caoutchouc  is  cut  into 
shreds,  covered  with  caustic  ammonia,  and  left  in  this  state  several 
months  ; it  becomes  soft,  swells,  but  is  still  elastic.  It  is  then  treat- 
ed with  spirits  of  turpentine,  and  by  agitation  converted  into  an 
emulsion  ; in  a short  time  it  swims  on  the  surface,  and  may  be 
removed.  A much  smaller  quantity  of  turpentine  is  required  when 
the  caoutchouc  has  been  thus  softened. 

2176.  When  caoutchouc  is  cautiously  heated,  it  fuses  without  de- 
composition ; but  at  a higher  temperature  it  is  resolved  into  a volatile 
liquid  of  a brown  colour,  which  amounts  to  -^ths  of  the  original 
caoutchouc.  When  carefully  rectified,  a very  volatile  liquid  of  sp. 
gr.  0.64  is  obtained,  which  is  very  combustible  and  burns  with  a 
bright  flame,  mingles  with  alcohol,  and  dissolves  copal  and  other 
resins.  It  is  very  useful  as  a solvent  for  caoutchouc  and  for  the  pre- 
paration of  varnishes. 

2177.  Caoutchoucjin  thin  sheets  is  exceeding  useful  in  the  labo- 
ratory, for  joining  glass  tubes,  &c.  so  as  to  make  an  air  tight  joint 
and  at  the  same  time  preserve  flexibility. 

2178.  The  milky  juice  carried  from  South  America  was  found  by 
Faraday  to  be  composed  of 

Water, 56.37 

Caoutchouc 31.70 

Albumen 1 .90 1 

Wax,  a trace - 

An  azotic  body 7.13 

Gummy  body  2.90 

100 

His  analysis  of  caoutchouc  gave 

Carbon, 87.2 

Hydrogen, 12.8 

Thomson  thinks  it  composed  of  an  equal  number  of  atoms  of  carbon  and 
hydrogen. 


Products  of  2179.  By  distillation  at  a low  temperature  and  exposing  the  pro- 
distillation.  ducts  t0  a freezing  mixture,  several  different  liquids  have  been 
obtained  from  caoutchouc.t  These  are  Eupion§  a limpid  liquid  that 
boils  at  124°;  Caoutchene  an  oily  substance  ; Heevene  which  remains 


* Soak  the  common  bags  in  sulphuric  ether,  sp.  gr.  0.763,  at  a temperature  not  less 
than  50°  Fahr.  for  a period  of  time  not  less  than  one  week,  (the  longer  the  better.) 
Empty  the  bag,  wipe  it  dry,  put  into  it  some  dry  powder,  such  as  starch,  insert  a lube 
into  the  neck,  and  fasten  it  by  a broad  soft  band  slightly  applied,  and  then  commence 
by  mouth  or  bellows  the  inflation.  If  the  bag  be  unequal  in  thickness,  restrain  by  the 
hand  the  bulging  of  the  thinner  parts,  until  the  thicker  have  been  made  to  give  way  a 
little.  When  the  bag  has  become  by  such  means  nearly  uniform,  inflate  a little  more, 
shake  up  the  included  starch,  and  let  the  bag  collapse.  Repeatthe  inflations  until  the 
bag  is  sufficiently  distended. 

t From  recent  experiments  Ure  infers  that  albumen  is  not  a necessary  constituent  of 
the  juice.  See  his  new  experiments  in  Philos.  Mag.  July  1839. 

t Bouchardt,  Jour,  de  Pharm . xxiii.  454. 

§ From  the  Greek  ev  well  and  nuov  fatty. 


Paraffin— Eupion,  477 

after  the  volatile  oils  are  distilled  off ; it  is  an  acid  liquid  boiling  at  Sect.  iv. 
600°  and  burning  like  the  volatile  oils  ; and  carburet  of  hy- 
drogen. 

2180.  Extractive.  Most  plants  yield  to  water  a substance  differing  j)ivis-on 
from  any  proximate  principles  of  vegetables,  which  constitutes  apart  9th. 

of  what  is  called  an  extract  in  pharmacy,  and  which  has  been  express-  Extractive, 
ed  by  the  term  extractive.  It  is  always  mixed  with  other  princi- 
ples and  there  is  no  proof  that  it  is  identical  in  different  plants. 

Berzelius  distinguishes  it  by  the  name  of  apotheme  (deposite). 

2181.  Many  vegetable  substances  have  an  intensely  bitter  taste,  Div—on 
and  on  that  account  are  employed  in  medicine,  by  brewers,  &c.  ioth. 
There  appears  to  be  a great  variety  of  bitter  principles,  many  of  Bitter  prim 
which  have  received  distinct  names  derived  from  the  name  of  the  ciples' 
vegetable,  as  quassite  from  Quassia,  gentianite  from  gentian,  eolo- 
cynthite  from  colocynth,  &c. 

2182.  Products  of  the  destructive  distillation  of  vegetable  sub - Division 
stances.  Some  of  these  are  found  in  matters  existing  on  the  earth  ; p^'uctg  of 
but  it  is  probable  that  they  have  been  formed  originally  by  the  destructive 
destructive  distillation  of  vegetables  or  trees,  in  some  great  processes  distillation, 
of  nature. 

2183.  Naphtha.  This  liquid  exudes  from  the  earth  in  Persia  and  Naphtha, 

some  other  countries  ; and  is  obtained  by  distilling  petroleum  and 
asphaltum,  and  by  rectifying  coal  tar.  Naphtha  is  limpid,  and  colour- 
less, like  water  ; it  has  a bituminous  odour,  a sp.  gr.  of  0.817  and  D ' . 
burns  with  much  flame  and  smoke.  Pr0petUeS- 

2184.  It  is  insoluble  in  water,  but  soluble  in  alcohol.  It  softens 
caoutchouc  which  swells  in  it  to  more  than  30  times  its  original  bulk 
and  becomes  gelatinous  and  transparent : by  long  boiling  a solution 
is  effected. 

2185.  Petroleum  is  less  limpid  than  naphtha,  and  unctuous  to  the  petroieum. 
touch.  Asphaltum  is  a solid,  brittle  bitumen  of  a black  colour,  and  Asphaltum. 
vitreous  lustre.  It  is  soluble  in  about  5 times  its  weight  of  naphtha, 

and  the  solution  forms  a good  varnish.  It  is  found  on  the  surface 
and  on  the  banks  of  the  Dead  Sea,  and  in  large  quantities  in  Barba- 
does  and  Trinidad. 

2186.  Among  the  products  of  the  destructive  distillation  of  vege-  Tar  from 
table  and  animal  substances  is  a black  inflammable  liquid  called  tar.  coal. 

A large  quantity  is  formed  during  the  distillation  of  wood  and  the 
preparation  of  coal  gas.  This  tar  has  been  found  to  contain  several 
new  principles  paraffin , eupion , creosote , picamar , capnomor  and 
pittacdl. 

2187.  Paraffin  is  obtained  most  abundantly  from  the  tar  of  the  Paraffin, 
beech  tree.  It  is  a transparent  and  crystalline  substance,  of  a white 
colour,  and  destitute  of  taste  and  smell.  It  melts  at  110°  into  a 
colourless  oil : at  a higher  temperature  it  boils  and  may  be  distilled. 

Its  sp.  gr.  is  0.870. 

2188.  It  has  very  little  tendency  to  combine  with  other  bodies ; 
hence  its  name  paraffin  ( parum  affinis.)  Ether  is  its  best  solvent. 

2189.  Eupion  is  obtained  by  distilling  the  tar  which  is  procured  by  Eupion, 
decomposing  animal  matter  in  the  dry  way.  It  may  also  be  obtained 

from  vegetable  and  coal  tar  ; or  much  purer  from  rapeseed  oil.  The 


478 


Chap.  IX. 
Properties. 

Creosote. 


Properties. 


Solubility, 

&c. 


Coagulates 

albumen. 


Arapalin. 


Organic  Chemistry — Creosote. 

oil  is  distilled  in  an  iron  retort  with  a moderate  fire,  so  that  the  oil 
may  not  pass  over.* 

2190.  It  is  a colourless  liquid,  which  does  not  become  solid  though 
cooled  down  to  — 4°.  It  is  tasteless  but  smells  like  blossoms.  It 
boils  at  116£°.  Its  sp.  gr.  is  0.655.  Absolute  alcohol  dissolves  it. 
Naphthaline,  camphor,  tallow,  and  many  other  substances  dissolve  in 
eupion  ; caoutchouc  swells  enormously  in  it,  and  on  boiling  is  dis- 
solved. 

2191.  Creosote  was  discovered  by  Reichenbach  in  1832.  It  exists 
in  impure  pyroligneous  acid,  but  is  best  prepared  from  those  portions 
of  the  oil  distilled  from  wood-tar  which  are  heavier  than  water. 
The  oil  is  first  freed  from  adhering  acetic  acid  by  carbonate  of  po- 
tassa,  and,  after  separation  from  the  acetate,  is  distilled.  A little 
phosphoric  acid  is  mixed  with  the  product  to  neutralize  ammonia, 
and  another  distillation  resorted  to.  It  is  next  mixed  with  a strong 
solution  of  potassa,  which  combines  with  creosote,  allows  any  eupi- 
on which  may  be  present  to  collect  on  its  surface,  and  by  digestion 
decomposes  other  organic  matter : the  alkaline  solution  is  then 
neutralized  by  sulphuric  acid,  and  the  oil  which  separates  is  collect- 
ed and  distilled.  For  the  complete  purification  of  the  creosote,  this 
treatment  with  potassa,  followed  by  neutralization  and  distillation, 
requires  to  be  frequently  repeated. 

2192.  Creosote  is  a colourless  transparent  liquid  of  an  oily  con- 
sistence, which  retains  its  fluidity  at  — 17°,  has  a sp.  gr.  of  1.037  at 
68°,  boils  at  397°,  is  a non-conductor  of  electricity,  and  refracts 
light  powerfully.  It  has  a burning  taste  followed  by  sweetness,  and 
its  odour  is  like  that  of  wood-smoke  or  rather  of  smoked  meat.  It 
is  highly  antiseptic  to  meat : the  antiseptic  virtue  of  tar,  smoke,  and 
crude  pyroligneous  acid  seems  owing  to  the  presence  of  creosote. 
Its  name,  from  xpsds  Jlesh,  and  oru>£w  I save , was  suggested  by  this 
property. 

2193.  Creosote  requires  about  80  parts  of  water  for  solution,  and 
is  soluble  in  every  proportion  in  alcohol,  ether,  sulphuret  of  carbon, 
eupion,  and  naphtha.  It  has  neither  an  acid  nor  alkaline  reaction 
with  test  paper,  but  combines  both  with  acids  and  alkalies.  With 
potassa,  soda,  lime,  and  baryta  it  forms  compounds  soluble  in  water; 
but  the  creosote  is  separated  even  by  feeble  acids.  Of  the  acids,  it 
unites  most  readily  with  the  acetic,  dissolving  in  every  proportion  : 
by  strong  nitric  and  sulphuric  acid  it  is  decomposed.  Creosote  unites 
also  with  chlorine,  iodine,  bromine,  sulphur,  and  phosphorus. 

2194.  Creosote  acts  powerfully  in  coagulating  albumen,  this  effect 
being  produced  by  a solution  of  one  drop  in  a large  quantity  of  water. 
It  acts  with  energy  on  living  beings.  Insects  and  fish  thrown  into 
the  aqueous  solution  of  creosote  are  killed,  and  plants  die  when 
watered  with  it.  It  appears  useful  in  medicine  ; it  is  said  to  be  very 
efficacious  as  a topical  application  in  tooth  ache,  ulcers,  and  cutaneous 
diseases;  and  it  probably  admits  of  many  other  applications. 

Creosote  is  a compound  of  carbon,  hydrogen,  and  oxygen  ; the 
ratio  of  its  elements  is  C,;H3£0.t  T. 

* For  details  of  the  process  see  T.  Org.  Bodies , 726. 

iAmpelin  was  prepared  by  Laurent  from  the  oil  of  bituminous  slate,  which  boils  at 
392°  and  536.°  (Ann.  de  Chim.  et  de  Phy.  xiv.  326.)  It  is  an  oily  looking  liquid 
soluble  in  water. 


Naphthaline, . 

2195.  Picamar.  This  substance  is  the  bitter  principle  of  tar, 
whence  it  derives  its  name  (in  pice  amarum.)  It  is  present  in  the 
heaviest  portions  of  the  rectified  oil  of  tar,  and  when  these  are  treat- 
ed by  potassa,  a crystalline  compound  of  the  alkali  and  picamar 
is  formed  : this  compound,  when  purified  by  repeated  solution  in 
water  and  crystallization,  is  decomposed  by  phosphoric  acid,  and  the 
picamar  separated  by  distillation. 

2196.  Picamar  is  an  oily  colourless  liquid,  of  a peculiar  odour  and 
very  bitter  taste.  Its  sp.  gr.  is  1.100,  and  it  boils  at  545°,  being  con- 
siderably less  volatile  than  creosote.  It  is  insoluble  in  eupion  and 
sparingly  soluble  in  water ; but  it  dissolves  without  limit  in  alcohol 
and  ether.  It  has  no  action  on  test  paper  ; but  it  unites  with  potassa 
as  above  mentioned,  and  strong  sulphuric  acid  dissolves  it  without 
decomposition.  From  its  permanence  in  the  air,  its  fixity  when 
heated,  and  its  oily  nature,  it  is  well  adapted  for  greasing  machinery 
and  protecting  it  from  rust. 

2197.  Pittacal.  When  the  heavy  oil  of  tar  is  digested  with  a so- 
lution of  baryta,  a fine  blue  colour  appears,  which  is  due  to  pittacal, 
from  TUTTa  pitch , and  xallog  ornament . It  is  a solid  of  a beautiful 
blue  colour,  which  admits  of  being  fixed  as  a dye.  It  is  very  perma- 
nent, contains  nitrogen  as  one  of  its  elements,  and  appears  to  belong 
to  the  same  class  of  bodies  as  indigo. 

2198.  Capnomor.  This  substance  occurs  along  with  creosote,  pi- 
camar, and  pittacal  in  the  heavy  oil  of  tar.  On  digesting  that  oil 
with  solution  of  potassa,  the  three  latter  principles  are  dissolved,  and 
the  capnomor  collects  on  the  surface,  combined  with  a little  eupion. 
The  capnomor  is  then  dissolved  by  sulphuric  acid,  in  which  eupion 
is  insoluble ; and  from  the  solution,  on  being  neutralized  with  carbo- 
nate of  potassa,  capnomor  separates,  and  is  purified  by  distillation. 
Its  name  is  derived  from  xanvog  smoke , and  polga  part,  because  it  is 
one  of  the  ingredients  of  smoke. 

2199.  Capnomor  is  a colourless  transparent  liquid,  of  a pungent 
taste  and  rather  pleasant  odour,  has  a sp.  gr.  of  0.975,  and  refracts 
light  almost  as  powerfully  as  creosote.  It  boils  at  365°.  It  is  inso- 
luble in  water  and  solution  of  potassa,  and  is  soluble  in  alcohol,  ether, 
and  eupion.  It  has  the  property  of  dissolving  caoutchouc,  espe- 
cially when  heated,  and  is  the  only  ingredient  of  tar  which  does  so  : 
its  presence  in  coal  naphtha  is  the  cause  of  the  solvent  action  of  that 
liquid  on  caoutchouc.  The  composition  of  capnomor  has  not  been 
ascertained,  though  doubtless  carbon  and  hydrogen  are  its  principal 
ingredients,  t.  5.  From  its  being  decomposed  by  nitric  acid  Thomson 
is  inclined  to  suspect  that  it  contains  oxygen. 

2200.  Cedriret  has  been  still  more  recently  obtained  by  Reichen- 
bach  from  the  rectified  oil  of  the  tar  of  beech  wood.  It  strikes  a red 
colour  with  persulphate  of  iron,  and  all  substances  that  easily  part 
with  oxygen  ; even  the  oxygen  of  the  air  renders  the  liquid  red.  It 
forms  red  crystals  which  lie  upon  the  filter,  entangled  in  each  other 
like  a net,  hence  the  name  from  cedrium  an  old  name  for  the  sour 
water  of  tar  burners , and  rete  a net. 

2201 . Naphthaline.  C10H4  = 64  eq.  This  substance  was  discovered 
in  1819  in  one  of  the  condensing  vessels  erected  in  London  for  the 


479 


Sect.  IV. 


Picamar. 


Properties. 


Pittacal. 


Capnomor. 


Properties. 


Cedriret. 


Naphtha- 

line. 


r 


480 


Chap.  IX. 


Obtained. 


Properties. 


Action  of 
chlorine. 


Nitronaph- 

thaiese. 


In  oil  and 
coal  gases. 


Coal  gas 
obtained. 


NAphlhAlic 

acid. 


Organic  Chemistry — Coal  Gas. 

distillation  of  coal  tar.*  It  was  named  from  its  connexion  with  coal 
naphtha. 

2202.  When  coal  is  heated  in  iron  retorts,  for  the  preparation  of 
coal  gas,  much  brown  semi-fluid  matter  is  obtained  called  coal  tar. 
It  is  from  this  tar  that  coal  naphtha  and  naphthaline  are  procured. 
To  obtain  the  latter  the  tar  is  distilled. 

The  first  fourth  that  comes  over  is  partly  naphtha,  with  water  holding  ammo- 
nia and  naphthaline  in  solution.  The  next  fourth  part  is  a dense  oil  mixed  with 
naphthaline,  the  latter  increases  in  quantity  as  the  distillation  proceeds.  From 
the  last  portions  distilled  the  naphthaline  crystallizes  and  may  be  freed  from  the 
oil  by  pressure  between  folds  of  blotting  paper  and  then  subliming  at  a gentle 
heat.t 

2203.  Naphthaline  is  white  and  of  a pearly  lustre.  Its  smell  is 
aromatic,  its  taste  pungent.  It  evaporates  spontaneously.  It  melts 
at  174°  and  boils  at  4 10°. I With  sulphuric  acid  it  forms  sulpho- 
naphthalic  acid. 

2204.  Chlorine  and  bromine  act  with  violence  on  naphthaline, 
heat  is  disengaged  and  hydrochloric  and  hydrobromic  acids  are 
formed.  It  is  composed  of  10  atoms  carbon  and  4 hydrogen  = 65.2. 

2205.  When  nitric  acid  and  naphthaline  are  left  in  contact  at  com- 
mon temperatures  no  action  takes  place.  But  if  the  acid  is  boiled, 
red  vapours  are  emitted  and  an  oily  layer  collects  on  the  surface, 
which  affords  two  products  : one  solid,  which  is  nitronaphthalese,  the 
other  a liquid  separable  by  bibulous  paper. 

Another  substance  obtained  from  coal  tar  is  paranaphthaline , so 
named  by  Dumas  from  its  composition  being  the  same  as  that  of 
naphthaline.^ 

2206.  In  the  coal  and  oil  gases  prepared  for  ordinary  combustion, 
small  portions  of  several  of  the  foregoing  substances  are  believed  to 
be  present,  communicating  their  peculiar  properties  and  improving 
the  brilliancy  of  the  light. 

The  distillation  of  coal  is  conducted  in  oblong  cast-iron  cylinders,  or  retorts, 
which  arc  ranged  in  furnaces  to  keep  them  at  a red  heat,  and  all  the  volatile 
products  are  conveyed  by  a common  tube  into  a condensing  vessel , kept  cold  by 
immersiou  in  water  ; and  in  which  the  water,  tar,  ammoniacal,  and  other  con- 
densable vapours,  are  retained  ; the  gaseous  products  consist  principally  of  carbu- 
retted  hydrogen,  hydrosulphuric  acid  gas,  carbonic  oxide  and  acid  ; these  are 
passed  through  a mixture  of  quicklime  and  water  in  vessels  called  purifiers , by 
which  the  hydrosulphuric  acid  and  carbonic  gases  are  absorbed,  and  the  carburet- 
ted  hydrogen  and  hydrogen  gases,  transmitted  sufficiently  pure  for  use  in  to  gaso- 
emters , whence  the  pipes  issue  for  the  supply  of  streets,  houses,  &c.  The  coke 
remaining  in  the  retorts  is  of  a very  good  quality. || 


* Ann.  Philos,  xv.  74,  vi.  N.  S.  135,  and  Phil.  7 Vans.  1821,  209. 
t Reichenbach  has  endeavoured  to  prove  that  naphthaline  does  not  exist  ready 
formed  in  coal-tar,  but  that  it  is  formed  when  the  oil  existing  in  this  tar  is  exposed  to 
a high  temperature,  but  this  was  not  confirmed  by  the  experiments  of  Laurent,  for 
which  see  T.  Org.  Bodies,  738.  t413£°,  Dumas. 

5 Naphthalic  Acid.  C10H2O4.  This  acid  has  great  resemblance  to  benzoic  ; it  is 
white,  when  pure,  and  crystallizes  in  long  feathery  crystals.  It  melts  at  212°  and 
may  he  volatilized  without  decomposition.  Its  fumes  readily  take  fire.  It  has  no 
smell,  and  a weak  taste.  While  ary  it  does  not  affect  litmus  paper,  but  reddens  it 
if  moistened.  It  combines  with  bases  and  forms  naphthalates.  The  greater  number 
of  these  when  heated  elongate  to  a great  extent  under  the  form  of  a black  glass,  at- 
tended with  the  disengagement  of  a peculiar  crystallizable  matter. 

This  acid  belongs  to  the  volatile  acids  of  Thomson  (Org.  Bodies,  27)  to  whose  de- 
scription the  reader  is  referred  for  details  and  for  an  account  of  its  compounds. 

||  For  a full  account  of  the  process,  see  Ure’s  Diet.  Arts  and  Afanuf.  545. 


Animal  Charcoal  481 

2207.  The  best  kind  of  coal  for  distillation  is  that  which  contains  Sect,  iv, 
most  bitumen  and  least  sulphur  ; 112  pounds  of  good  coal  are  capa- 
ble of  yielding  from  450  to  500  cubic  feet  of  gas  of  such  quality,  that 

half  a cubic  foot  per  hour  is  equivalent  to  a mould  candle  of  six  to 
the  pound,  burning  the  same  space  of  time.  H.  The  sp.  gr.  of  the  gas 
varies,  the  mean  as  given  by  Ure  is  0.529  and  that  of  oil  gas 
0.96.* 

2208.  The  apparatus  for  the  conversion  of  oil  into  gas  consists  of  Oil  Sas- 
a furnace  with  a contorted  iron  tube  containing  fragments  of  bricks  or 
coke,  passing  through  it,  into  which, when  red-hot,  the  oil  is  suffered  to 

drop ; it  is  decomposed,  and  converted  almost  entirely  into  charcoal, 
which  is  deposited  in  the  tube,  and  into  a mixture  of  carburetted  hy- 
drogen, and  hydrogen  gases,  of  which  one  volume  may  be  regarded 
as  equivalent  to  two  of  coal-gas,  for  the  production  of  light.! 

The  commonest  whale  oil,  quite  unfit  for  burning  in  the  usual 
way,  affords  abundance  of  excellent  gas,  requiring  no  other  purifica- 
tion than  passing  through  a refrigerator  to  free  it  from  a quantity  of 
empyreumatic  vapour.  A gallon  of  whale-oil  affords  about  100  cubi- 
cal feet  of  gas. 

2209.  Lamp-black  is  prepared  from  the  refuse  of  resin  collected  in  , 
the  distillation  of  oil  of  turpentine.  It  is  a fine  black  powder,  ex-  black, 
ceedingly  light.  The  soot  which  collects  in  chimneys  where  coal  or 
wood  is  burnt  differs  from  lamp-black.  When  boiled  with  water  a 
matter  is  deposited  of  the  appearance  of  pitch;  alcohol  and  ether  re- 
move a portion  of  an  exceedingly  acrid  and  bitter  taste,  which  Bra- 
connot  has  called  asbolin,  from  ckjGoXt]  soot ; it  is  fluid  and  not 
volatile. 

2210.  Animal  charcoal,  though  derived  from  the  animal  kingdom,  Animal 
is  supposed  to  owe  its  most  important  properties  to  the  charcoal  charcoal, 
which  it  contains.  It  is  known  as  ivory  black  and  is  prepared  from 


* The  illuminating  power  of  different  gases  burned  in  the  same  circumstances,  is  muminating 
proportional,  generally  speaking,  to  their  sp.  gr.  as  this  is  to  the  quantity  of  carbon  power  of  can- 
they  contain.  A mould  tallow  candie  of  6 in  the  pound,  burning  for  an  hour,  is  equi-  dle®  andlamP*- 
valent  to  half  a cubic  foot  of  ordinary  coal  gas,  aud  to  four  tenths  of  a foot  of  good  gas. 

The  flame  of  the  best  Argand  lamp  of  Carcel,  in  which  a steady  supply  of  oil  is  main- 
tained by  pump-work,  consuming  649  grains  in  an  hour,  and  equal  to  9-38  such  candles, 
is  equivalent  to  3.75  cubic  feet  of  coal  gas  per  hour.  A common  Argand  lamp,  equal 
to  4 candles,  consumes  463  grains  per  hour,  and  is  represented  by  1.6  cubic  feet  of 
gas.  Ure. 

t The  cut  (Fig.  197)  represents  an  apparatus  contrived  by  me, 
and  which  is  very  convenient  for  obtaining  oil  gas,  in  sufficient 
quantity  for  the  exhibition  of  its  properties  ; a is  a vessel  of  cast 
iron  about  1 6 inches  in  depth,  and  5 in  diameter  at  its  upper  part ; 
having  a cast  iron  cover,  with  two  openings,  to  the  smallest  of 
which,  a copper  pipe  leading  from  a funnel-shaped  oil  vessel  b,  is 
secured  by  brazing;  into  the  larger  opening  a gun-barrel  c is 
screwed  which  enters  a small  copper  condensing  vessel  d fur- 
nished with  a cock  for  drawing  on  any  oil,  or  condensable  va- 
pours that  may  pass  over.  From  the  upper  part  of  the  condenser 
a copper  or  lead  pipe  issues,  whic;h  conveys  the  gas  to  the  gaso- 
meter. When  oil  gas  is  to  be  obtained,  the  vessel  b is  filled 
with  oil,  and  the  pieces  of  bricks  are  put  into  the  retort  a,  the 
cover  is  then  secured  by  a rod  of  iron  passing  through  the  ears 
ee,  and  the  joint  is  made  tight  by  a mixture  of  about  2 parts  of 
sal  ammoniac,  l of  sulphur  and  30  of  cast  iron  filings  or  borings, 
made  into  a paste  with  water.*  This  retort  may  be  placed  in  any 
convenient  furnace,  and  when  heated  to  redness  the  cocky  is  turned  so  as  to  allow 
the  oil  to  pass  drop  by  drop.  W. 

* This  cement  should  be  allowed  to  become  hard  before  the  apparatus  is  mead. 

61 


Oil  gas  appara- 
tus. 


482 


Of  the  Parts  of  Plants . 


Chap.  IX, 


Uses. 


Sup  of 
plants. 


Changes  of, 


Peculiar 

juices. 


Gum  resin. 


Air  in 
plants. 


Bark. 


Neutral  com- 
pound* con- 
taiaiog  aitro- 
C*d. 


the  bones  of  animals  which  are  heated  in  close  vessels,  so  as  to  drive 
off  all  the  volatile  matter.  The  earth  of  bones  remains  mixed  with 
charcoal.  Being  reduced  to  powder  it  is  fit  for  use. 

2211.  It  is  a much  more  powerful  discolourizing  principle  than  ve- 
getable charcoal.  It  is  much  employed  in  refining  sugar.  When 
used  to  remove  the  colour  of  liquids,  it  acts  much  better  if  the  liquid 
be  slightly  acid  or  neutral,  and  at  a boiling  temperature.  It  appears 
to  act  chemically  upon  the  colouring  matter.* 


Section  V.  Of  the  Parts  of  Plants. 

2212.  It  is  the  general  opinion  that  plants  receive  a considerable 

part  of  their  nourishment  by  the  root ; that  it  enters  them  in  a liquid 
state,  and  passes  up  in  proper  vessels  towards  the  leaves.  This 
liquid  is  distinguished  by  the  name  of  sap.  In  nearly  all  vegetables 
it  is  as  liquid  as  water.  It  always  contains  an  acid,  sometimes  free, 
but  more  commonly  combined  with  lime  and  potassa.  Various  ve- 
getable principles  are  also  present;  of  these  sugar  is  the  most 
remarkable,  and  mucilage.  Sometimes  albumen  and  gluten,  and 
tannin  can  be  detected.  When  left  to  itself,  sap  soon  effervesces  and 
becomes  sour  ; or  even  vinous,  when  the  proportion  of  sugar  is  con- 
siderable. X j, 

2213.  In  its  passage  to  the  leaves  the  sap  is  altered  by  a process 
similar  to  that  of  digestion  in  animals,  and  formed  into  all  the  liquid 
substances  required  for  the  purposes  of  the  plant.  These  liquids 
flow  from  the  leaves  towards  the  root  in  appropriate  vessels,  and 
have  received  the  name  of  the  peculiar  juices  of  vegetables.  They  j* 
differ  in  different  plants.  They  always  contain  much  more  vegeta- 
ble matter  than  the  sap.  Sometimes  they  exude  spontaneously  and 
may  always  be  procured  by  incisions  through  the  bark. 

2214.  The  milky  juices  concrete  into  a solid  matter  which  has 
been  called  gum  resin.  Several  of  the  gum  resins  are  employed  in 
medicine  ; the  most  important  of  which  is  the  juice  of  the  poppy  af- 
fording opium. 

2215.  In  many  plants  the  stem  is  hollow  and  filled  with  air ; in 

some,  as  the  onion,  it  is  contained  in  the  leaves  ; it  is  lodged  in  the  r: 

pod  of  the  pea,  and  in  the  leaves  of  some  species  of  fuci.  In  some  a 

plants  the  proportion  of  oxygen  in  this  air  is  greater  than  in  common 
air,t  and  others  contain  more  nitrogen  ; but  generally  so  far  as  expe- 
riments have  been  made  it  is  common  air  unaltered. 

2216.  The  bark  is  composed  of  three  distinct  portions  ; the  outer- 
most or  epidermis,  the  parenchyma,  and  that  next  the  wood  the  cor- 
tical layers.  The  latter  consist  of  several  thin  membranes,  composed 
of  fibres  forming  a kind  of  net-work. 


* See  Bussy’s  experiments,  T.  Org.  Bodies,  756,  and  Jour,  de  Pharrn.  v iii.  257. 
There  are  several  substances  obtained  from  plants  by  processes  similar  to  those 
employed  for  obtaining  the  vegetable  alkalies,  which  have  been  arranged  together  by 
Thomson.  They  are  caffein  from  coffee,  piperin  from  pepper,  daphnin  from  daphne 
alpina  and  mezerium,  jalappin  from  jalap,  sinapin  from  mustard,  hesperidin  from  the 
unripe  orange  and  lemon,  populin  and  plumbagin.  For  details  see  T.  *>rg.  Bod.  757. 
t Priestley,  iii.  279. 


Wood* * * §— Cotton. 


483 


2217.  The  substance  known  as  cordis  the  epidermis  of  the  quercus  Sect,  v. 
tuber,  which  contains  a peculiar  principle  called  suberin.  Three  Cork. 

[different  kinds  of  cinchona  bark  were  early  distinguished,  the  pale, 
red  and  yellow.  The  first  is  the  bark  of  the  cinchona  lancifolia , the 
Isecond  of  the  c.  oblongifolia,  and  the  last  of  the  c.  cordifolia .* 

2218.  The  roots  of  a great  variety  of  plants  are  employed  in  me-  Roots, 
ilicineand  the  arts.  The  substances  found  in  them  are  various  ; 

and  indeed,  as  the  peculiar  juices  of  the  roots  are  always  included  in 
! such  examinations,  it  is  clear  that  almost  all  the  vegetable  principles 
] will  be  found  in  them.  t. 

2219.  Bulbs  are  composed  of  concentric  coats  like  the  onion,  or  Bulbs, 
i are  imbricated.  Several  of  them  are  used  as  nutritive  articles  of 

food,  and  some  constitute  active  medicines. 

Squill,  the  bulbous  root  of  the  scilla  maritima , owes  its  peculiar  Squill, 
properties  to  a species  of  bitter  principle  which  has  been  called 
scilitin. 

Potatoes  are  the  bulbs  of  the  solanum  tuberosum,  an  American  Potatoes, 
plant,  said  to  grow  wild  in  Peru  and  Chili.  According  to  Einhof 
potatoes  afford 


Starch 

Fibrous  matter 

Albumen 

Mucilage 


15t 

7 

1.4 

4 

27.4 


They  afforded  also  a mixture  of  tartaric  and  phosphoric  acids. 


When  potatoes  are  exposed  to  the  action  of  frost,  they  acquire  a Action  of 
sweet  taste,  followed  by  an  acid  taste,  owing  to  the  rapid  evolution  of  frost  upon, 
acetic  acid,  and  the  root  soon  putrefies.  The  sugar  is  formed  at  the 
expense  of  the  mucilage.  Potatoes  differ  from  wheat  and  barley  by 
containing  no  gluten. 

2220.  Woods.  The  mere  woody  fibres  of  all  plants  are  probably  Woods, 
nearly  the  same,  and  the  differences  are  owing  to  the  various  propor- 
tions of  liquids  and  empty  spaces  with  which  the  woody  fibres  are 
intermixed.!  The  vegetable  fibres  in  herbaceous  plants  correspond 

to  the  wood  of  trees.  In  some  it  is  flexible  and  tough,  as  in 
hemp,  nettles,  &c.§ 

2221.  Cotton  is  a soft  down  which  envelopes  the  seeds  of  various  Cotton, 
species  of  gossypium.  It  has  q.  strong  affinity  for  some  of  the  earths, 
especially  alumina ; hence  this  substance  is  used  to  fix  colours  on 
cotton  ; the  cloth  is  steeped  in  a solution  of  alum  or  acetate  of  alu- 
mina, and  afterwards  dyed.  Several  of  the  metallic  oxides  also 
combine  with  it  readily,  of  which  oxide  of  iron  is  one  of  the  most  re- 
markable. Oxide  of  tin  also  combines  with  it  and  is  used  as  a mor- 
dant. 

2222.  Cotton  combines  readily  with  tannin  and  forms  a yellow  or 
brown  compound.  Hence  infusion  of  galls,  and  of  other  astringent 
substances  is  often  used  as  a mordant  for  cotton. 


* The  bark  from  which  quinia  is  extracted  in  France,  is  called  quinquina  calisaya  ; 
but  the  species  of  cinchona  to  which  it  belongs  does  not  seem  yet  accurately  known.  T, 

t For  table  of  the  quantity  of  starch  from  different  kinds  of  potatoes,  see  T.  Org » 
Bodies,  841. 

t For  a table  of  the  results  of  the  analysis  of  various  woods  see  T.  Org.  Bodies , 849, 

§ Perhaps  the  fibres  ought  to  be  considered  rather  as  the  libtr  or  inner  bark. 


484 


Chap.  IX 

Quantity 
of  oxygen 
required  lor 
combustion 
of  woods. 


Senna. 


Night- 

shade. 


Hemlock. 


Flowers. 


/ 


Colouring 

matter. 


Of  the  Part$  of  P huts. 


2223.  The  quantity  of  oxygen  required  for  burning  100  parts  of 
various  kinds  of  wood  has  been  made  the  subject  of  experiments 
which  are  important,  as  this  oxygen  is  proportionable  to  the  quan- 
tity of  heat  evolved  by  each. 


100  parts  of  Tilia  Europea,  lime  require 
Ulmus  suberosa,  elm  “ 
Pinus  abies,^r  M 

“ larix,  larch  u 
Acer  campe6tris,Tnfl^Ze  “ 
Pinus  picea,  pitch-pine  “ 
Juglans  regia,  walnut  “ 
Quercus  robur,  oak  M 
Betula  alba,  birch  “ 


140.523 
139.408 
138.377 
, 138.082 

136.960 
136.886 
135.690 
133  472 
133.229* 


2224.  Leaves.  Senna.  According  to  Lagrange  the  leaves  of  the 
Cassia  senna  are  characterized  by  containing  a peculiar  extractive 
principle,  cathartina , which,  by  long  boiling,  passes  into  a resinous 
substance,  in  consequence  of  absorbing  oxygen  ; they  also  contain 
a resin  which  resists  the  action  of  water,  and  is  soluble  in  alcohol; 
the  whole  of  the  soluble  matter  amounts  to  about  one  third  the  weight 
of  the  senna.t 

2225.  Nightshade.  The  leaves  of  the  Atropa  Belladonna  con- 
tain, according  to  Vauquelin, 


1.  Vegetable  albumen,  or  gluten. 

2.  A bittor  narcotic  princi{He. 

3.  Nitrate,  muriate,  sulphate,  binoxalate,  and  acetate  of  potassa. 

Brandes  announced  the  existence  of  a new  vegetable  alkali  in  this 

plant,  which  he  calls  atropia.  It  forms  brilliant  acicular  crystals, 
tasteless,  and  difficultly  soluble  tn  water  and  alcohol. 

2226.  Hemlock , conium  maculatum.  This  plant  was  formerly 
called  cicuta ; it  contains  a peculiar  principle  conicina , and  its  juice 
in  chemical  composition  has  a striking  similarity  to  that  of  the  cab- 
bage. 

2227.  Flowers.  The  colouring  matter  of  most  flowers  is  extremely 
fugitive,  and  is  generally  much  changed  by  mere  exsiccation.  They 
usually  communicate  their  colour  to  water;  the  infusion  of  blue 
flowers  is  generally  reddened  by  acids,  and  changed  to  green  or  yel- 
low by  alkalies  ; that  of  yellow  flowers  is  made  paler  by  acids,  and 
alkalies  render  it  brown  ; the  red  infusion  of  many  flowers  is  exalted 
in  tint  by  acids,  and  changed  to  purple,  and  in  some  instances,  to 
green,  by  alkalies. 

It  is  probable  that  one  and  the  same  principle  gives  colour  to  seve- 
ral of  the  blue  and  red  flowers,  but  that  the  presence  of  acid  in  the 
latter  produces  the  red  ; the  petals  of  the  red  rose,  triturated  with  a 
little  carbonate  of  lime  and  water,  give  a blue  liquor  ; alkalies  render 
it  green,  and  acids  restore  the  red. 

2228.  A colouring  matter  analogous  to  that  of  the  violet,  exists  in 
the  petals  of  red  clover,  in  the  red  tips  of  those  of  the  common  daisy, 
of  the  blue  hyacinth,  the  holly-hock,  lavender,  in  the  inner  leaves  of 
the  artichoke,  and  in  numerous  other  flowers  ; reddened  by  an  acid, 
it  colours  the  skin  of  several  plums,  and  the  petals  of  the  scarlet  ge- 


* Ann.  de  Pharm.  xvii.  144. 

t In  the  Lond.  Med.  Repot,  rol.  xv.  ^69,  the  effect*  of  the  various  re  agents  on  in» 
fusion  of  senna  are  detailed  by  Batlay.  • 


485 


Seeds-— Coffee 


ranium  and  pomegranate.  Some  flowers  which  are  red,  become  s«ct.  v- 
blue  by  merely  bruising  them  ; this  is  also  the  case  with  the  colour- 
ing matter  of  red  cabbage  leaves,  and  of  the  rind  of  the  long  radish. 

Smithson  has  suggested  that  the  reddening  acid  is  in  these  cases  the 
carbonic,  which  escapes  on  the  rupture  of  the  vessels  which  inclose 
it. 

2229.  The  petals  of  the  common  corn-poppy , rubbed  upon  paper, 
give  a purple  stain,  little  altered  by  ammonia,  or  carbonate  of  soda, 
but  made  green  by  caustic  potassa.  The  infusion  of  poppy-petals  in 
very  dilute  hydrochloric  acid,  is  florid  red  ; chalk  added,  renders  it  of 
the  colour  of  port  wine ; carbonate  of  soda  in  excess  gives  the  same 
colour,  but  excess  of  potassa  changes  it  to  green  and  yellow.  The 
expressed  juice  of  the  black  mulberry  possesses  nearly  the  same  pro- 
perties.^ 

2230.  Seeds.  Starch  is  an  essential  component  of  the  greater  Se«ds. 
number  of  seeds,  and  it  is  generally  united  in  them  with  a variable 
portion  of  gluten,  and  often  of  fixed  and  of  volatile  oil. 

Davy  examined  a number  of  seeds  with  a view  to  determine  their 
relative  nutritive  powers:  for  the  results  of  his  experiments  see  Ag- 
ricultural Chemistry,  4to.  131. 

2231.  Almonds,  the  seeds  of  the  amygdalus  communis,  consist  of  Almonds, 
an  albuminous  substance  and  oil ; the  latter  may  be  obtained  by  ex- 
pression, five  pounds  yielding  about  one  pound  of  cold  drawn  oil,  and 

about  a pound  and  a half  when  aided  by  heat.  The  bitter  almond 
affords  by  pressure  an  oil  analogous  to  that  from  the  former ; but  if 
the  expressed  cake  be  distilled  with  water,  a portion  of  volatile  oil 
eminently  poisonous,  and  smelling  strongly  of  the  almond,  is  ob- 
tained ; this  oil  is  used  as  a flavouring  material  by  confectioners,  and 
by  the  manufacturers  of  noyeau.f 

2232.  Colocynth.  The  pulp  of  the  fruit  of  the  cucumis  colocynthis  Colocynth. 
or  bitter  cucumber  is  much  used  in  medicine  under  the  name  colo- 
quintida.  It  contains  a peculiar  bitter  principle  colocynthin. 

2233.  Elaterium  is  deposited  from  an  infusion  of  the  fruit  of  the  Elaterium. 
momordica  elaterium  or  wild  cucumber.  The  active  principle  has 

been  obtained  by  Paris  and  Faraday  and  named  elatin.X 

2234.  Coffee,  the  seed  of  the  Coffea  Arabica  has  been  examined  Coffee, 
both  in  its  raw  and  roasted  state. 

Hermann  has  given  the  following  comparative  analysis  of  coffee 
from  the  Levant  and  from  Martinique, § the  results  of  which  differ 
much  from  those  of  Cadet: 


Resin 

Levant. 

74 

. 

Martinique . 
68 

Extractive 

320 

- 

- 310 

Gum 

130 

- 

- 144 

Fibrous  matter  « 

- 1335 

- 

- 1386 

Loss  - - - * - 

61 

- 

12 

1920 

1920 

When  coffee  is  roasted  it  undergoes  a peculiar  change  of  compo- 


* Smithson,  Phil.  Trans.  1818,  110. 

tin  the  Phil.  Trans,  for  1811,  Brodie  has  detailed  a variety  of  experiments  illus- 
trative of  its  action  as  a poison. 

I Paris’  Pharmacol.  4th  edit.  Sf8.  % C roll’s  Annales , 


486 


('hap  IX. 


Mustard. 


Lupuliu. 


Citisin. 


Fruits  con- 
tain acid, 


And  sugar. 


Colouring 

matter. 


Sap  green. 


Colouring  Matter  of  Fruits . 

sition  attended  by  the  formation  of  tannin,  and  a volatile,  fragrant,  and 
aromatic  principle  ; but  in  this  state  it  has  not  been  examined  with 
any  precision.  It  is  developed  also  by  roasting  barley,  beans  and 
various  vegetables,  which  are  on  that  account  occasionally  employed 
as  substitutes  for  coffee.  Robiquet  discovered  in  coffee  the  principle 
called  caffein. 

2235.  Mustard.  The  seed  of  the  sinapis  nigra  derives  its  acri- 
mony from  volatile  oil ; it  also  contains  a tasteless  fixed  oil,  albumen, 
gum,  and  traces  of  sulphur  and  earthy  salts. 

2236.  Lupulin  was  discovered  by  Ives*  and  Payen  and  Cheva- 
lier, about  the  same  time,  in  the  leaves  of  the  Humulus  lupulus  or 
common  hop.  It  is  extremely  bitter,  of  a yellow  colour,  and  has  an 
aromatic  odour.  It  is  the  principle  on  which  the  characteristic  pro- 
perties of  the  hop  depend. 

2237.  Citisin  was  discovered  by  Payen  and  Chevalier  in  the 
seeds  of  the  Cj/tisus  Laburnum.  Its  colour  is  yellow,  and  it  has  a 
disagreeable  taste  ; it  is  soluble  in  water,  alcohol  and  ether.  It  is 
easily  decomposed  by  heat,  and  the  strong  acids  produce  the  same 
effect. 

2238.  Fruits.  The  acid  matter  contained  in  fruits  is  either  the 
tartaric,  oxalic,  citric,  or  malic;  or  a mixture  of  two  or  more  of 
them  ; but  the  nature  and  proportion  of  the  acid  varies  at  different 
periods  of  their  growth  ; gluten  and  starch  are  found  in  some  fruits, 
and  a gelatinizing  substance,  which  has  sometimes  been  regarded  as 
identical  with  animal  jelly,  but  which  is  probably  a compound  of 
gum  and  one  or  more  vegetable  acids. 

2239.  Most  of  our  common  fruits  also  contain  sugar,  and  it  exists 
in  all  those  the  juice  of  which  is  susceptible  of  vinous  fermentation. 
In  some  fruits  the  quantity  of  sugar  is  increased  by  mashing  and 
exposure  to  air;  this  is  remarkably  the  case  with  some  of  the  rough- 
flavoured  apples  used  for  cider,  the  pulp  of  which  becomes  brown, 
and  at  the  same  time  sweet  by  a few  hours*  exposure. 

2240.  The  colouring  matter  of  fruits  seems  in  most  cases  to  bear 
a strong  resemblance  to  that  of  flowers.  The  red  juice  of  the 
mulberry  was  found  to  exhibit  the  same  characters  as  the  colouring 
principle  of  the  wild  poppy  ; carbonated  alkalies  render  it  blue,  but 
caustic  potassa  changes  it  to  green  and  yellow  : the  juice  of  red 
currants,  cherries,  elder-berries,  and  privet-berries,  and  the  skin 
of  the  buckthorn  berry,  appear  to  contain  a similar  colouring  prin- 
ciple. 

2241.  The  unripe  berries  of  the  buckthorn  furnish  a juice,  which, 
when  inspissated,  is  known  under  the  name  of  sap  green.  It  is 
soluble  in  water,  and  rendered  yellow  by  carbonate  of  soda  and 
caustic  potassa  ; the  acids  redden  it,  and  carbonate  of  lime  restores 
it  to  green,  which  is  therefore  probably  the  proper  colour  of  the 
substance. t 


* Amer.  Jour.  ii> 


t Smithson,  Phil.  Trans.  181 S,  p.  116. 


Fermentation* 


487 


Section  VI.  Phenomena  and  Products  of  Fermentation. 


Sect.  VI. 


Malt. 


Beer. 


2242.  The  term  fermentation  is  employed  to  signify  the  sponta-  t^menta* 
neous  changes,  which  certain  vegetable  solutions  undergo,  placed 

under  certain  circumstances,  and  which  terminate  either  in  the  pro-  Vinousan(i 
duction  of  an  intoxicating  liquor,  or  of  vinegar ; the  former  termi-  acetous, 
nation  constituting  vinous , the  latter  acetous  fermentation. 

The  principal  substance  concerned  in  vinous  fermentation  is  su- 
gar ; and  no  vegetable  juice  can  be  made  to  undergo  the  process, 
which  does  not  contain  it  in  a very  sensible  quantity.  In  the  pro- 
duction of  beer,  the  sugar  is  derived  from  the  malt ; in  that  of  wine, 
frpm  the  juice  of  the  grape. 

2243.  Malt  is  barley  which  has  been  made  to  germinate  to  a cer- 
tain extent,  after  which  the  process  is  stopped  by  heat.  The  barley 
is  steeped  in  cold  water,  and  is  then  made  into  a heap  or  couch,  upon 
the  maltfloor  ; here  it  absorbs  oxygen  and  evolves  carbonic  acid  ; its 
temperature  augments,  and  then  it  is  occasionally  turned  to  prevent  its 
becoming  too  warm.  In  this  process  the  radicle  lengthens,  and  the 
plume  called  by  the  maltsters  the  acrospire , elongates  ; and  when  it 
has  nearly  reached  the  opposite  extremity  of  the  seed,  its  further 
growth  is  arrested  by  drying  at  a temperature  slowly  elevated  to 
150°  or  more.  The  malt  is  then  cleansed  of  the  rootlets. 

2244.  In  the  manufacture  of  beer , the  malt  is  ground  and  infused  in  the  masli- 
tun , in  rather  more  than  its  bulk  of  water,  of  the  temperature  of  160°  or  180°. 

Here  the  mixture  is  stirred  for  a few  hours;  the  liquor  is  then  run  off,  and  more 
water  added,  until  the  malt  is  exhausted.  These  infusions  are  called  wort , and 
its  principal  contents  are  saccharine  matter , starch , mucilage , and  a small  quanti-  Wort, 
ty  of  gluten.  The  strength  of  the  wort  is  adjusted  by  its  specific  gravity,  which 
is  usually  found  by  an  instrument,  not  quite  correctly  called  a saccharometer , 
since  it  is  influenced  by  all  the  contents  of  the  wort,  and  not  by  the  sugar  only.* 

The  wort  is  next  boiled  with  hops,  amounting  upon  the  average,  to  20  dhe 
weight  of  the  malt,  their  use  being  to  cover  the  sweetness  of  the  liquor  by  their 
aromatic  bitter,  and  to  diminish  its  tendency  to  acidify.  The  liquor  is  then 
thrown  into  large,  but  very  shallow,  vessels,  or  coolers,  where  it  is  cooled  to 
about  50°,  as  quickly  as  possible ; it  is  then  suffered  to  run  into  the  fermenting 
vat , having  been  mixed  with  a proper  quantity  of  yeast.  (See  Addenda  ) 

2245.  In  the  fermenting  vessel,  the  different  sub- 
stances held  in  solution  in  the  liquor  begin  to  act  upon 
each  other ; an  intestine  motion  ensues,  the  temperature 
of  the  liquor  increases,  carbonic  acid  escapes  in  large  quan- 
tities ; at  length  this  evolution  of  gas  ceases,  the  liquor 
becomes  quiet  and  clear,  and  it  has  now  lost  much  of  its 
sweetness,  has  diminished  in  specific  gravity,  acquired 
a new  flavour,  and  become  intoxicating.! 


* It  is  a brass  instrument,  of  the  shape  shovvn  in  fig.  198,  so  adjust- 
ed in  weight  as  to  sink  to  the  point  marked  0°,  in  distilled  water,  at  the 
temperature  of  70°,  and  when  immersed  in  a liquor  of  ihe  same  tem- 
perature, and  of  the  specific  gravity  of  1. 100,  it  is  buoyed  up  to  the 
mark  100,  just  above  the  bulb.  The  intermediate  space  is  divided  i^o 
100  equal  parts,  and  consequently  will  indicate  intermediate  degrees  of 
sp.  gr.  This  is  the  most  useful  form  of  the  instrument,  though  not 
that  in  common  use.  The  specific  gravity  of  the  wort  for  ale  is 
usually  about  1.090  to  1.100  and  for  table  beer  from  1.020  to  1-030. 

t The  distillers  prepare  a liquor,  called  wash , for  the  express  purpose 
of  producing  from  it  ardent  spirits;  instead  of  brewing  this  from  pure 
malt,  they  chiefly  employ  raw  grain,  mixed  with  a small  quantity  only 
of  malted  grain ; the  water  employed  in  the  mash-tun  is  of  a lower 


Fig.  198. 


50 


100 


488 


Product t of  Distillation . 


chap  tx-  2246.  Wine  is  principally  procured  from  the  juice  of  the  grape, 
Wine.  and  some  other  saccharine  and  mucilaginous  juices  of  fruits.  This 
sweet  juice  is  termed  must.  The  principal  substances  held  in  solu- 
tion in  grape  juice  are  sugar,  gum,  gluten,  and  tartrate  of  potassa. 
It  easily  ferments  spontaneously  at  temperatures  between  60°  and 
80°,  and  the  phenomena  it  gives  rise  to  closely  resemble  those  of 
the  wort  with  yeast.  After  the  operation,  its  sp.  gr.  is  much 
diminished,  its  flavour  changed,  and  it  has  acquired  intoxicating 
powers. 

Vinous  2247.  As  the  fermentation  of  must  takes  place  without  adding  any 
fermenta-  ferment,  it  is  obvious  that  the  requisite  substance  is  present  in  the  juice, 
tion.  This  was  separated  by  Fabroni  and  found  to  be  analogous  to  the  gluten 
of  plants;  and  gluten  being  substituted  for  it,  the  fermentation  suc- 
ceeded. He  has  shown  that  the  saccharine  part  of  must  resides  in 
the  cells  of  grapes,  while  the  glutinous  matter,  or  ferment,  is  lodged 
on  the  membranes  that  separate  the  cells.  It  is  only  after  the  juice 
is  squeezed  out  that  these  two  substances  are  mixed.  All  other 
juices  that  undergo  spontaneous  fermentation  have  been  shown  by 
Thenard  and  Seguin  to  contain  a similar  substance. 

Air  necea-  2248.  Gay  Lussac  has  shown  that  the  juice  of  fruits  will  not  fer- 
sary-  merit,  if  completely  excluded  from  the  air.  But  if  a little  oxygen 
gas  be  let  up  to  it,  this  gas  is  absorbed  and  fermentation  goes  on,  the 
carbonic  acid  evolved  being  100  times  as  great  as  that  of  the  oxygen 
absorbed.* 

2249.  It  seems  probable  that  the  tartaric  acid  is  partly  decomposed 
and  a portion  of  malic  acid  formed  during  the  process,  which  is 
analogous  to  combustion,  being  attended  by  the  evolution  of  caloric 
and  the  formation  of  carbonic  acid. 


Exp. 


2250.  If  a mixture  of  1 part  sugar, 
4 or  5 of  water,  and  u little  yeast,  be 
placed  in  a due  temperature,  it  also 
soon  begins  to  ferment,  and  gives  rise 
to  the  same  products  as  wort  or  grape- 
juice  ; and  the  results  may  easily  be 
examined  by  suffering  the  process  to 
go  on  in  the  apparatus  fig.  199,  con- 
sisting of  a mat  rice  containing  the 
fermenting  mixture,  with  a bent  tube 
issuing  from  it,  and  passing  into  an 
inverted  jar  standing  in  water. 


Fie.  199. 


Products  of  2251.  When  any  of  the  above-mentioned  fermented  liquors  are 
distillation,  distilled,  they  afford  a spirituous  liquor ; that  from  wine  is  termed 
brandy;  from  the  fermented  juice  of  the  sugar-cane  we  obtain 
rum  ; and  from  wash,  malt  spirit ; and  these  spirituous  liquors,  by 
re-distillation,  furnish  spirit  of  wine,  ardent  spirit,  or  alcohol. t 
Odourof  2252.  The  peculiar  odour  of  wine  is  owing  to  the  presence  of  a 
wines  small  quantity  of  a substance  analogous  in  properties  to  a volatile 


temperature  than  that  requisite  iu  brewing,  and  the  mashing  longer  continued ; by 
which  it  would  appear  lhat*a  part  of  the  starch  of  the  barley  is  rendered  into  a kind 
of  saccharine  matter.  The  wort  is  afterwards  fermented  with  yeast. 

* Ann.  de  Chim.  xvi.  245. 

t For  the  proportions  of  alcohol  furnished  by  different  fermented  liquors  see  p.  445. 
The  experiments  of  Brunde  {Phil.  Trans.  1811 — 13)  show  that  it  is  a real  educt.  See 
also  Henderson’s  Table  in  Brewster’s  Jour.  i.  166. 


489 


Acetification. 

oil.  It  amounts,  at  an  average,  to  about  4-77 Part  °f  wine.  Sect,  vi. 
It  may  be  obtained  by  distilling  the  lees  of  wine.  It  has  been  called  jEnanthic 
c znanthic  ether.  ^ ether. 

2253.  Acetous  fermentation.  When  any  of  the  vinous  liquors  are  Amenta 
exposed  to  the  free  .access  of  atmospheric  air  at  a temperature  of  ti0IK 
80°  or  85°  they  undergo  a second  fermentation,  terminating  in  the 
production  of  a sour  liquid,  called  vinegar.  Vinegar  is  usually  ob-  vinegar, 
tained  from  malt  liquor  or  cider,  while  wine  is  employed  as  its 
source  in  those  countries  where  the  grape  is  abundantly  cultivated. 

2254.  The  colour  of  vinegar  varies  according  to  the  materials  Properties, 
from  which  it  has  been  obtained;  that  manufactured  in  England  is 
generally  artificially  coloured  with  burnt  sugar  : its  taste  and  smell 

are  agreeably  acid.  Its  specific  gravity  is  liable  to  much  variation  ; 
it  seldom  exceeds  1.0250.  When  exposed  to  the  air  it  becomes  mouldy 
and  putrid,  chiefly  in  consequence  of  the  mucilage  which  it  con- 
tains, and  from  which  it  may  be  in  some  measure  purified  by  careful 
distillation. 

2255.  Neither  pure  alcohol,  nor  alcohol  diluted  with  water,  is  sus-  ^ 
ceptible  of  this  change.  The  weaker  the  wine  or  the  beer  the  more  undergo  the 
readily  it  is  converted  into  vinegar,  yet  strong  wines  yield  a better  change, 
vinegar,  so  that  alcohol  contributes  to  the  formation  of  the  acetic  acid. 

Wine  entirely  deprived  of  glutinous  matter  does  not  undergo  the 
acetous  fermentation,  until  some  mucilaginous  matter  is  restored 
to  it. 

2256.  Wine  which  is  completely  deprived  of  all  access  to  atmos*  >s 

pheric  air  never  becomes  sour.  In  order  to  understand  what  takes  formation 
place  during  the  conversion  of  alcohol  into  acetic  acid,  we  have  on^y  ”^cetic 
to  attend  to  the  constitution  of  these  two  bodies.  Alcohol  is  C4H50  aci 
-j-HO  while  acetic  acid  is  C4H303-j-H0.  In  the  first  place  2 atoms 

of  oxygen  are  absorbed  from  the  atmosphere  for  every  integrant 
part  of  alcohol  present.  These  combine  with  two  atoms  of  hydro- 
gen and  form  water,  leaving  the  alcohol  in  the  state  of  C4H30-|-H0, 
this  is  aldehyde.  The  aldehyde  has  a strong  affinity  for  oxygen  and 
absorbs  2 atoms  of  it  from  the  atmosphere,  and  is  converted  into 
C4H303-|-H0  or  acetic  acid.  Thus  during  the  conversion  of  alcohol 
into  acetic  acid,  every  atom  of  alcohol  absorbs  4 atoms  of  oxygen 
from  the  atmosphere  Here  unless  the  air  be  renewed  the  process 
ceases  to  go  on.  Even  when  the  process  is  properly  conducted 
about  Y^th  of  the  whole  acetic  acid  formed  is  lost.  But  when  the 
air  is  not  supplied  to  enable  the  aldehyde  to  absorb  oxygen  as 
fast  as  it  is  formed,  a great  deal  is  volatilized,  and  the  consequent  loss 
of  acetic  acid  may  be  very  great.! 

2257.  When  the  acetous  fermentation  is  over  the  whole  of  the  Ma]ic  acjd 
malic  acid  of  the  wine  has  disappeared  as  well  as  the  alcohol.  We  and  alcohol 
must  conclude  that  they  have  been  both  converted  into  acetic  acid.  dlsaPPears- 
Part  of  the  glutinous  matter  undergoes  the  same  change,  part  is  de- 
posited in  the  state  of  flakes,  and  part  remains  in  solution,  disposing 

the  vinegar  to  decomposition. 


* Ann.  de  Chim.  et  de  Phys.  lxiii.  113. 

t This  shows  the  necessity  on  the  part  of  manufacturers  of  perpetually  renewing  the 
air  of  their  chambers. 


62 


490 


Chap.  X. 

Sugar  es- 
sential. 

Panary 

fermenta- 

tion. 


Putrefac- 

tion. 


Offensive 
products . 


Proximate 

principles. 


Nitrogen. 


Ammonia. 


Organic  Chemistry — Animal  Substances. 

2258.  Sugar  appears  to  be  the  essential  constituent  in  liquors  to 
be  converted  into  vinegar  and  the  quantity  of  vinegar  formed  is  pro- 
portional to  the  sugar.  ^ T.  1032. 

2259.  Panary  fermentation.  The  change  which  dough  undergoes, 
attended  with  the  disengagement  of  carbonic  acid  gas,  has  been 
called  the  panary  fermentation.  The  adhesive  gluten  of  the  flour 
enables  it  to  be  distended  by  the  carbonic  acid  gas,  and  the  mass 
rises.  The  mean  heat  of  a baker’s  oven  is  448°,  this  stops  the 
fermentation,  and  the  detained  gas  is  expanded,  giving  to  the  loaf 
its  vesicular  structure.  Carbonate  of  ammonia  is  sometimes  em- 
ployed to  render  the  bread  porous. 

2260.  Putrefaction.  Vegetable  substances  are  decomposed  spon- 
taneously if  moist,  provided  the  air  has  access  to  them  and  the  tem- 
perature be  not  much  under  45°,  nor  so  high  as  to  drive  off  the 
moisture.  Plants  do  not  putrefy  in  vacuo,  or  at  least  very  slowly. 
If  placed  in  bottles,  well  closed,  and  exposed  to  the  temperature  of 
boiling  water  a partial  vacuum  is  formed  within  and  they  may  be 
kept  fresh  for  a considerable  length  of  time.t 

2261.  When  vegetables  contain  nitrogen  the  gases  given  off  du- 
ring putrefaction  are  peculiarly  offensive  ; this  is  the  case  with  the 
cruciform  plants,  and  wdien  sulphur  and  phosphorus,  it  is  much 
more  so.  When  these  substances  putrefy  on  the  surface  of  the 
ground,  they  leave  humus  or  vegetable  soil,  which  consists  chiefly  of 
the  extractive  matter  called  by  Berzelius  apotheme. 


CHAPTER  X. 

ANIMAL  SUBSTANCES. 

Section  I.  Ultimate  Principles  of  Animal  Matter,  and  Products 
of  its  Destructive  Distillation. 

2262.  The  proximate  principles  of  the  animal  creation  consist,  like 
those  of  vegetables,  of  a few  elementary  substances,  which  by  com- 
bination in  various  proportions,  give  rise  to  their  numerous  varieties. 
Carbon,  hydrogen,  oxygen,  and  nitrogen,  are  the  principal  ultimate 
elements  of  animal  matter ; and  phosphorus  and  sulphur  are  also 
often  contained  in  it.  The  presence  of  nitrogen  constitutes  the  most 
striking  peculiarity  of  animal,  compared  with  vegetable  bodies  ; but 
as  some  vegetables  contain  nitrogen,  so  there  are  also  certain  animal 
principles,  into  the  composition  of  which  it  does  not  enter. 

2263.  The  presence  of  nitrogen  stamps  a peculiarity  upon  the 
products  obtained  by  the  destructive  distillation  of  animal  matter,  and 
which  are  characterized  by  the  presence  of  ammonia,  formed  by  the 
union  of  the  hydrogen  with  the  nitrogen.  It  is  sometimes  so  abun- 


* Seven  water,  one  sugar,  and  some  yeast  ferment  in  a proper  temperature  and  form 
an  excellent  vinegar.  Ann.  de  Ckim.  lxii.  248.  For  a full  account  of  the  processes  see 
Ure’s  Diet.  A.  and  M.  1. 

t On  this  is  founded  the  method  of  preserving  vegetables,  fruits,  &c.  See  Ure’s 
Diet.  A.  and  M.  1045. 


Putrefaction. 

antly  generated  as  to  be  the  leading  product ; thus,  when  horn, 
oofs,  or  bones,  are  distilled  per  se,  a quantity  of  solid  carbonate  of 
mmonia,  and  of  the  same  substance  combined  with  ernpyreumatic 
il,  and  dissolved  in  water,  are  obtained  ; hence  the  pharmaceutical 
reparations  called  spirit  and  salt  of  hartshorn , and  Dippel’s  animal 
il.  Occasionally  the  acetic,  benzoic,  and  some  other  acids  are 
>rmed  by  the  operation  of  beat  on  animal  bodies,  and  these  are 
>und  united  to  the  ammonia;  cyanogen  and  hydrocyanic  acid  also 
equently  occur. 

2264.  If  the  gas  evolved  during  the  decomposition  of  animal  bo- 
ies  be  examined,  it  is  generally  inflammable,  and  consists  of  carbu- 
;tted  hydrogen,  often  with  a little  sulphuretted  and  phosphuretted 
ydrogen  ; carbonic  oxide,  carbonic  acid,  and  nitrogen  are  also  some- 
mes  detected  in  it. 

The  coal  remaining  in  the  retort  is  commonly  very  difficult  of  iti- 
neration, a circumstance  depending  upon  the  common  salt  and 
hosphate  of  lime,  which  it  usually  contains,  forming  a glaze  upon 
s surface  which  defends  the  carbon  from  the  action  of  the  air. 
.nimal  charcoal  is  also  found  to  be  more  effectual  in  destroying  co- 
•ur  and  smell,  than  that  obtained  from  vegetables. 

2265.  By  the  term  putrefaction  we  mean  the  changes  which  dead 
aimal  matter  undergoes,  and  by  which  it  is  slowly  resolved  into  new 
roducts.  These  changes  require  a due  temperature,  and  the  pre- 
mce  of  moisture  ; for  below  the  freezing  point  of  water,  or  when 
srfectly  dry,  it  undergoes  no  alteration. 

During  putrefaction  the  parts  become  soft  and  flabby,  they  change 
i colour,  exhale  a nauseous  and  disgusting  odour,  diminish  consi- 
srably  in  weight,  and  afford  several  new  products,  some  of  which 
scape  in  a gaseous  form,  others  run  off  in  a liquid  state,  and  others 
re  contained  in  the  fatty,  or  earthy  residuum. 

The  presence  of  air,  though  not  necessary  to  putrefaction,  materi- 
ily  accelerates  it,  and  those  gases  which  contain  no  oxygen,  are 
3ry  efficient  in  checking  or  altogether  preventing  the  process.  Car- 
Dnic  acid  also  remarkably  retards  putrefaction  ; and  if  boiled  meat 
3 carefully  confined  in  vessels  containing  that  gas,  it  remains  for  a 
ery  long  time  unchanged,  as  seen  in  Appert’s  method  of  preserving 
teal.* 


* This  method  is  now  successfully  practised  in  England,  upon  the  great  commercial 
ale,  for  keeping  beef,  salmon,  soups,  &c.  perfectly  fresh  and  sweet  for  exportation, 
he  process  is  as  follows  ; Let  the  substance  to  be  preserved  be  first  parboiled,  or  ra- 
er,  somewhat  more,  the  bones  of  the  meal  being  previously  removed.  Put  the  meat 
to  a tin  cylinder,  fill  up  the  vessel  with  seasoned  rich  soup,  and  then  solder  on  the 
1,  pierced  with  a small  hole.  When  this  has  been  done,  let  the  tin  vessel  thus  pre- 
ired  be  placed  in  brine  and  heated  to  the  boiling  point,  to  complete  the  cooking  of  the 
eat.  The  hole  of  the  lid  is  now  to  be  closed  by  soldering,  whilst  the  air  is  rarefied, 
he  vessel  is  then  allowed  to  cool,  and  from  the  diminution  of  volume,  in  consequence 
‘the  reduction  of  temperature,  both  ends  of  the  cylinder  are  pressed  inwards  and  be- 
>me  concave.  The  tin  cases,  thus  hermetically  sealed,  are  exposed  in  a test-chamber, 
r at  least  a month,  to  a temperature  above  what  they  are  ever  likely  to  encounter  ; 
om  90°  to  110°  F If  the  process  has  failed,  putrefaction  takes  place,  and  gas  is 
solved,  which  will  cause  the  ends  of  the  case  to  bulge,  so  as  to  render  them  convex, 
stead  of  concave.  But  the  contents  of  those  cases  which  stand  the  test  will  infalli- 
y keep  perfectly  sweet  and  good  in  any  climate,  and  for  any  number  of  years.  If 
ere  be  any  taint  about  the  meat  when  put  up,  it  inevitably  ferments,  and  is  de- 
cted  in  the  proving  process. 

For  a variety  of  details  and  methods  of  preserving  animal  and  vegetable  substances 
se  Ure’s  Did.  Arts  and  Manuf.  1046. 


491 


Sect.  I. 


Carburet- 
ted  hydro- 
gen. 


Putrefac- 

tion. 


Antisep- 

tics. 


Method  of  pre- 
serving meats, 
&c. 


492 


Chap.  X. 


Effect  of 
the  effluvia. 


Fumiga- 

tion. 


Adipocere. 


Fibrin. 

Properties. 

Action  of 
acids. 


Albumen. 


Organic  Chemistry — Animal  Substances. 

There  are  several  substances  which,  by  forming  new  combinations 
with  animal  matter,  retard  or  prevent  putrefaction,  such  as  chlorine 
and  many  of  the  saline  and  metallic  compounds ; sugar,  alcohol,  vo- 
latile oils,  acetic  acid,  and  many  other  vegetable  substances  also 
stand  in  the  list  of  anti-putrefactives,  though  their  mode  of  operating  is 
by  no  means  understood. 

2266.  The  effluvia  which  arise  from  putrescent  substances,  and 
more  especially  those  generated  in  certain  putrid  disorders,  have  a 
tendency  to  create  peculiar  diseases,  or  to  give  the  living  body  a ten- 
dency to  produce  poisons  analogous  to  themselves.  An  atmosphere 
thus  tainted  by  infectious  matter,  may  be  rendered  harmless  by  fumi- 
gation with  the  volatile  acids,  more  especially  the  nitrous  and  the 
hydrochloric  ; chlorine  is  also  very  effectual:  the  vapour  of  vinegar, 
though  sometimes  useful  in  covering  a bad  smell,  is  not  to  be  relied 
on.  It  appears  evident  that  the  acid  and  chlorine  act  chemically  upon 
the  pernicious  matter,  and  resolve  it  into  innocuous  principles. 

2267.  When  muscular  flesh  is  immersed  in  a stream  of  running 
water,  it  is  partially  converted  into  a substance  having  many  of  the 
properties  of  fat  combined  with  a portion  of  ammonia.  The  same 
changes  have  been  observed  where  large  masses  of  putrefying  ani- 
mal matter  have  been  heaped  together,  or  where  water  has  had  occa- 
sional access  to  it.  Nitrate  of  ammonia  is  also  sometimes  formed 
under  the  same  circumstances. 


Section  II.  Fibrin,  tyc. 

2268.  Fibrin  is  the  principal  part  of  muscular  fibre,  and  is  found 
also  in  the  blood  of  animals.  It  is  solid,  tasteless,  inodorous ; has  a 
whitish  appearance  : some  elasticity,  and  is  rendered  hard  and  brittle 
by  drying.  Soluble  in  strong  acetic  acid,  swelling  at  first,  and 
forming  a concentrated  jelly. 

2269.  It  is  decomposed  by  strong  and  by  diluted  nitric  acid,  pure  ni- 
trogen being  evolved  from  it  when  the  acid  is  diluted  ; a yellow  pow- 
der, called  yellow  acid , is  formed  during  the  reaction  of  the  nitric 
acid.  Berzelius  has  affirmed  that  it  is  a compound  of  nitric  acid  and 
fibrin  after  it  has  been  affected  by  the  acid.  With  sulphuric  acid, 
a solution  is  procured,  containing  a peculiar  white  matter  called  leu- 
cine ; the  sulphuric  acid  is  separated  from  it  by  chalk,  the  solution  of 
the  leucine  being  then  filtered  and  evaporated.  Diluted  hydrochlo- 
ric acid  has  little  action  on  fibrin,  and  by  the  strong  acid  it  is  de- 
composed. Fibrine  is  also  dissolved  by  concentrated  solutions  of 
potassa,  soda,  and  ammonia,  being  at  the  same  time  decomposed. 
It  is  insoluble  in  water  ; alcohol  converts  it  into  a fatty  matter. 

2270.  It  is  procured  from  muscular  fibre  by  macerating  it  in  water, 
or  by  stirring  newly  drawn  blood  with  a stick,  when  it  collects  in  con- 
siderable quantity  upon  it. 

The  analysis  of  fibrin  affords  carbon  53,  hydrogen  7,  nitrogen  19, 
oxygen  19. 

2271.  Albumen , 50  carb.,  7 hyd.,  15  nit.,  26  oxy.,  is  found  abun- 
dantly in  the  solid  form,  and  in  solution  in  water,  constituting  in  the 
latter  case  liquid  albumen. 


Bone,  Muscle , fyc. 


493 


2272.  Solid  albumen  is  found  in  the  cellular  membrane,  and  in  Sect,  in. 
a great  number  of  other  animal  solids.  Liquid  albumen  forms  the  Solid  Albu- 
white  of  the  egg,  and  almost  the  whole  of  the  serum  of  the  blood.  men 

It  is  a thick  fluid,  distinctly  alkaline  from  the  presence  of  soda,  com- 
bines with  cold  water,  and  is  coagulated  at  160°  by  heat  ; it  is  also 
coagulated  by  alcohol,  by  sulphuric,  nitric,  hydrochloric,  metaphos-  Properties, 
phoric,  and  many  other  acids ; by  ferrocyanate  of  potassa  after  the 
addition  of  acetic  acid  ; by  bichloride  of  mercury,  hydrochlorates  of 
tin  and  iron,mcetate  of  lead,  and  by  the  infusion  of  galls.  Phospho- 
ric and  pyrophosphoric  acids  do  not  precipitate  it.  The  coagulated 
albumen  generally  carries  along  with  it  a portion  of  the  precipitating 
agent. 

2273.  With  bichloride  of  mercury,  a precipitate  of  chloride  of  mer- 
cury and  albumen  is  formed  ; or  of  the  oxide  of  mercury,  according 

to  more  recent  investigation.  Bichloride  of  mercury  detects  albumen  Coagulated 
in  2000  parts  of  water. ^ An  excess  of  albumen  dissolves  those  pre-  g^^cif0 
cipitates  which  are  compounds  of  albumen  and  an  oxide.  It  is  also 
instantly  coagulated  by  Voltaic  electricity  ; and  if  two  platinum  wires 
connected  with  a small  battery  be  immersed  into  diluted  albumen,  a 
very  rapid  coagulation  will  take  place  at  the  negative  pole,  and 
scarcely  any  effect  at  the  positive  pole. 

2274.  Albumen  coagulated  by  heat,  or  by  drying  successive  layers 
in  the  open  air,  resembles  nbrine  much,  and  can  scarcely  be  distin- 
guished from  it  by  the  action  of  tests.  Berzelius  states  that  it  has  no 
action  on  binoxide  of  nitrogen,  but  that  fibrine  produces  a disengage- 
ment of  oxygen. 

2275.  Gelatine , 47  carb.,  7 hyd.,  16  nit.,  27  oxy.,  is  not  found,  Gelatine, 
like  the  preceding  substances,  in  any  animal  fluids.  It  is  obtained  prin- 
cipally from  skin,  bones,  membranes,  ligaments,  and  tendons.  Isin- 
glass is  a purer  variety,  which  is  prepared  from  the  sounds  of  the 
sturgeon  and  other  fish.  It  is  solid,  soluble  in  water,  hot  or  cold  ; not 
coagulated  by  heat  or  acids  ; forms  a solution  which  gelatinizes  when 

cold,  even  when  100  parts  of  water  are  used  with  only  1 of  gelatine. 

Tannin  precipitates  it  copiously;  the  compound  is  called  tanno-gela- 
tine,  and  is  of  the  same  nature  with  leather,  which  is  usually  pre- 
pared by  the  action  of  tannin  (derived  from  oak-bark)  with  the  skins 
of  animals.  Glue  consists  of  impure  gelatine.  Gelatine  is  insoluble  in 
water  ; converted  into  a peculiar  saccharine  matter  by  sulphuric  acid  ; 
not  precipitated  by  bichloride  of  mercury  or  subacetate  of  lead. 

2276.  Osmazome  is  found  associated  with  muscular  fibre  and  Osmazome. 
other  animal  matters;  it  is  particularly  distinguished  by  its  solubi- 
lity in  water  and  alcohol  at  any  temperature,  and  by  not  forming  a 
gelatinous  solid  when  its  solution  is  evaporated.  Osmazome  is  re- 
garded as  the  matter  which  gives  to  broth  its  peculiar  flavour. 


Section  III.  Bone,  Muscle,  fyc. 

2277.  Bones  contain  about  33  per  cent,  of  animal  matter,  and  67  Bones 
of  earthy  substances.  The  animal  matter  is  composed  principally  of  c 
gelatine  and  marrow  or  fatty  matter.  The  following  are  the  compo- 


* Bostock,  in  Nicholson’s  Jour xiv. 


494 


Chap  X. 


Analysis 

bones. 


Effect  of 
heat. 


Horns,  &c. 

Hair. 

Brain. 


Blood. 


Organic  Chemistry — Jlnimal  Substances. 

nent  parts  of  the  earthy  matter  in  100  parts  of  bones,  omitting 
fractions  : — 

Phosphate  of  lime,  about  . . . .51  parts. 

Carbonate  of  lime,  . . . . . 11  “ 

Fluoride  of  calcium,  . . . 2 “ 

Phosphate  of  magnesia,  . . 1 “ 

Soda,  chloride  of  sodium,  and  water  in  smaller  proportion. 

Silica  and  alumina,  with 

Oxides  of  iron  and  manganese,  have  also  been  detected. 

2278.  Exposed  to  heat  in  the  open  air,  the  animal  matter  is  con- 
sumed, and  the  earthy  substances  alone  left.  Exposed  to  heat  with- 
out access  of  air,  ammonia,  inflammable  gases,  oily  matter,  water, 
and  other  substances,  are  evolved,  much  of  the  carbon  of  the  decom- 
posed animal  matter  remaining  with  the  earthy  substances  of  the 
bone.  In  this  condition  it  is  termed  ivory  black , which  is  much  em- 
ployed as  a decolourizing  agent,  charcoal  from  animal  substances 
(2210)  being  very  powerful  in  this  respect.  If  the  charcoal  be  re- 
quired perfectly  free  from  earthy  matter,  hydrochloric  acid  may  be 
employed  to  dissolve  it ; and  when  it  has  been  removed  by  solution, 
the  remaining  charcoal  should  be  well  washed,  and  heated  to  red- 
ness, before  it  is  used  to  destroy  animal  or  vegetable  colouring 
matter. 

2279.  If  bones  be  kept  for  some  time  in  diluted  hydrochloric  acid, 
all  earthy  matter  is  removed,  and  the  animal  matter  which  remains 
retains  the  original  form  of  the  bone. 

2280.  Teeth  are  composed  of  the  same  materials  as  bones,  but 
contain  less  animal  matter. 

2281.  Horns , hoofs , nails , tendons , the  cuticle , and  the  true  skin , 
are  composed  principally  of  gelatine  ; horns  contain  also  coagulated 
albumen,  and  a portion  of  earthy  matter. 

2282.  The  muscles  are  composed  principally  of  fibrine,  with  albu- 
men, gelatine,  osmazome,  fatty,  and  saline  matter. 

2253.  Hair , wool , and  feathers , are  considered  to  contain  a pecu- 
liar animal  matter.  Silica,  sulphur,  iron,  manganese,  and  other 
substances,  more  particularly  salts  of  lime,  have  also  been  detected 
in  them. 

2254.  In  brain  and  the  matter  of  the  nerves,  80  per  cent,  of  water 
are  found.  Albumen,  fatty  matter,  and  osmazome,  constitute  the 
other  principal  ingredients.  A variable  proportion  of  phosphorus 
has  also  been  detected,  along  with  minute  quantities  of  salts  and 
sulphur. 


Section  IV.  Blood , Respiration  i Animal  Heat. 

2285.  The  blood  is  a fluid  slightly  saline,  unctuous,  and  has  a pe- 
culiar odour.  Sp.  gr.  105,  and  temperature  above  97°  when  newly 
drawn,  or  while  circulating  in  the  bloodvessels ; it  appears  to  be  ho- 
mogeneous, but  by  the  microscope  it  is  found  to  consist  of  a fluid 
almost  without  colour,  in  which  numerous  red  particles  are  sus- 
pended. 

2286.  When  removed  from  the  bloodvessels,  a halitus  or  vapour 
arises  from  the  surface,  composed  of  water  and  a little  animal  mat- 
ter, and  after  a few  minutes  the  whole  mass  gradually  assumes  a 


Blood. 


495 


solid  consistence.  Shortly  afterwards  a few  drops  of  yellowish  fluid  Sect.  iv. 
gather  on  the  top,  and,  finally,  the  blood  spontaneously  separates  into 
two  parts,  the  clot  or  crassamentum,  which  is  thick  and  solid,  and 
the  serum  or  fluid  portion.  From  2 to  3 parts  of  crassamentum  are 
usually  procured,  with  1 of  serum. 

2287.  The  conversion  of  the  fluid  mass  into  the  solid  form  is  Coagula- 
called  the  coagulation  of  the  blood,  and  it  commences  within  two  or'JjjjJJJ** 
three  minutes  after  its  removal  from  the  bloodvessels  ; the  clot  or  bl0°  * 
coagulum,  however,  often  continues  to  contract  slightly  for  two  or 

three  days  ; it  then  assumes  the  form  of  a cup,  and  floats  amidst  the 
serum.  The  cause  of  the  coagulation  is  not  known  ; it  has  been 
attributed  to  a vital  action,  the  blood  being  considered  to  have  the 
property  of  vitality  as  well  as  the  living  solids.  It  indeed  contains 
organized  solids  floating  in  a transparent  medium. 

2288.  The  coagulation  is  accelerated  by  exposing  the  blood  to  a Accelera- 
temperature  of  120°,  or  drawing  it  from  a small  orifice  into  a shallow  led> 
vessel. 


2289.  It  coagulates  quickly  if  the  air  be  rapidly  exhausted  from 
the  vessel  in  which  it  is  received  ; and  it  has  been  observed  to  coa- 
gulate speedily  in  proportion  to  the  depression  of  the  vital  energies, 
as,  for  instance,  in  hoemorrhage.  Hence  the  blood  last  removed  ge- 
nerally coagulates  first.  Alum,  and  the  sulphates  of  zinc  and  copper, 
promote  this  change.  The  tint  of  coagulum  is  much  affected  by  the 
colour  of  the  vessel  in  which  the  blood  is  received. 

2290.  Saturated  solutions  of  hydrochlorate  of  soda,  hydrochlorate  Prevented, 
of  ammonia,  nitrate  of  potassa,  and  potassa,  death  arising  from  vio- 
lent mental  emotions,  or  preceded  by  severe  exercise,  prevent  the 
process  of  coagulation.  Low  temperatures  produce  a similar  effect, 

or  retard  it  much  ; thus,  blood  which  coagulates  in  five  minutes  at 
60°,  requires  fully  an  hour  at  40°. 

2291.  It  has  been  stated  that  the  blood  does  not  coagulate  in  cases 
of  death  induced  by  lightning,  but  this  has  lately  been  contradicted. 

In  animals  killed  by  a powerful  galvanic  battery  the  blood  has  been 
found  coagulated. 

2292.  Besides  a particular  exhalation  from  the  blood,  heat  is 
evolved  during  coagulation.  Carbonic  acid  gas  was  supposed  to  be 
disengaged;  but  it  is  not  now  considered  that  any  of  this  gas  is 
evolved. 

2293.  The  blood  according  to  M.  Le  Canu,  consists  of  the  follow-  Composi- 

ing  substances  in  1000  parts  : tion/ 


Water,  .......  785.590 

Fibrin,  .......  3.565 

Albumen,  - - - . . . 69.415 

Colouring  matter,  ......  119.626 

Crystalline  fatty  matter,  termed  Seroline,  (Cholesterine  ?)  - 4.300 

Oily  matter,  2.270 

Extractive  soluble  both  in  alcohol  and  water,  - - 1.920 

Albumen  combined  with  soda,  ....  2.010 

Chlorides  of  sodium  and  potassium,  with  phosphates,  sulphates, 

carbonates,  of  potassa  and  soda,  ....  7.304 

Carbonates  of  lime  and  magnesia ; phosphates  of  lime,  magne- 
sia, and  iron  ; peroxide  of  iron,  ....  1.414 

Loss, - - - 2.586* 


* According  to  Gmelin  and  Tiedeman  blood  does  not  contain  free  carbonic  acid. 

See  their  Researches  on  Blood  in  Rec.  of  Gen . Sci.  1.  56. 


496 


Chap.  X. 


Peculiar 

volatile 

matter. 


Effect  of 
bleedings. 


Crassa* 

mentum. 


Colouring 

matter. 


Action  of 
chlorine. 


Obtained. 


Organic  Chemistry — Animal  Substances. 

2294.  Small  portions  of  alumina,  silica,  and  manganese,  have 
been  found  in  the  blood,  and  even  a minute  trace  of  copper,  by 
Sarzeau  and  O’Shaughnessy. 

2295.  Baruel  maintains  that  the  blood  contains,  in  addition  to  the 
preceding  principles,  a volatile  matter  peculiar  in  each  species, 
which  is  disengaged  when  the  blood  is  mixed  with  strong  sulphu- 
ric acid. 

2296.  The  proportion  of  the  different  substances  in  blood  varies 
at  different  periods  of  life,  in  different  individuals,  and  in  disease. 
The  proportion  also  of  the  serum  to  the  clot  varies  much  from  the 
shape  of  the  vessel  in  which  the  fluid  is  received.  The  fatty  mat- 
ter has  been  regarded  as  Cholesterine. 

2297.  From  experiments  made  on  the  changes  produced  in  the 
composition  of  the  blood  by  repeated  bleedings,  it  appears  that  the 
albumen  and  salts  decrease  at  each  bleeding  ; the  diminution  is, 
however,  very  variable,  and  even  after  the  fourth  time  does  not 
amount  to  one  and  a half  per  cent.  In  the  globules  the  same  dimi- 
nution takes  place,  but  to  such  a degree  that  they  are  at  least  re- 
duced to  less  than  one-half  their  original  quantity. 

2298.  The  proportion  of  solid  matter  of  the  serum,  and  solid 
matter  of  the  clot,  is  variously  estimated,  but  Prevost  and  Dumas 
give  the  following  relative  quantities,  in  1000  parts  of  human 
blood 

Water, 784 

Solid  matter  of  crassamentum,  - - 129 

-serum,  87 

2299.  In  the  Crassamentum  the  principal  solids  are  the  fibrine  and 
colouring  matter  of  the  blood,  mixed  with  albumen  derived  from  the 
serum.  By  washing  in  a cloth  with  water,  all  the  colouring  matter 
may  be  removed,  the  fibrine  being  left.  The  fibrine  is  found  not 
only  in  the  red  globules,  but  also  in  solution  in  the  serum,  as  it  cir- 
culates in  the  living  system. 

2300.  Colouring  matter  of  the  blood.  Regarded  formerly  as  de- 
pending essentially  upon  iron  for  its  tint,  which  is  attributed  now  to 
a peculiar  animal  matter  resembling  albumen,  and  called  Hemato- 
sine.  It  differs  from  albumen  in  its  colour,  and  is  black  when  pure; 
it  has  a reddish  colour  when  reduced  to  powder.  It  is  more  easily 
coagulated  by  heat  than  albumen,  and  is  not  precipitated  by  the  ace- 
tate or  subacetate  of  lead.  It  contains  carbon,  oxygen,  hydrogen, 
and  nitrogen,  with  a minute  quantity  of  iron.  It  acts  with  other  agents 
in  the  same  manner  as  albumen. 

2301.  When  chlorine  is  transmitted  through  a solution  of  the 
colouring  matter,  a white  flocculent  matter  is  precipitated,  and  a 
transparent  fluid  is  obtained,  in  which  the  iron  may  be  detected  by 
all  the  usual  tests.  Iron  cannot  be  detected  by  the  usual  reagents, 
when  dissolved  in  a solution  containing  organic  matter. 

2302.  It  is  obtained  by  diluting  a solution  of  colouring  matter  in 
albumen  with  10  parts  of  water,  and  heating  the  liquid,  when  the 
colouring  matter  is  separated  by  coagulation  at  the  temperature  of 
149°,  while  albumen  remains  in  solution  till  heated  to  160°.  It  is 
also  precipitated  by  several  metallic  oxides.  A solution  of  the 
colouring  matter  in  excess  may  be  procured  by  stirring  the  clot  in 


Endosmose — Ex  osmose . 


497 


water,  having  drained  it  previously  on  bibulous  paper,  after  cutting  Sect.  IV. 
it  in  thin  slices.  The  solution  of  colouring  matter  in  albumen 
is  procured  by  stirring  newly  drawn  blood,  so  as  to  remove  the 
fibrme. 

2303.  Erithrogen  (from  bqvOqos,  ruber)  is  a term  applied  by  Bizio  Erithrogen. 
to  a peculiar  animal  principle  obtained  by  him  in  a diseased  gall- 
bladder, and  which  he  considered  as  the  base  of  the  colouring  mat- 
ter of  the  blood.  It  is  turned  red  by  nitrogen. 

2304.  The  serum  constitutes  the  fluid  portion  of  the  blood  ; it  is  gerum 
of  a pale  yellow  colour,  with  a slight  tinge  of  green,  and  sometimes 
presents  a milky  appearance.  Sp.  gr.  1.030.  It  contains  free  alka- 
li (soda.) 

2305.  It  is  coagulated  by  heat,  acids,  alcohol,  and  by  galvanism.  Effect  of 
On  cutting  and  pressing  the  coagulum  when  produced  by  heat,  a small  heat,  &c. 
quantity  of  colourless  limpid  fluid  exudes,  called  the  serosity , con- 
taining a considerable  portion  of  the  saline  matter  of  the  blood,  and 

also  a portion  of  animal  matter. 

2306.  According  to  Marcet,  1000  parts  of  the  serum  consist  of — Analysis 


Water,  -----  900. 

Albumen,  -----  86.8 

Hydrochlorate  of  potassa  and  soda,  - 6.6 

Muco-extractive  matter,  4. 

Carbonate  of  soda,  - - - - 1.65 

Sulphate  of  potassa,  - - - 0 35 

Earthy  phosphates,  - - - - 0.60* 


2307.  Respiration  consists  in  the  inspiration  and  expiration  of  air,  ReSpira„ 
during  which  the  air  received  into  the  lungs  meets  with  the  blood,  tion. 
when  it  changes  from  the  dark  purple  colour  of  venous  blood  to  the 
bright  and  brilliant  red  colour  which  it  presents  in  the  arteries.  No 
difficulty  is  now  entertained  with  respect  to  the  air  penetrating 
through  the  thin  membrane  of  the  cells  of  the  lungs,  as  numerous 
experiments,  particularly  those  of  Mitchellt  and  Faust,  have  shewn 

that  air  can  pass  through  membranous  matter,  and  affect  chemi- 
cally the  contents  within. 

2308.  The  experiments  on  the  diffusion  of  gases  illustrate  the  Exp. 
passage  of  air  through  apertures  impervious  to  water  ; while  the 
movements  that  take  place  in  different  fluids  separated  by  a mem- 
branous partition,  also  clearly  prove  the  facility  with  which  an  inter- 
change of  principles  can  ensue  with  great  force  where  it  was  not 
previously  suspected.  Dutrochet,  who  made  many  interesting  ex- 
periments on  this  subject,  found  that  a bladder  filled  with  a sirupy 
fluid  and  placed  in  water,  soon  absorbed  so  much  of  the  water  that 

it  burst,  a portion  of  the  viscid  fluid  also  escaping  through  the  pores.  Endosmose 
Endosmose  is  the  term  applied  to  this  peculiar  action  as  it  is  observ-  and  exos- 
ed  in  liquids,  and  exosmose  to  the  passage  of  a portion  of  fluid  from  & 
the  interior  to  the  other  portion  of  liquid  with  which  it  may  be  sur- 
rounded ; this  exosmic  movement  always  accompanies  the  endosmic 
action.  The  extensive  surface  on  which  the  fluid  is  spread  in  the 


* A valuable  paper  on  Blood  and  Chyle  by  Muller  will  be  found  in  Rec.  of  Gen . 
Sci.  i.  424. 

iAmer.  Jour.  Med.  Sci.  Philad. 

63 


498 

Chup.  X. 


Effect  of 
air,  &c. 


Arteriali- 

zation. 


Oxygen  re- 
moved, 


And  carbo- 
nic acid 
formed, 


Its  quanti- 
ty. 


Animal 

heat. 


Organic  Chemistry — Animal  Substances . 

cells  of  the  lungs,  must  be  peculiarly  favourable  for  the  absorption 
of  oxygen  from  the  air  by  the  blood,  and  the  evolution  of  carbonic 
acid. 

2309.  Blood  agitated  with  air  or  oxygen  becomes  of  a florid  red 
in  the  same  manner  as  in  the  lungs  ; but  with  nitrogen  and  with  car- 
bonic acid  the  colour  is  darkened.  The  quantity  of  air  affected  ap- 
pears to  correspond  with  the  amount  of  colouring  matter  in  the 
blood.  The  presence  of  saline  matter,  as  in  the  serum  of  the  blood, 
is  essential  to  the  change  of  colour  ; it  does  not  take  place  without 
it,  however  freely  the  air  or  oxygen  may  be  supplied,  as  Stevens 
proved.  The  experiments  of  Gregory  and  Irvine  have  shewn  that 
oxygen  is  necessary  to  induce  the  red  tint  in  the  globules  diffused 
through  serum,  or  any  similarly  diluted  solution  of  saline  matter,, 
though  the  change  may  be  produced  in  a strong  saline  solution 
without  any  oxygen.  Arterialization  is  the  term  applied  to  the 
changes  that  are  produced  in  the  fluid  derived  from  the  food,  as  it  is 
converted  into  blood. 

2310.  During  respiration,  the  quantity  of  oxygen  in  the  air  is 
diminished,  and  in  man  it  is  replaced  by  an  equal  bulk  of  carbonic 
acid  gas  ; in  other  animals,  the  quantity  of  this  gas  given  out  is 
occasionally  observed  to  be  greater,  and  sometimes  less  than  the 
oxygen  consumed.  Every  minute,  it  has  been  calculated  byAllen 
and  Pepys,  26  cub.  inches  of  carbonic  acid  are  produced,  an  estimate 
considered  rather  high  by  many  chemists  ; the  air  given  out  from 
the  lungs  contains,  according  to  other  estimates,  3.6  per  cent,  of 
carbonic  acid  ; according  to  them,  from  6 to  8 per  cent,  of  this  gas. 

2311.  The  quantity  of  carbonic  acid  according  to  Coathupe  is 
but  6.4  per  cent.  According  to  his  recent  experiments  460.800  cubic 
inches,  or  266.66  cubic  feet  of  air  pass  through  the  lungs  of  a healthy 
adult  in  24  hours,  of  which  10.666  cubic  feet  will  be  converted  into 
carbonic  acid  gas  =23S6.27  grs.  or  5.45  ounces  avoirdupois  of  car- 
bon. This  gives  99.6  grains  of  carbon  per  hour,  produced  by  the 
respiration  of  one  adult  or  124.328  pounds  annually.* 

2312.  The  experiments  of  Thomson,  Prout,  and  Fyfe,  shew  that 
the  quantity  of  carbonic  acid  evolved  at  different  temperatures  varies 
much  under  different  circumstances,  and  even  at  different  periods  of 
the  day. 

2313.  By  a forced  expiration,  about  200  cub.  inches  of  air  may, 
on  an  average,  be  expelled  from  the  lungs. 

2314.  The  nitrogen  of  the  air  is  little  affected,  apparently,  by  res- 
piration ; occasionally  its  quantity  appears  to  be  increased,  and 
sometimes  it  is  diminished,  the  effect  varying  with  the  seasons  and 
other  circumstances. 

2315.  Animal  heat.  The  discovery  of  carbonic  acid  in  the  air  dis- 
engaged from  the  lungs  during  respiration,  was  made  by  Black. 
He  considered  respiration  analogous  to  combustion,  and  that  the  car- 
bonic acid  is  formed  in  the  lungs.  Crawford,  adopting  his  views, 
believed  that  the  capacity  of  the  blood  for  caloric  is  increased  at  the 
moment  the  carbonic  acid  is  produced,  and  hence  the  reason  why 
no  burning  heat  is  perceived  in  the  lungs;  but  the  capacity  of  the 


* See  Coathupe’s  experiments  in  Lond.  and  Edin.  Philos.  Mag.  June,  1639. 


499 


Blood— Buffy  Coat . 

blood,  he  supposed,  is  diminished  as  it  passes  from  arterial  to  venous  Sect,  iv. 
blood  in  the  extreme  capillaries,  when  the  heat  that  had  originally  Theories? 
been  produced  (though  not  rendered  sensible  in  the  lungs)  is  evolved, 
diffusing  an  equal  degree  of  warmth  over  the  whole  body.  His  ex- 
periments, however,  as  to  the  relative  capacities  of  oxygen,  carbonic 
acid,  venous,  and  arterial  blood,  on  which  the  theory  rests,  have  not 
been  supported  by  other  chemists. 

2316.  Ellis  considered  that  carbon  is  separated  from  the  blood 
as  an  excreted  product,  and  then  acts  on  the  air  inspired. 

2317.  Hassenfratz  and  Le  Grange  proposed  another  view  of  the 
manner  in  which  the  carbonic  acid  is  produced,  and  it  is  most  gene- 
rally received  at  present.  They  considered  that  the  oxygen  of  the 
air  is  absorbed  by  the  blood,  and  a corresponding  quantity  of  car- 
bonic acid  evolved,  produced  during  the  course  of  the  circulation  by 
the  oxygen  which  had  been  previously  absorbed.  Carbonic  acid  gas 
has  been  detected  in  venous  blood,  being  evolved  when  it  is  trans- 
ferred directly  from  the  living  body  into  an  atmosphere  of  hydrogen 
gas. 

2318.  The  skin  affects  the  air  much  in  the  same  manner  as  the 
lungs,  carbonic  acid  being  produced  and  oxygen  consumed. 

2319.  In  some  animals,  respiration  is  carried  on  entirely  by  the 
skin,  and  a considerable  quantity  of  carbonic  acid  evolved. 

2320.  The  production  of  animal  heat  was  considered  by  Black  to  Black’s 
depend  upon  the  formation  of  carbonic  acid  by  the  oxygen  of  the  theory, 
air  combining  with  the  carbon  of  the  blood.  Numerous  experiments 
have  now  proved,  that  the  greater  the  heat  produced  in  the  body, 

the  greater  the  consumption  of  oxygen  in  the  lungs ; it  is  also  sup- 
posed that  this  operation  is  not  the  only  source  of  animal  heat,  but 
that  it  may  be  developed  in  part  by  other  operations  going  on  at  the 
same  time. 

2321.  By  disease,  blood  is  much  altered  in  its  properties.  In  Effect  of 
cases  of  cholera  it  is  very  much  affected;  its  colour  becomes  dark,  disease, 
sometimes  it  acquires  the  consistence  of  tar,  and  is  less  readily 
affected  by  the  oxygen  of  the  air.  It  loses  much  water,  and  most 

of  its  saline  matter,  the  proportion  of  albumen  and  colouring  mat- 
ter being  increased.  Its  density  is  greater,  and  it  does  not  co- 
agulate. 

2322.  Blood  occasionally  presents  a white  appearance,  owing  to 
the  presence  of  fatty  matter  in  considerable  quantity,  which  is  de- 
tected by  ether  dissolving  it,  and  giving  a solution,  from  which  it 
may  be  procured  by  evaporation. 

2323.  In  cases  of  inflammatory  action,  the  crassamentum  is  cov-  Buffy  coat, 
ered  with  a coat  of  pure  fibrin,  usually  called  the  buffy  coat.  This 

arises  from  the  blood  being  so  altered  in  its  qualities,  that  the  fibrin 
it  contains  in  solution  coagulates  more  slowly  than  the  rest  of  the 
blood,  and  part  of  it  is  deposited  above  the  red  clot.  The  red  glo- 
bules of  the  blood,  are  considered  heavier  than  pure  fibrin,  con- 
sisting of  a small  portion  of  colourless  fibrin  in  the  centre,  which 
is  surrounded  by  the  colouring  matter  of  the  blood.  When  the 
blood  is  removed  from  the  body,  and  the  colouring  matter  escapes 
from  the  globule,  the  fibrin  from  the  centre  adheres  firmly  to- 
gether. 


500 


Chap.  X. 

Effects  of 
disease  on 
blood. 


Saliva. 


Pancreatic 

juice, 


Gastric 

juice, 


Its  action 
on  food. 


Bile. 


Organic  Chemistry — Animal  Substances. 


2324.  The  blood  is  affected  to  a great  extent  in  a number  of  other 
diseases,  though  this  may  not  in  general  be  so  easily  recognised  as 
in  the  preceding  cases,  chemical  analysis  being  required  to  point 
out  the  change.  Occasionally,  however,  the  change  is  sufficiently 
evident,  as  in  jaundice,  when  the  blood  acquires  a greenish-yellow 
tint  in  consequence  of  the  absorption  of  bile.  The  black  vomit 
observed  in  yellow  fever  is  regarded  as  a compound  of  blood  and 
hydrochloric  acid.  Urea  is  frequently  observed  in  the  blood,  more 
especially  in  those  cases  when  the  secretion  of  urine  is  suppressed. 


Section  V.  Salivary , and  Gastric  Juices , Bile. 

2325.  The  Saliva  contains  a small  quantity  of  solids  in  solution, 
scarcely  amounting  to  1 per  cent.  The  solid  matter  is  composed  of 
a peculiar  animal  matter  and  saline  substances,  among  which  free 
soda  and  sulphocyanate  of  potassa  have  been  detected.  It  varies, 
however,  in  its  composition,  and  has  been  frequently  observed  acid, 
neutral,  and  alkaline. 

2326.  Pancreatic  juice.  Regarded  formerly  as  being  of  the  same 
nature  with  saliva,  though  now  considered  very  different,  containing 
a little  albumen,  curdy  matter,  osmazome,  a free  acid  (acetic?), 
but  no  sulphocyanic  acid  is  present. 

2327.  Gastric  juice.  This  fluid  is  secreted  in  its  proper  form  only 
from  the  stimulus  of  food,  when  hydrochloric  acid  may  be  distinctly 
traced  in  it,  to  which  the  great  solving  powers  which  it  possesses  are 
attributed;  acetic  acid  is  also  associated  with  it.  The  hydrochloric 
acid  is  probably  derived  from  common  salt,  and  to  the  soda  produced, 
as  the  hydrochloric  acid  is  removed,  the  alkaline  reaction  of  the 
blood  may  perhaps  be  attributed.  The  stomach  itself  is  supposed  to 
be  defended  from  the  action  of  the  corrosive  acid  by  assuming  a pe- 
culiar electric  condition.  In  cases  of  sudden  death,  the  stomach  is 
often  found  corroded  in  consequence  of  the  action  of  the  acid  on  its 
fibres.  Gastric  juice  acts  powerfully  in  coagulating  milk. 

232S.  The  gastric  juice  acting  on  the  food  produces  a pulpy  mass, 
termed  chyme,  from  which,  in  the  intestines,  a milky  fluid,  the 
chyle  is  absorbed  ; this  contains  the  nutritious  matter  derived  from 
the  food,  and  is  conveyed  to  the  heart,  and  thence  to  the  lungs, 
where  it  acts  with  the  air,  and  is  converted  into  arterial  blood. 

2329.  Bile  is  a greenish-yellow  coloured  fluid,  generally  rather 
viscid,  having  a sweetish  bitter  taste  and  nauseous  odour.  Heavier 
than  water,  alkaline  ; coagulated  by  acids. 

Thenard  regards  the  bile  of  the  ox  as  a compound  of  about  7 parts 
of  water  and  1 of  animal  and  saline  matter,  composed  of — 


Picromel.  Hydrochlorate  of  soda. 

Resin.  Hydrochlorate  of  potassa. 

Yellow  matter.  Sulphate  of  soda. 

Soda.  Phosphate  of  lime. 

Phosphate  of  soda.  Magnesia  and  oxide  of  iron. 

The  saline  matter  constitutes  a small  proportion  of  the  ingredients. 
Cholesterine,  an  odoriferous  animal  matter,  and  another  peculiar 
animal  matter,  osmazome,  gluten,  cholic  acid,  and  some  fatty  sub- 


See  experiments  of  Tiedemann  and  Gmelin  in  Ann.  de  Chim.  lix.  348. 


Caseous  Matter-— Chyle.  501 

stances,  have  also  been  found  in  bile;  In  human  bile,  similar  ingre-  Sect,  vi. 
dients  have  been  detected. 

2330.  Picromel.  Solid,  crystalline,  soluble  in  alcohol  and  water  ; picromel. 
taste  sweet.  Prepared  from  bile  by  precipitating  sulphuric  acid  and 

some  other  substances  by  acetate  of  le£d,  then  adding  subacetate  of 
lead,  the  oxide  falling  down  with  the  picromel  and  resin.  By  hydro- 
sulphuric  acid  acting  on  the  precipitate  suspended  in  water,  sulphuret 
of  lead  is  formed,  being  left  undissolved  along  with  the  resin  ; the 
picromel  remains  in  solution. 

2331.  Cholic  Acid  is  solid,  crystalline,  reddens  litmus,  and  has  a Cholic 
sweet  taste.  Biliary  Calculi  are  composed  principally  of  choleste-  acid* 
rine,  and  the  colouring  matter  of  the  bile.  Sometimes  they  contain 

no  cholesterine. 

2332.  Cholesterine  is  white,  crystalline,  with  a pearly  lustre.  Choleste- 
Melts  at  278°  ; does  not  form  a soap  with  potassa.  Insoluble  in  rine- 
water;  dissolved  abundantly  by  boiling  alcohol;  sparingly  soluble 

in  cold  alcohol.  By  the  action  of  nitric  acid,  cholesteric  acid  is 
produced. 


Section  VI.  Milk  and  Chyle. 

2333.  Milk  contains  the  following  substances,  of  which  the  first,  Milk, 
water,  constitutes  nearly  929  parts  in  1000 : — 

Water.  Hydrochlorate  of  potassa. 

Butter.  Acetate  of  potassa. 

Caseous  matter.  Phosphate  of  potassa. 

Sugar  of  milk.  Phosphate  of  lime. 

Lactic  acid.  Traces  of  iron. 

2334.  Cream  contains  rather  more  than  3 per  cent,  of  caseous  mat-  Cream, 
ter,  and  4 of  butter,  the  rest  being  whey. 

2335.  Whey  consists  principally  of  water,  with  small  portions  of  Whey, 
animal  matter,  and  a large  quantity  of  a peculiar  saccharine  matter, 
called  sugar  of  milk,  which  may  be  procured  by  evaporation. 

2336.  Butyrine  is  the  name  given  to  oily  matters  which  constitute  Butyrine. 
butter. 

2337.  Caseous  Matter  is  the  curdy  substance  obtained  from  milk  Caseous 
coagulated  by  rennet,  the  infusion  made  by  the  action  of  water  upon  matter‘ 
a portion  of  the  stomach  of  the  calf,  which  is  powerful  in  coagulating 
milk.  It  always  contains  in  this  condition  some  foreign  matter  asso- 
ciated with  it,  being  soluble  in  water  when  pure,  and  forming  a mu- 
cilaginous solution.  Sulphuric,  nitric,  hydrochloric,  and  other  acids  ; 
alcohol,  the  infusion  of  galls,  and  a variety  of  other  substances,  coa- 
gulate milk  by  combining  with  the  caseous  matter. 

2338.  Caseous  matter  is  maintained  by  some  chemists  to  contain 
two  distinct  principles,  caseic  acid , and  caseous  oxide  of  aposepi - 
dine.  Others  again  regard  it  as  approaching  very  nearly  to  coagu- 
lated albumen  in  its  leading  characters. 

2339.  Chyle  is  the  milky  looking  fluid  taken  up  from  the  chyme.  Chyle. 

It  approaches  in  its  characters  to  blood,  but  has  only  a slight  pink 

tint,  and  contains  less  solid  matter.  It  forms  a less  firm  crassamen- 
tum  during  coagulation,  and  from  its  serum  a flocculent  precipitate 
is  obtained  by  heat,  termed  byProut  incipient  albumen.  The  chyle 
of  two  dogs  analyzed  by  him  contained  from  89  to  94  of  water, 


502 


Organic  Chemistry — Animal  Substances. 


Chap,  x.  the  rest  being  fibrin,  incipient  albumen,  albumen  with  a slight  pink 
tint,  and  minute  quantities  of  sugar,  and  oily  and  saline  matters. 


Stearine. 


Section  VII.  Oleaginous  and  Fatty  Substances. 

2340.  These  resemble  jnuch  in  all  their  leading  characters  the 
fixed  oils  of  vegetables.  Stearine  is  found  in  most  of  them  asso- 
ciated with  variable  proportions  of  oleine.  Berard  prepared  a sub- 
stance very  similar  to  fat,  by  passing  through  a red-hot  tube  a mix- 
ture of  carbonic  acid,  carburetted  hydrogen,  and  hydrogen.  Dobe- 
reiner  succeeded  in  producing  an  analogous  compound  with  coal  gas 
and  watery  vapour. 

2341.  Stearine  is  obtained  with  facility  in  brilliant  crystals  when 
deposited  from  a hot  ethereal  solution.  It  is  very  soluble  in  hot 
ether,  sparingly  soluble  in  cold  ether.  It  is  also  soluble  in  boiling 
alcohol.  Melts  at  129°.  Prepared  by  boiling  mutton  suet  in  ether, 
after  melting  it  to  separate  any  membranous  matter,  and  removing 
the  adhering  solution  from  the  crystals  by  bibulous  paper  ; this  pro- 
cess is  repeated  with  the  crystals  several  times.  Similar  processes 
may  be  adopted  in  preparing  stearine  from  other  fatty  matters. 

2342.  When  boiled  with  a solution  of  potassa  or  soda,  it  is 
resolved  into  stearic  acid  and  glycerine.  The  stearic  acid  may  be 
separated  by  neutralizing  the  alkali  with  sulphuric  acid  (1690). 

2343.  Margarone  is  the  name  given  to  another  fatty  matter  very 
similar  to  stearine,  but  more  soluble  in  ether,  and  melting  at  117°. 
It  is  procured  by  allowing  the  matter  separated  from  the  stearine 
(1693)  to  evaporate  and  crystallize  spontaneously. 

2344.  Olein  is  obtained  by  pressing  lard  in  bibulous  paper,  to 
which  it  adheres.  It  is  similar  to  that  procured  from  vegetable  sub- 
stances.* 

2345.  Ambergris  is  considered  to  be  a concretion  produced  in  the 
Ambergris,  stomach  of  the  spermaceti  whale.  It  is  found  floating  on  the  sea 

coast  of  India  and  Africa.  It  consists  principally  of  a peculiar  fatty 
matter,  called  ambreine,  which  resembles  cholesterine.t 

2346.  j Dippers  Oil  is  the  name  given  to  a thin  limpid  oil,  the  pro- 
duct of  the  destructive  distillation  of  animal  substances. 

2347.  Fat , Hogs’-lard  and  Suet,  are  compounds  of  stearine  and 
oleine  in  various  proportions;  they  melt  at  various  temperatures  be- 
tween 59°  and  102°.  The  stearine  and  oleine  differ  often  in  the  fat 
obtained  from  different  animals. 

2348.  Hircine  is  procured  from  the  fat  of  the  goat  and  sheep. 

2349.  Spermaceti  is  prepared  from  the  fatty  matter  found  in  the 
head  of  the  spermaceti  whale.  Solid,  white,  crystalline,  insoluble  in 
water,  soluble  in  ether  and  alcohol.  Melts  at  a temperature  below 
212°.  It  is  usually  mixed  with  a little  fluid  oil,  and  is  termed 
eetine  when  purified  by  solution  in  boiling  alcohol  and  crystallization. 
Ethal  is  a solid  fatty  mutter  which  remains  after  the  separation  of 
margaric  and  oleic  acids  ; boiling  eetine  with  potassa  or  soda,  so  as 
to  produce  soap. 


Margarone. 


Olein. 


Dippel’s 

oil. 

Fat,  hogs- 
lard,  and 
suet. 


Hircine. 

Sperma- 

ceti. 


* Adipodre.  See  2267. 


t Cholesterine . See  Bile. 


Lactic  Acid. 


503 


2350.  Spermaceti  Oil  is  the  fluid  expressed  from  the  fatty  matter  Sect,  vm. 
from  which  the  spermaceti  is  obtained. 

2351.  Train  oil  is  procured  by  heating  blubber  to  212°.  Its  often-  Train  oil. 
sive  odour  arises  from  decomposed  animal  matters  which  are  mixed 

with  it. 


Section  VIII.  Mucus , Pus , fyc. 

2352.  Mucus.  The  existence  of  a distinct  principle  to  which  this  Mucus, 
name  has  been  applied  is  doubtful.  The  mucus  described  by  Bos- 

tock  is  soluble  in  hot  and  cold  water,  and  does  not  gelatinize.  Tan- 
nin and  bichloride  of  mercury  do  not  precipitate  it.  The  mucus  of 
the  nose  is  rendered  transparent  by  water,  but  not  dissolved.  It  is 
dissolved  by  nitric  acid,  dilute  sulphurie  acid,  and  potassa. 

2353.  Pus  varies  much  in  its  qualities,  according  to  the  nature  of  Pus. 
the  source  from  which  it  is  produced.  Healthy  pus  is  a bland,  thick 
fluid,  apparently  homogeneous,  but  composed  of  a thin  transparent 
fluid,  with  opaque  globules  floating  in  it.  Sp.  gr.  1.030.  Neutral, 
but  becomes  acid  by  the  action  of  the  air.  Soluble  in  sulphuric, 
nitric,  and  hydrochloric  acids,  and  in  alkalies.  Ammonia  produces 

a gelatinous  mass  with  it. 

2354.  The  following  are  the  principal  tests  which  have  been  pro 
posed  for  distinguishing  pus  from  mucus  : — 


Tests. 

Mixed  with  an  equal  weight  of 
water,  and  then  with  an  equal 
weight  of  a saturated  solution  of 
carbonate  of  potassa, 

Diffused  through  water. 

Dissolved  in  potassa,  and  water 
added, 

Dissolved  in  sulphuric  acid,  and 
water  added. 


Mucus. 

does  not  gelatinize. 


from  a catarrh,  it  floats, 
not  affected.  • 


remains  suspended  in 
the  water. 


Pus. 

produces  a jelly.  Tests  of 
mucus  and 
pus. 


precipitated. 

precipitated. 

precipitated. 


2355.  Fluid  of  Serous  Surfaces.  Composed  principally  of  water,  Fluid  0f  se- 
with  small  portions  of  albumen,  mucus,  and  saline  matter.  The  rous  sur- 
lymph  which  lubricates  the  cellular  membrane  is  considered  of  ana-  fac€s* 
logous  composition.  Small  portions  of  lactic  acid  are  also  found 

in  it. 

2356.  Lactic  acid  has  been  found  in  most  animal  fluids,  and  in  a Lactic  acid, 
number  of  vegetables  ; it  was  first  obtained  from  sour  milk,  from 

which  its  name  is  derived.  Its  concentrated  solution  is  sirupy,  very 
acid,  and  can  displace  acetic  acid  from  its  combinations.  It  is  pre- 
pared by  evaporating  solutions  containing  it  to  a sirupy  consistence, 
extracting  the  lactic  acid  by  alcohol.  By  combination  with  oxide  of 
zinc,  separating  it  afterwards  by  baryta,  and  ultimately  removing  the 
baryta  by  sulphuric  acid,  it  is  obtained  in  a pure  form.* 


* Formic  Acid  has  been  already  described  (1610). 


504 


Organic  Chemistry — Animal  Substances. 


Chap.  X. 
Urea. 


Uric  or  li- 
thic  acid 
prepared . 


Purpuric 

acid. 


Cyanuric 

acid. 


Urine. 


Analysis- 


Decom- 

posed. 


Section  IX.  Urea — Uric  Acid. 

2357.  Urea  has  been  already  described  (1742).  According  to 
Cass  and  Henry  it  does  not  exist  in  urine  uncombined,  but  united 
with  different  acids  in  different  beings ; in  man  combined  with  hip- 
puric  acid,  in  serpents  and  birds  with  lithic  acid,  or  at  least  with 
the  peculiar  acid,  which,  according  to  Liebig,  is  its  radical.* 

2358.  Uric  or  Lithic  Acid  may  be  prepared  from  calculi  of  uric 
acid,  or  from  the  uri9  acid  deposited  from  acidulated  urine,  by  dissol- 
ving it  in  a solution  of  potassa,  and  adding  an  acid  to  precipitate  it 
from  the  urate  of  potassa. t 

2359.  Purpuric  Acid  is  white  when  pure,  and  is  particularly  dis- 
tinguished by  the  brilliant  coloured  purple  compounds  which  it  forms 
with  several  of  the  salifiable  bases.  Formed  in  combination  with 
ammonia  by  the  action  of  nitric  and  uric  acids.  The  ammonia  may 
be  displaced  by  potassa,  and  the  purpuric  acid  precipitated  by  adding 
sulphuric  acid  to  combine  with  the  potassa.  The  erythric  acid  of 
Brugnatelli,  and  the  sediment  often  deposited  from  urine  in  fevers, 
and  called  at  one  time  rosacic  acid,  are  considered  by  Prout  to  be 
composed  of  purpurate  of  ammonia. 

2360.  Cyanuric  Acid,  called  also  Pyrouric  Acid , is  formed  when 
uric  acid  is  heated,  or  by  the  action  of  chlorine  on  different  compounds 
containing  cyanogen  and  water.  Urea  also  may  be  made  to  produce 
this  acid  (1761). 

2361.  A peculiar  colouring  matter,  not  containing  any  purpuric 
acid,  has  also  been  discovered  in  the  urine. 

2362.  Urine  is  a transparent  limpid  fluid,  of  an  amber  colour  ; sp. 
gT.  1.02244  when  recently  discharged  it  has  an  acid  reaction,  but  after 
a short  time  it  acquires  decided  alkaline  properties.  The  following 
are  the  component  parts  of  urine,  according  to  Berzelius,  in  1000 


parts  : — • 

Water,  - 933.00 

Urea, 30.10 

Uric  acid,  .....  1.00 

Free  lactic  acid,  and  lactate  of  ammonia  with  ani- 
mal matter,  - - - - - 17.14 

Mucus  of  the  bladder,  - 0.32 

Sulphate  of  potassa,  ....  3.71 

“ soda,  ....  3.16 

Phosphate  of  soda,  ....  2.94 

Phosphate  of  ammonia,  - - - 165 

llydrochlorate  of  soda  ....  4.45 

“ ammonia,  ....  1.50 

Earthy  matters  with  a trace  of  fluate  of  lime,  - 1.00 

Siliceous  earth,  ...  0.03 


Sulphur,  phosphorus,  and  albumen,  are  also  found,  but  in  very 
small  quantities.  In  children,  and  also  in  graminivorous  animals,  a 
considerable  amount  of  benzoic  acid  may  be  detected.  Its  sp.  gr. 
varies  very  much,  both  in  health  and  disease. 

2363.  Urine  is  quickly  decomposed  spontaneously  ; and  as  the 


*Jour.  dc  Pkarm.  March,  1S39,  and  Edin.  Philos.  Mag.  Aug.,  1839. 
t See  Thomson  in  Rec.  of  Gen.  Sci.  ii.  3.  1 1.0138,  Thomson. 


Urinary  Calculi. 

urea  is  resolved  into  carbonate  of  ammonia,  phosphate  of  lime  and  Sect,  ix. 
phosphate  of  ammonia  and  magnesia  are  deposited. 

2364.  From  disease  the  urine  is  often  much  changed  in  its  quali- 
ties ; the  following  are  the  principal  alterations. 

2365.  The  urine  often  becomes  so  loaded  with  different  materials,  Deposition 
that  much  is  deposited  in  the  solid  form  before  it  is  discharged,  ofCalculi, 
giving  rise  to  the  production  of  urinary  sand  or  calculi,  according  to 

the  cohesion  of  the  precipitated  matter. 

2366.  Uric  Acid  Calculi  are  of  a brownish-yellow  colour,  and  ge- 
nerally consist  of  different  layers  of  acid.  They  are  decomposed  by  Unc  acid' 
heat,  soluble  in  potassa,  produce  purpurate  of  ammonia  by  nitric  acid. 

In  most  calculi,  small  portions  of  uric  acid  may  be  detected.  An 
excess  of  uric  acid,  or  the  decomposition  of  urate  of  ammonia  by 
other  acids,  are  considered  the  principal  causes  of  the  deposition  of 
uric  acid. 

2367.  Urate  of  Ammonia  Calculi  have  a clay  colour  ; evolve  am-  Urate  of 
monia  when  heated  with  potassa.  With  the  other  agents  mentioned  ammonia, 
in  the  preceding  paragraph,  the  same  phenomena  are  produced  as 

with  uric  acid  calculi. 

2368.  Oxalate  of  Lime  Calculi  are  rough  and  tuberculated  on  the  Oxalate  of 
surface.  Healed  to  dull  redness  they  produce  carbonate  of  limeHime> 
Heated  to  whiteness  nothing  is  left  but  quicklime.  With  sulphuric 

acid,  sulphate  of  lime  is  formed,  and  then  the  oxalic  acid  may  be  se- 
parated in  solution  by  water. 

2369.  Phosphate  of  Lime  Calculi.  Not  decomposed  by  heat ; phosphate 
insoluble  in  potassa;  soluble  in  diluted  nitric  or  hydrochloric  acid;  of  lime, 
give  no  ammonia  when  heated  with  potassa  ; not  dissolved  by  cold 

acetic  acid. 

2370.  Phosphate  of  Ammonia  and  Magnesia  Calculi  evolve  am-  phosphate 
monia  wThen  heated  alone,  or  with  potassa.  Not  dissipated  by  heat,  a™™°* 
though  the  ammonia  is  expelled.  Soluble  in  diluted  nitric  and  hy-  Magnesia, 
drochloric  acids  ; soluble  also  in  cold  acetic  acid. 

2371.  The  Fusible  Calculus  is  a mixture  of  phosphate  of  lime  Fusible, 
with  phosphate  of  ammonia  and  magnesia.  It  is  melted  by  heat. 

Cold  acetic  acid  dissolves  the  phosphate  of  ammonia  and  magnesia, 
but  does  not  affect  the  phosphate  of  lime. 

2372.  The  Carbonate  of  Lime  Calculus  is  distinguished  in  the  Carbonate 
same  manner  as  common  carbonate  of  lime.  A portion  of  animal  of  lime, 
matter  is  generally  blended  with  it.  A calculus  composed  of  oxalate 

and  carbonate  of  lime  has  lately  been  noticed.  Both  these  varieties, 
however,  are  extremely  rare. 

2373.  The  Alternating  Calculus  consists  of  alternate  layers  of  Alterna_ 
some  of  the  preceding  calculi.  Siliceous  Gravel  has  occasionally  ting, 
been  noticed  in  some  urinary  complaints.  It  is  not  affected  by  heat, 

is  insoluble  in  acids,  fuses  with  alkalies  added  in  excess,  and  pro- 
duces silicated  potassa. 

2374.  Cystic  Oxide  Calculi  contain  a peculiar  animal  matter,  cys- Cystic  ox- 

tic  oxide,  which  is  soluble  in  acids,  alkalies,  alkaline  carbonates,  and  ide> 
lime-water.  Xanthic  Oxide  Calculi  consist  of  another  peculiar  ani- 
mal matter.  With  nitric  acid  it  produces  a lemon-yellow  coloured 
compound.  . 

2375.  Fibrinous  Calculi  are  composed  of  fibrin.  The  last  three  ^2][-ous 

64 


506 


Organic  Chemistry — Mdenda. 


Addenda. 


Production 
of  Sugar, 
Albumen, 
&c. 


Urea  de- 
tected. 


varieties  of  calculi  are  extremely  rare,  and  are  decomposed  by  heat, 
in  the  same  manner  as  other  animal  substances. 

2376.  The  uric  acid  and  the  phosphate  of  ammonia  and  magnesia 
calculi,  are  those  most  frequently  observed. 

2377.  Sugar  is  found  in  considerable  quantity  in  the  urine  of  in- 
dividuals affected  with  diabetes ; 6 per  cent,  of  sugar  may  often  be 
procured  from  it.  Kane  obtained  a still  larger  quantity.  Albumen 
is  often  found  in  large  quantity  in  the  urine  of  individuals  affected 
with  some  varieties  of  dropsy,  coagulating  when  exposed  to  heat  like 
the  serum  of  the  blood.  In  some  cases  it  has  coagulated  even  within 
the  bladder. 

2378.  Urea  is  sometimes  found  in  excess  in  urine.  Prout  states, 
that,  when  this  is  the  case,  nitric  acid  added  in  an  equal  bulk  to  a 
few  drops  of  urine  in  a watch-glass,  produces  a crystalline  precipi- 
tate of  nitrated  urea  in  half  an  hour.  Healthy  urine  produces  it 
more  slowly.  It  is  not  absent  in  diabetic  urine,  as  was  at  one  time 
supposed. 

2379.  In  some  diseases  of  the  liver,  the  urine  becomes  tinged 
with  bile,  and  has  a deeper  yellowish  tint  than  usual.  Hydrochloric 
acid  produces  a green  tint  in  urine  charged  with  bile.  r.  179. 


ADDENDA, 

. . Radiation  of  Caloric . The  late  experiments  of  Melloni  have  af- 
of^aloric.  f°rded  results  which  do  not  confirm  the  deductions  of  Leslie  (215)  in 
regard  to  the  influence  of  the  state  of  surfaces  upon  radiation.  A 
square  vessel  was  made  out  of  a block  of  marble,  the  sides  of  which 
were  of  uniform  thickness,  and  the  external  surfaces  were  differently 
prepared.  The  first  was  smooth  and  brilliant ; the  second  was 
equally  smoth,  but  unpolished,  and  tarnished  ; the  third  was  streaked 
in  one  direction ; and  the  fourth  in  two,  crossed  at  right  angles. 
The  vessel  was  then  filled  with  hot  water,  and  projected  the  same 
quantity  of  radiating  caloric  from  each  of  the  four  sides.  Experi- 
ments with  metallic  surfaces  were  attended  with  a much  more  abun- 
dant emission  of  caloric  from  streaked  surfaces  than  from  polished ; 
this  is  attributed  by  Melloni  to  a change  of  hardness  or  density,  in 
consequence  of  the  mechanical  compression.  A surface  of  cast  silver 
had  nearly  one  third  more  radiating  power  than  one  of  the  same  me- 
tal forged,  and  the  radiating  power  of  the  latter  was  increased  four 
fifths  by  roughening  with  emery,  while  that  of  the  former  was  dimin- 
ished nearly  one  fifth. ^ 

Influence  of  Influence  of  Colour  on  Absorption  of  Odours.  Some  important  ob- 
colour  on  seryations  have  been  made  by  Starkt  on  the  influence  of  colour  on 
of  Odours*  t^le  absorption  and  disengagement  of  odorous  matters.  He  found 
that  white  bodies  are  the  least  absorbent,  and  dark  the  most  so  ; and 
has  made  several  important  applications  of  the  results  of  his  experi- 


* Edin.  Philos.  Jour.  xxvi.  299. 


+ Phil.  Trans.  1833. 


Addenda . 507 

ments  in  respect  to  clothing,  white-washing,  the  retention  of  noxious  Addenda. 
effluvia  by  different  coloured  bodies,  and  the  consequent  communica- 
tion of  disease. 

Compound  Blow-pipe.  The  notice  of  Hemming’s  safety  tube  was  Compound 
inserted  (128)  after  the  apparatus  had  been  subjected  to  severe  blow-pipe, 
trials,  the  results  of  which  fully  warranted  its  recommendation  as  a 
valuable  addition  to  the  compound  blow-pipe.  Since  then  an  explo- 
sion of  the  mixed  gases  has  occurred  in  a strong  copper  globe  to 
which  the  safety  tube  was  attached.  The  tube  being  uninjured  and 
still  arresting  explosion  as  perfectly  as  before,  the  cause  of  the  occur- 
rence cannot  be  attributed  to  its  imperfection  ; while  it  furnishes  ad- 
ditional caution  not  to  mix  the  gases  prior  to  their  combustion.  The 
student  should  also  bear  in  mind  that  explosion  may  occur,  even 
when  the  gases  are  contained  in  separate  vessels,  from  unequal 
pressure  ; an  accident  which  Dr  Torrey  informs  me  he  has  experi- 
enced, the  jet  becoming  clogged  at  the  outlet,  and  a portion  of  the  gas 
under  the  greatest  pressure  being  forced  into  the  vessel  containing 
that  under  less  pressure.  This,  however,  can  never  occur  when  the 
double  concentric  jet  (Fig.  129),  as  contrived  by  me,  is  used,  the 
two  orifices  of  the  conical  extremity  being  in  the  same  plane — in  the 
jet  where  the  two  orifices  open  into  one  common  outlet,  (as  in 
Fig.  128  e,)  the  accident  may  occur. ^ 

Photographic  Drawing . Paper  may  be  prepared  with  a solution  p^otogra- 
of  bichromate  of  potassa,  instead  of  the  silver  salt  (1247),  which  phic  draw- 
acquires  a deep  orange  tint  on  exposure  to  the  sun.  The  paper  should  inS- 
be  well  soaked  in  the  saturated  solution  of  the  salt,  dried  rapidly  at  a 
brisk  fire,  excluding  it  from  day-light.  Paper  thus  prepared  is 
sufficiently  sensitive  for  taking  copies  of  prints,  dried  plants,  &c. 

The  portion  covered  by  the  object  retains  the  original  bright  yellow 
tint,  and  the  object  is  represented  yellow  upon  an  orange  ground. 

To  fix  the  drawing,  it  is  to  be  carefully  immersed  in  water,  by  which 
the  portions  of  the  salt  that  have  not  been  acted  upon  by  the  light  are 
dissolved  out,  while  those  which  have  been  exposed  to  it  are  fixed  in 
the  paper.  The  object  then  appears  white  upon  an  orange  ground. 

A pleasing  variety  may  be  made  by  using  sulphate  of  indigo  with 
the  bichromate  of  potassa,  the  colour  of  the  object  and  of  the  paper 
being  then  of  different  shades  of  green. t 

A method  of  fixing  images  of  objects  upon  metal  has  been  recently  £)aguer,.e>s 
made  known  by  Daguerre.  A plate  of  silvered  copper,  well  cleaned  method, 
with  dilute  nitric  acid,  is  exposed  to  the  vapour  of  iodine,  and  an  ex- 
tremely thin  coating  of  iodide  of  silver  is  formed.  Several  precau- 
tions are  required  to  render  the  coating  uniform,  the  chief  of  which 
is  the  use  of  a rim  of  metal  round  the  plate.  The  prepared  plate  is 
placed  in  a camera  obscura  and  allowed  to  remain  from  eight  to  ten 
minutes.  It  is  subsequently  exposed,  at  an  angle  of  48°,  to  the  va- 
pour of  mercury,  and  when  it  has  been  heated  to  167°  F.  the  images 
appear.  The  plate  is  then  exposed  to  the  action  of  hyposulphite  of 
soda  and  finally  washed  in  a large  quantity  of  distilled  water.! 


* See  an  account  of  this  explosion  in  Amer.  Jour,  xxxvii,  104. 
t Ponton  in  Trans.  Soc.  Arts,  Scotland , May,  1839. 
tSee  Jour.  Franklin  Inst.  xxiv.  207. 


608 


Addenda . 


Addenda. 

Detection 
of  Iodine 
and  Bro- 
mine. 


Oxide  of 
Phospho- 
rus. 


Detection  of  Iodine  and  Bromine.  Schweitzer  has  very  recently 
described  a method  of  ascertaining  the  proportion  of  iodine  and  bro- 
mine in  water,  by  which  he  obtained  from  100,000  grs.  of  the  water 
of  the  Congress  spring  of  Saratoga  0.12164  gr.  of  iodide  of  silver, 
representing  in  1000  grs.  of  the  water  0.00067  gr.  of  iodine. 
Schweitzer  recommends  an  ammoniacal  solution  of  chloride  of  silver, 
prepared  by  mixing  one  part  of  a saturated  solution  of  recently  pre- 
cipitated chloride  of  silver  in  ammonia  with  one  of  liquid  ammonia 
(sp.  gr.  0.935)  and  two  parts  water.  If  to  a concentrated  solution  of 
chloride  of  sodium  containing  one  thirtieth  part  of  a bromide,  a few 
drops  of  this  solution  be  added,  the  solution  of  chloride  of  sodium 
will  remain  clear,  but  if  the  most  minute  particle  of  an  iodide  be 
present,  it  will  be  rendered  turbid.  For  the  method  of  examination 
for  bromine,  and  of  analysing  sea-water,  see  Bond,  and  Edin.  Phil. 
Mag.  July,  1839. 

The  quantity  of  iodine  in  sea-water  is  very  minute,  174  pounds 
Troy  not  containing  one  grain. 

The  following  is  a comparative  analysis  of  sea-water  : 


Water 

Chloride  of  sodium 
“ potassium 
“ magnesium 

Bromide  of  magnesium 
Sulphate  of  magnesia  - 
“ lime  - 

Carbonate  of  lime 


On. 

Grs. 

964.74372 

. 

. 

959.26 

- 27.05948 

. 

27.22 

0 7' 

. 

. 

0.01 

- 3 CG658 

. 

6.14 

0.02929 

. 

. 

— 

- 2.29578 

. 

* 7.02 

1.40662 

. 

. 

0.15 

- 0.03301  J 

Carbonate  of  lime 
and  magnesia. 

i 

0.20 

1000.00000 

1000.00 

Very  beneficial  results  in  scrofulous  diseases  are  stated  by 
Schweitzer  to  have  followed  from  the  internal  and  external  use  of 
the  waters  of  several  saline  springs  in  Germany,  concentrated  by 
evaporation. 

Oxide  of  Phosphorus.  M.  Botger  has  found  that  sulphuret  of 
carbon  is  the  best  solvent  of  phosphorus,  dissolving  20  parts  at  mean 
temperature,  while  the  oxide  of  phosphorus  is  not  acted  upon  by  it. 
To  separate  the  oxide  he  directs  to  put  the  impure  oxide,  obtained  by 
combustion,  into  a large  bottle,  pour  sulphuret  of  carbon  upon  it  with 
an  equal  measure  of  absolute  alcohol ; cork  the  bottle,  and  shake  it 
well  for  about  a minute,  then  allow  the  oxide  to  subside,  and  pour  ofF 
the  phosphorized  liquor  ; repeat  this  operation  with  a fresh  portion 
of  the  sulphuret  and  alcohol,  and  then  put  the  oxide  of  phosphorus 
on  a filter,  and  wash  it  first  with  alcohol,  and  then  with  water;  after 
this  dry  it  by  exposure  to  the  air,  or,  what  is  better,  under  a receiver  • 
with  sulphuric  acid. 

The  product  resists  combustion  at  a high  temperature  ; with  chlo- 
rate of  potassa  it  produces  a strongly  detonating  powder,  violent 
explosion  taking  place  even  during  mixture  without  much  pressure. 
According  to  Pelouze,  the  oxide  obtained  by  combustion  and  purified 
by  distillation,  is  P3-f-0,  while  that  procured  by  the  decomposition 
of  the  chloride  (565  note)  consists  of  P4-|“0.t 


* By  Schweitzer.  t By  Laurens. 

t Jour,  de  Pharm.  Feb.,  1839,  and  Lond.  and  Edin.  Phil.  Mag.  July,  1839. 


Addenda. 


509 


Detection  of  Nitric  Acid.  Richemont  has  proposed  a method  of  Addenda, 
much  delicacy  of  detecting  nitric  acid,  depending  on  the  fact  that  a Detection 
mixture  of  a concentrated  solution  of  protosulphate  of  iron  and  sul- of  nitric 
phuric  acid  becomes  rose-red  by  the  addition  of  deutoxide  of  nitro-acicl* 
gen,  or  purple,  if  the  latter  is  present  in  larger  proportion ; the 
quantity  of  the  deutoxide  required  is  so  small,  that  an  exceedingly 
minute  portion  may  be  detected  by  it.  A small  quantity  of  sulphuric 
acid  is  added  to  the  solution  to  be  examined,  the  latter  being  equal 
to  three  fourths  of  the  bulk  of  the  former.  When  the  mixture  has 
cooled,  drop  in  a concentrated  solution  of  protosulphate  of  iron, 
which,  if  any  nitric  acid  is  present,  decomposes  it,  causing  the  evo- 
lution of  nitric  oxide,  which  produces  the  rose-red  or  purple  tint. 

This  mode  of  operating  detects  one  part  of  nitric  acid  in  24.000  of 
water.^ 

Detection  of  Nitrogen.  Mix  the  gas  under  examination  with  Detection 
from  3 to  6 times  its  volume  of  a mixture  of  oxygen  and  hydrogen  of  nitroSen* 
(in  equal  vols.),  and  detonate  the  whole  in  a eudiometer  by  the  elec- 
tric spark.  Mix  the  fluid  that  bedews  the  eudiometer  after  the 
explosion  with  sulphuric  acid,  to  which  a few  drops  of  protosulphate 
of  iron  in  solution  have  been  added,  the  fluid  will  assume  the  rose- 
red  tint  if  the  minutest  portion  of  nitrogen  is  present.  It  is  of 
course  necessary  to  avoid  any  source  of  fallacy  arising  from  the  pre- 
sence of  atmospheric  air  in  the  oxygen  and  hydrogen  employed.! 

Indelible  Ink.  A solution  of  the  gluten  of  wheat  in  pyroligneous  Traill’s  in- 
aoid,  has  been  recommended  by  Traill,  as  an  indelible  ink.  He  dj.  delible  mk. 
rects  the  gluten  to  be  separated  from  the  starch  as  completely  as  pos- 
sible, and  when  recent  to  be  dissolved  in  the  acid  with  the  aid  of 
heat.  This  forms  a saponaceous  fluid  which  is  to  be  tempered  with 
water  until  the  acid  has  the  usual  strength  of  vinegar.  Each  ounce 
of  the  fluid  is  then  to  be  ground  with  from  8 to  10  grains  of  the  best 
lamp-black,  and  1J  gr.  of  indigo.! 

Salts  of  Baryta  and  Strontia.  According  to  Smith  these  salts  Salts  of 
are  distinguished,  by  the  action  of  chromate  of  potassa  and  acetic  baryta  and 
acid.  It  is  only  necessary  to  add  to  a solution  of  the  salt,  a solution  strontia* 
of  chromate  of  potassa,  which,  if  baryta  be  present,  will  produce  a 
light  yellow  precipitate  insoluble  in  acetic  acid.  This  reagent  will 
also  serve  to  distinguish  baryta  from  lime.§ 

Ethyle.  When  small  pieces  of  potassium  are  placed  in  a glass  Ethyle. 
tube  3 to  5 lines  wide,  containing  chloride  of  ethyle,  a powerful  ac- 
tion ensues,  and  the  metal  becomes  covered  with  a white  crust, 
which  should  be  broken  up  so  as  to  cause  a fresh  metallic  surface  to 
be  exposed  to  the  action  of  the  fluid.  The  mixture  soon  begins  to 
boil,  and  chloride  of  ethyle  distils  over.  A tube  bent  at  right  angles 
should  be  fixed  in  the  mouth  of  the  large  one  to  connect  it  with  a 
receiver  kept  cool  by  a freezing  mixture.  If  sufficient  chloride  of 
ethyle  is  present,  all  the  potassium  is  converted  into  the  white  crust, 
which  is  dissolved  by  water  with  the  disengagement  of  hydrogen 


k,  * Lond.  and  Edin.  Phil.  Mag.  xiii.  393.  t Richemont,  Ibid, 

t Edin.  Philos.  Jour.  xxv.  213- 

§ J.  L.  Smith,  in  Amer.  Jour,  xxxvi.  183.  See  also  a method  by  Rose,  in  Lond. 
and  Edin.  Phil.  Mag.  Jan.,  1839. 


510 


Mdtnda. 


Addenda. 


Disastase. 


Dextrine. 


gas.  On  agitating  the  watery  solution  with  ether  and  decanting  the 
ethereal  solution,  a volatile  oily  fluid  is  obtained  by  evaporating  in 
vacuo  at  a low  temperature.  This  fluid  burns  vividly,  has  a peculiar 
odour,  and  very  acrid  taste. 

The  white  powder  consists  of  C4H5.  From  these  experiments 
Lo  wig  concludes,  that  by  the  action  of  potassium  on  chloride  of  ethyle, 
chloride  and  ethylide  of  potassium  are  formed,  the  latter  combination 
being  decomposed  by  the  action  of  water,  setting  free  the  ethyle, 
either  pure  or  as  a hydrate.* 

Diastase , is  the  name  given  lo  a substance  extracted  from  malted 
barley,  and  which  may  be  applied  to  important  purposes  in  domestic 
economy.  It  is  obtained  by  macerating  the  ground  malt  in  cold  water 
for  some  time.  It  is  then  pressed  and  the  liquid  filtered,  and 

heated  to  158°.  The  coagulated  portion  is  separated  and  the 
liquid  being  again  filtered  is  mixed  with  a sufficient  quantity  of  al- 
cohol to  throw  down  the  diastase,  the  diastase  is  again  dissolved  in 
water  and  thrown  down  by  alcohol,  and  this  is  to  be  repeated  several 
times. 

Diastase  is  solid,  white,  insoluble  in  water,  but  soluble  in  dilute 
alcohol.  Its  solution  separates  amidin  from  all  starchy  substances 
containing  it,  hence  its  name.t  It  exists  in  the  seeds  of  malted 
barley,  oats  and  wheat.  One  part  is  sufficient  to  render  soluble  the 
interior  portion  of  two  thousand  parts  of  starch,  and  to  convert  it  into 
sugar. 

To  prepare  it  upon  a large  scale,  850  lbs.  of  water  are  heated  to  86°, 
10  parts  of  ground  malt  are  then  added  and  the  heat  raised  to  140° ; 
220  lbs.  of  flour  are  then  added  and  the  whole  well  mixed.  When 
the  temperature  has  risen  to  158°  we  should  endeavour  to  keep  it 
steady  at  that  point,  or  at  least  not  to  allow  it  to  cool  below  150°, 
nor  to  rise  above  167°.  In  twenty  minutes  the  liquid  becomes  more 
transparent,  and  from  being  viscid  and  thready  at  first,  it  becomes 
almost  as  fluid  as  water.  When  this  happens  the  temperature 
should  be  suddenly  raised  to  212°.  The  whole  is  then  left  at  rest, 
the  clear  portion  drawn  ofF,  filtered  and  evaporated  by  means  of 
steam  at  230°,  the  scum  being  removed.  When  sufficiently  concen- 
trated, it  is  poured  into  a receiver  of  tin  plate  or  wood,  and  on  cool- 
ing it  coagulates  into  an  opaque  jelly. 

While  hot,  if  it  be  mixed  with  yeast  and  kneaded  into  the  dough  ; 
it  serves  well  for  the  preparation  of  bread. 

If  spread  out  in  thin  layers  and  dried  in  the  air,  or  by  a stove,  we 
obtain  dextrine , which  being  reduced  to  powder,  may  be  introduced 
into  all  kinds  of  pastries,  chocolate,  bread,  &c.t 

Dextrine  dissolved  in  diluted  alcohol  has  been  lately  recommended 
as  a temporary  varnish  for  oil  paintings,  preventing  the  imbibition  of 
colours,  even  when  employed  a few  days  after  the  finishing  of  the 
picture.  Applied  with  a soft  brush,  it  gives  a clearness  like  a light 
varnish,  which  can  be  removed  by  a moist  sponge,  when,  after  a few 
months,  common  varnish  may  be  applied  with  its  ordinary  effect. 
The  same  solution  serves  as  a perfect  varnish  for  water  colours,  and 


f * Poggendorff,  Ann.  45,  p.  347,  and  Lond.  and  Edin.  Phil . Mag.  July,  1839. 
t From  duaTtjfH,  to  separate.  t T.  Org.  Bod.  666. 


Addenda. 


511 


for  fixing  pencil  and  crayon  drawings.  The  solution  of  dextrine,  in  Addenda. 
about  an  equal  portion  of  warm  water,  furnishes  a paste  which  re- 
mains liquid  and  possesses  great  energy.  It  may  be  advantageously 
used  as  a substitute  for  the  greater  number  of  common  pastes.* 

Nature  of  Ferment , or  Yeast.  The  following  results  have  been 
given  by  M.  Cagnard-Latour.f  Yeast  is  a mass  of  small  globular 
bodies  capable  of  self-reproduction,  and  of  course  oxygenized,  and  yeast, 
not  an  inert  or  purely  chemical  substance.  These  bodies  appear  to 
belong  to  the  vegetable  kingdon,  and  are  generated  in  two  different 
modes.  They  appear  to  act  upon  a solution  of  sugar  as  if  they  were 
alive,  whence  it  may  be  inferred,  that  it  is  in  all  probability  by  some 
effect  of  their  vegetation  that  they  disengage  carbonic  acid  from  this 
solution  and  thus  convert  it  into  a spirituous  liquor. 

In  a valuable  memoir  by  T.  A.  Quevenne,!  the  author  arrives  at 
the  following  conclusions  : — 1st.  Yeast  is  a substance  which  con- 
stantly presents  the  appearance  of  little  globules  of  nearly  uniform 
figures.  2d.  These  globules  appear  to  be  always  of  the  same  nature, 
whatever  their  origin.  3d.  It  is  the  insoluble  constituent  part  of 
these  globules  which  is  apt  to  produce  fermentation,  and  not  the  ex- 
tractive matters  which  accompany  it.  4th.  The  globules  of  yeast 
can  effect  the  decomposition  of  sugar  not  only  at  a temperature  from 
10°  to  30°  or  40°  Cent.  (50°  to  86°  or  104°  F.),  but  even  at  the  heat 
of  boiling  water ; but,  with  this  difference,  that  at  a temperature  in- 
ferior to  50°  they  transform  the  sugar  into  alcohol  and  carbonic  acid, 
while  above  50°  (=  122°  F.),  alcohol  appears  not  to  be  formed  ; the 
only  gas  obtained  in  either  case  is  carbonic  acid.  5th.  Yeast,  du- 
ring the  alcoholization  of  sugar,  undergoes  a thorough  modification. 

It  loses  all  its  nitrogen,  which  goes  to  form  ammonia,  by  which 
means  its  fermentative  power  is  completely  exhausted.  6th.  The 
globular  aspect  of  yeast,  and  its  principal  chemical  properties,  are 
sufficient  to  induce  us  to  regard  it  as  an  organic  substance  of  new 
formation ; and  hence  fermentation  ought  not  to  be  considered 
merely  as  a decomposition,  but  simply  as  a modification  which  gives 
birth  at  one  and  the  same  time  to  products  both  organic  and  inorganic. 

7th.  The  circumstances  under  which  fermentation  takes  place,  and 
the  phenomena  which  accompany  it,  and  the  influence  which  a great 
number  of  bodies  have  over  the  progress  of  the  operation,  are  of  a 
nature  to  induce  the  belief  that  it  is  actually  owing  to  a sort  of  vege- 
tation, but  this  proposition  requires  additional  proofs 

Respiration  of  Plants.  Edwards  and  Colin  have  instituted  expe-Reg  irat-on 
riments  upon  the  respiration  of  plants  from  which  they  have  drawn  o/pfaSs.0 
the  following  results  : — 1st,  that  water  is  decomposed  ; 2d,  that  the 
oxygen  of  the  decomposed  portion,  unites  with  the  carbon  of  the  seed, 
and  forms  carbonic  acid  gas  ; 3d,  that  this  carbonic  acid  disengages 
itself  from  the  seed,  in  whole  or  in  part ; and  4th,  the  other  portion 
of  the  decomposed  water,  the  hydrogen,  is  absorbed  by  the  seed,  in 
whole  or  in  part.  They  also  infer  frdm  their  experiments  that  re- 
spiration is  not,  as  it  has  been  hitherto  considered,  solely  a function 
of  excretion.il 

* Jour.  Franklin  Inst.  xxiv.  114.  t Comptes  rendus  de  Vlnstit.,  1837,  906. 

t Jour,  de  Pharm.  Juilliet,  1888.  § See  Jour.  Franklin  Instil,  xxiii.  119. 

||  Ann.  des.  Sci.  Nat.  Dec,,  1838,  and  Edin.  Philos.  Jour.  July,  1839. 


512 


Addenda. 


Addenda. 

New  com- 
pound of 
Dicyanide 
with  binox- 
ide  of  mer- 
cury. 


Preserva- 
tion of  po- 
tassium. 


Emulsin. 


New  compound  of  Bicyanide  with  Binoxide  of  Mercury.  When 
dilute  hydrocyanic  acid  is  digested  on  red  oxide  of  mercury,  in  ex- 
cess, a white  nearly  insoluble  compound  is  formed,  which  may  be 
separated  from  any  soluble  bicyanide  which  may  be  present  in  the 
supernatant  liquid  by  collecting  it  on  a filter.  Boiling  water  dis- 
solves the  new  compound,  and  leaves  the  excess  of  oxide  of  mercury. 
On  cooling,  the  salt  is,  in  a great  measure,  deposited  on  the  sides  and 
bottom  of  the  vessel  in  minute,  pure,  white,  transparent,  prismatic 
needles.  This  salt  is  anhydrous,  its  solution  has  an  alkaline  reac- 
tion, and  it  consists  of  equal  atoms  of  the  two  mercurial  compounds, 
or  it  is  (HyCy2-f-Hy02).  When  heated  in  a tube,  it  decomposes 
with  a slight  detonation,  giving  off  carbonic  acid,  nitrogen,  cya- 
nogen, and  metallic  mercury,  leaving  a black  residue  (para-cyano- 
gen.) Neutralized  by  nitric  acid,  it  gives  a beautiful  salt  in  long, 
delicate,  quadrangular  prisms,  which  are  represented  by  HyCy2-[- 
(Hy02+iN05),  and  are  very  soluble  in  water.  It  gives  also  with 
acetic  acid,  a crystalline  compound,  in  which  the  quantity  of  acid 
appears  to  exist  in  a still  smaller  proportion.  With  acid  nitrate  of 

silver,  it  gives  Wohler’s  salt  (HgCy2-f-AgN-{-4H),  nitrate  of  mercu- 
ry remaining  in  solution.  With  neutral  nitrate  of  silver  and  vari- 
ous other  salts,  it  gives  crystalline  compounds.* 

Preservation  of  Potassium.  Dr  Gale  has  stated  that  the  oil  of 
copaiva  contains  oxygen,  which  renders  it  liable  to  convert  potassium 
into  potassa,  forming  with  it  a peculiar  species  of  soap;  from  ex- 
periments made  upon  several  specimens  of  the  balsam,  the  oil  ob- 
tained from  them  afforded  similar  results,  and  he  is  of  opinion  that 
no  substance  hitherto  used  will  supply  the  place  of  naphtha.! 

Emulsin.  The  following  process  has  been  employed  for  obtain- 
ing emulsin , by  Thomson  and  Richardson.  Sweet  almonds  were 
triturated  in  a mortar  and  small  portions  of  water  gradually  added 
until  a milky  fluid  was  obtained.  This  fluid  was  mixed  with  four 
times  its  vol.  of  ether  and  frequently  agitated  so  as  to  effect  an  in- 
timate mixture.  A clear  fluid  gradually  separated  at  the  bottom  of 
the  stoppered  bottle  in  which  the  experiment  was  made,  which  in 
the  course  of  three  weeks  was  drawn  off  by  means  of  a syphon.  The 
fluid  was  filtered,  and  to  one  half  of  the  clear  solution  a large  quan- 
tity of  alcohol  was  added  ; a copious  precipitation  of  white  flocks 
ensued  ; these  were  emulsin.  Washed  with  alcohol,  and  dried  over 
sulphuric  acid  in  the  vacuum  of  an  air  pump,  it  was  obtained  in  the 
state  of  a white  powder,  without  taste  or  smell,  soluble  in  water,  in- 
soluble in  alcohol  and  ether.  Its  analysis  gave  the  relation  of  the 
carbon  and  nitrogen  as  6COa:  IN  or  3C:  IN.  When  boiled  with 
baryta,  ammonia  was  disengaged,  and  from  the  experiments  it  was 
inferred  to  be  an  amide,  and  the  salt  formed  with  baryta  to  be  a com- 
pound of  baryta  and  emulsic  acid.  The  authors  are  inclined  to  infer 
that  fibrin,  gelatin,  casein,  &c:  are  all  amides.! 


* Johnston  in  Eighth  Report  of  British  Association,  69. 

+ Amcr.  Jour.  xxi.  64.  t Eighth  Report  of  British  Assoc.  48. 


APPENDIX. 


Chemical  Formula.  Various  changes  have  been  made  in  chemical  formulge.  Thus 
Berzelius  now  uses  HO,  KO,  FeS,  instead  of  H+O,  K+O,  Fe+S,  for  water,  potassa,  and 
sulphuret  of  iron. 

The  formula  for  apophyllite  is  now  8 Ca  Si  + KS*  + 16  aq ; the  8 denoting  8 eq.  of 

CaSi,  or  silicate  of  lime,  which  are  united  with  1 eq.  of  bisilicate  of  potassa,  and  16  of  water. 

The  system  of  Liebig  and  Poggendorff  is  based  upon  the  following  principles.  Numbers 
are  placed  below  and  to  the  right  of  the  symbols  which  affect  those  to  which  they  are  at- 
tached. Numbers  are  placed  before  the  symbols  which  affect  all  that  follow  as  far  as  the 
next  full  stop  or  sign  of  addition.  A figure  placed  before  a parenthesis  applies  to  all  con- 
tained within  it.  The  same  compound  may  therefore  be  written  in  different  ways.  Thus 

the  constitution  of  a crystal  of  alum  is  represented  by  KS  T A ISs  + 24H,  or  KO, 
SO;?  -1-  AI2O3,  3S03  -f  24  aq. 

To  distinguish  water  in  different  states  of  combination  Liebig  and  Poggendorff  propose 
to  express  water  of  crystallization  by  aq.  When  the  water  is  more  powerfully  retained 
and  the  compounds  are  more  permanent,  or  in  the  state  of  hydrates , the  water  is  denoted  by 
an  h attached  to  the  symbol  of  the  substance  containing  it.  Thus  A being  the  symbol  of 
acetic  acid,  Ah  is  the  symbol  of  the  hydrate;  MsO,M|,  + 4 aq.  denotes  the  malate  of 
magnesia  and  5 eq.  of  water,  but  distinguishes  4 of  these  as  water  of  crystallization,  while 
the  fifth  is  united  with  the  malic  acid  and  forms  with  it  a hydrate.  The  symbol  HO  is 
used  in  doubtful  cases,  and  when  changes  effected  by  chemical  action  are  explained.  L. 
and  T.  240. 

Wollastons  Synoptic  Scale  of  Chemical  Equivalents*  The  scale  consists  of  a moveable 
slider  with  a series  of  numbers  upon  it,  from  10  to  320,  on  each  side  of  which  and  on  the 
fixed  part  of  the  scale,  are  set  down  the  names  of  various  chemical  substances. 

The  scale  is  founded  on  the  constancy  of  composition  in  chemical  compounds  (106) ; the 
equivalent  power  of  the  quantities  that  enter  into  combination  (108);  and  the  proper- 
ties of  a logometric  scale  of  numbers. 

The  numbers  are  so  arranged,  that  at  equal  intervals  they  bear  the  same  proportion  to 
each  other.  The  student  will  easily  observe  and  understand  this,  by  measuring  a few  dis- 
tances upon  the  scale  with  a pair  of  compasses,  or  even  a piece  of  paper.  If  his  paper 
extend  from  10  to'20,  it  will  also  extend  from  20  to  40,  or  from  55  to  110,orfrom  160  to  320. 
Whatever  number  is  at  the  upper  edge  of  the  paper  will  be  doubled  at  the  lower.  If  any 
other  distance  be  taken,  the  same  effect  will  be  observed.  If,  for  instance,  the  paper  ex- 
tends from  10  to  14,  then  any  other  two  numbers  found  at  its  upper  and  lower  edge  will 
be  in  the  same  proportion  as  these  two  numbers  10  and  14.  Thus  make  the  upper  number 
100,  and  the  lower  number  will  be  140. 

Now  supposing  that  the  paper  were  cut  of  such  a width  that,  one  of  its  edges  being  ap- 
plied upon  the  scale  to  the  number  representing  the  equivalent  of  one  body,  the  other 
should  coincide  with  the  number  of  the  equivalent  of  a second  body ; then  upon  moving 
the  paper,  wherever  it  was  placed  over  the  numbers,  those  at  its  upper  and  lower  edges 
would  still  represent  the  corresponding  proportional  quantities  of  the  two  bodies  as  accu- 
rately as  at  first,  because  the  numbers  at  equal  distances  on  the  scale  are  proportional  to 
each  other.  Thus  suppose  the  upper  edge  were  made  to  coincide  with  40  and  the  lower 


* The  paper,  by  its  author,  describing  the  scale  is  inserted  in  the  Philosophical  Transactions 
for  1814. 


65 


514  Appendix. 

with  78,  then  the  upper  edge  might  be  called  sulphuric  acid,  and  the  lower  baryta  ; and 
this  width  once  ascertained,  the  paper  wherever  applied  upon  the  scale,  would  shew  at  its 
lower  edge  the  quantity  of  baryta  necessary  to  combine  with  the  quantity  of  sulphuric 
acid  indicated  by  its  upper  edge 

It  is  evidently  of  no  consequence  whether  the  paper  be  moved  up  and  down  over  the 
the  scale,  or  the  line  of  numbers  be  moved  higher  and  lower,  to  bring  its  different  parts  to 
the  edges  of  the  paper.  And  supposing  the  piece  of  paper  just  described  to  be  pasted 
upon  the  side  of  the  scale,  then  by  moving  the  latter  any  of  the  numbers  might  be  made  to 
coincide  with  the  upper  oi  lower  edge  at  pleasure,  and  consequently  the  quantity  of  sul- 
phuric acid  necessary  to  combine  with  any  quantity  of  baryta,  and  vice  versa,  ascertained 
by  mere  adjustment  and  inspection  of  the  scale  Or  if,  instead  of  referring  to  the  separate 
piece  of  paper,  marks  were  to  be  made  on  the  side  of  the  scale  at  40  and  78,  and  named 
sulphuric  acid  and  baryta,  the  same  object  would  be  attained,  and  the  same  method  of  in- 
quiry rendered  available. 

Other  substances  are  to  be  put  down  upon  the  scale  exactly  in  the  same  manner.  Thus 
the  scale  being  adjusted  until  the  number  40  coincides  with  the  sulphuric  acid  already 
marked,  then  sulphate  of  baryta  is  to  be  written  at  118,  and  thus  its  place  is  ascertained; 
nitrate  of  baryta  at  1312 ; soda  at  32  ; sulphate  of  soda  at  72;  and  a similar  process  is  to  be 
adopted  with  every  substance,  the  number  of  which  has  been  ascertained  by  experiment. 
The  instrument,  which  in  this  state  merely  represents  the  actual  numbers  supplied  by  ex- 
periment, will  faithfully  preserve  the  proportions  thus  set  down,  whatever  the  variation  of 
the  position  of  the  slider  may  be.  it  is  therefore  competent  to  change  all  the  numerical 
expressions  to  any  degree  required,  the  knowledge  of  one  only  being  sufficient  first  by  ad- 
justment, and  then  by  inspection  to  lead  to  the  rest, 

A few  illustrations  of  the  powers  and  uses  of  this  scale  will  be  sufficient  to  make  the 
student  perfect  master  of  its  nature  and  applications.  Suppose  that  in  analysing  a mineral 
water,  the  sulphates  in  a pint  of  it  have  been  decomposed  by  the  addition  of  muriate  of 
baryta,  and  the  resulting  sulphate  of  baryta  w ashed,  dried,  and  weighed  : from  its  quantity 
may  be  deduced  the  oxact  quantity  of  sulphuric  acid  previously  existing  in  the  mineral 
water.  Thus,  if  the  sulphate  of  baryta  amount  to  43.4  grains,  the  slider  is  to  be  moved 
until  that  number  is  opposite  to  sulphate  of  baryta,  and  then  at  sulphuric  acid  will  be  found 
the  quantity  required,  namely  14.7  grains.  In  the  same  manner  the  scale  will  give  infor- 
mation of  the  quantity  of  any  substance  contained  in  a given  weight  of  any  of  its  com- 
pounds; these  having  previously  been  deduced  from  experiment,  and  accurately  set  down 
cn  the  table  in  the  manner  just  explained 

If  it  be  desired  to  know  how  much  of  one  substance  must  be  used  in  an  experiment  to 
act  upon  another,  it  is  evident  that  the  equivalent  must  be  taken,  and  this  may  be  learned 
from  the  scale.  Suppose  that  a pound  of  sulphate  of  baryta  has  been  mixed  with  charcoal, 
and  well  heated,  to  convert  it  into  a sulphurct,  and  that  by  the  addition  of  nitric  acid  it  is 
to  be  converted  into  nitrate  of  baryta  The  quantity  of  acid  which  will  probably  be  re- 
quired may  be  learned  by  bringing  100  to  sulphate  of  barvta,  and  then  by  looking  for  the 
number  opposite  nitric  acid  : it  will  be  found  to  be  40.  But  this  represents  the  quantity  of 
dry  acid  : casting  the  eye  therefore  lower  down,  upon  liquid  nitric  acid  of  a specific  gravity  of 
1.50,  it  will  be  found  that  01  lbs.  or  a little  more,  is  the  equivalent  for  10U  lbs.  and  conse- 
quently tint  61  hundredth  parts,  or  somewhat  above  six-tenths  of  a pound  of  such  acid, 
will  bo  sufficient  for  the  pound  of  sulphate  of  baryta  operated  with. 

If  a certain  weight  of  carbonate  of  barvta  be  r quired  in  that  moist  and  finely  divided 
state,  in  which  it  is  obtained  by  precipitation,  and  in  which  it  cannot  be  weighed,  the  accu- 
racy of  tho  quantity  may  be  insured  by  taking  the  equivalent  of  dry  muriate,  or  nitrate 
of  baryta,  precipitating  it  by  an  excess  of  carbonate  of  potassa,  and  then  washing  off  the 
the  salts  which  remain  in  solution.  Suppose  100  grains  of  the  carbonate  were  required; 
by  bringing  that  number  to  carbonate  of  baryta,  it  will  be  found  that  the  quantity  of  dry 
muriate  necessary  will  be  105.8  parts,  and  the  quantity  of  nitrate  133.4  ; and  if  the  quantity 
of  carbonate  of  potassa  necessary  for  this  purpose  be  also  required,  it  will  be  found  oppo- 
site the  name  of  that  substance  on  the  scale,  to  be  a little  less  than  70  parts,  so  that  5 or  10 
parts  more  will  ensure  a satisfactory  excess. 

The  second  paragraph  of  Wollaston’s  description  of  this  scale  may  be  transcribed,  as  a 
further  illustration  of  the  powers  of  the  instrument.  “ If,  for  instance,  the  salt  under  ex- 
amination be  the  common  blue  vitriol,  or  crystallized  sulphate  of  copper,  the  first  obvious 
questions  are — (1)  How  much  sulphuric  acid  does  it  contain?  (2)  How  much  oxide  of 
copper?  (3)  How  much  water?  He  [the  analytic  chemist]  may  not  be  satified  with  these 
first  steps  in  the  analysis,  but  may  desire  to  know  further  the  quantities  (4J  of  sulphur,  (5) 
of  copper,  (6)  of  oxygen,  (7)  of  hydrogen.  As  means  of  gaining  this  information,  he 
naturally  considers  the  quantity  of  various  reagents  that  may  be  employed  for  discovering 
the  quantity  of  sulphuric  acid  (8),  how  much  baryta,  (9)  carbonate  of  baryta,  or  (10)  nitrate 


Appendix.  515 

of  baryta,  would  be  requisite  for  this  purpose  ? (11)  How  much  lead  is  to  be  used  in  the 

form  of  (12)  nitrate  of  lead;  and  when  the  precipitate  of  (13)  sulphate  of  baryta,  or  (14) 
sulphate  of  lead  are  obtained,  it  will  be  necessary  that  he  should  also  know  the  proportion 
which  either  of  them  contains  of  dry  sulphuric  acid.  He  may  also  endeavour  to  ascertain 
the  same  point  by  means  of  (15)  the  quantity  of  pure  potassa,  or  (16)  of  carbonate  of 
potassa  requisite  for  the  precipitation  of  the  copper.  He  might  also  use  (17)  zinc,  or  (18) 
iron  for  the  same  purpose,  and  he  may  wish  to  know  the  quantities  of  (19)  sulphate  of 
zinc,  or  (20)  sulphate  of  iron,  that  will  then  remain  in  the  solution.” 

All  these  questions  and  points  are  answered  by  moving  the  slider  until  the  number  ex- 
pressing the  quantity  operated  with  coincides  with  sulphate  of  copper  crystallized.  5, 
Water.  Let  it  for  instance  be  100  : this  being  brought  opposite  crystallized  sulphate  of  cop- 
per, the  information  relative  to  all  the  above  points,  except  the  sixth  and  seventh,  is  sup- 
plied by  mere  inspection.  The  sixth  may  be  supplied  by  substracting  (5)  the  quantity  of 
copper  from  (2)  the  quantity  of  oxide  of  copper,  or  by  halving  the  quantity  at  2 oxygen, 
or  taking  the  third  of  that  at  3 oxygen.  The  seventh  relates  to  the  quantity  of  hydro- 
gen in  the  5 water  present  in  the  salt;  this  quantity  of  hydrogen  does  not  come  with- 
in the  line  of  numbers,  but  may  easily  be  obtained  by  doubling  the  quantity  of  water, 
or  doubling  the  quantity  of  the  salt  used,  which  will  then  bring  Id  hydrogen  into  the  scale, 
and  the  half  of  this  is  to  be  taken  as  the  quantity  in  5 water,  or  in  100  grains  of  the  salt. 
Putting  therefore  200  to  sulphate  ©f  copper,  10  hydrogen,  is  indicated  as  17  parts  nearly, 
when  of  course  the  half  of  this,  or  8<#  parts  is  the  quantity  in  100  grains  of  the  crystallised 
salt  of  copper. 

Whenever  it  thus  happens  that  the  number  known  or  the  number  sought  for  is  out  of 
the  scale,  then  some  convenient  multiplier  of  the  numbers  may  be  used.  The  most  con- 
venient method  is  to  use  the  tens  or  the  hundreds  as  units,  or  what  is  the  same  thing,  to 
consider  for  the  time  that  decimal  points  are  inserted  between  the  units  and  the  tens,  or 
between  the  tens  and  the  hundreds  of  all  the  numbers  on  the  scale.  Thus  if  it  were 
required  to  ascertain  how  much  magnesia  and  sulphuric  acid  were  contained  in  a pound  of 
crystallized  sulphate  of  magnesia,  no  1 exists  upon  the  scale,  and  of  course  no  fractions  or 
small  parts  of  1 ; but  imagine  decimal  points  between  the  tens  and  the  hundreds,  then  10  upon 
the  scale  becomes  one-tenth,  22  twentytwo  hundredths,  100  one,  220  two  and  two-tenths 
and  so  on.  Bringing  therefore  100  to  crystallized  sulphate  of  magnesia,  it  represents  the 
1 pound,  and  by  inspection  it  will  be  found  that  it  contains  16  hundredths  of  a pound  of 
magnesia,  and  3*2^  hundredths  of  a pound  of  sulphuric  acid. 

As  another  illustration;  suppose  that  the  quantity  of  magnesia  in  50  lbs.  of  crystallized 
Epsom  salt  were  required  ; upon  bringing  50  opposite  the  name  of  the  sail,  the  quantity  of 
magnesia  will  be  found  smaller  than  any  quantity  expressed  upon  the  scale  : but  all  that  is 
necessary  to  obtain  the  answer  is,  to  double  the  quantity  of  the  salt,  and  then  to  halve  the 
quantity  of  magnesia  indicated ; in  which  way  it  will  be  found  that  the  50  lbs.  contain 
about  8 lbs.  of  the  oxide. 

These  Synoptic  scales  are  generally  constructed  of  paper  or  wood.  It  is  almost  impos- 
sible that  they  should  be  accurate,  because  of  the  extension  and  contraction  of  the  paper,  and 
the  facility  with  which  it  yields  to  mechanical  impressions,  and  may  be  stretched  when  in 
a moistened  state.  These  scales  should  never  be  considered  as  accurate  when  they  first 
come  from  the  instrument-maker.  They  may  be  examined  by  a pair  of  compasses  or  a 
a piece  of  paper,  as  before  described  (p.  513),  to  ascertain  how  nearly,  equal  intervals  on 
the  scale  of  numbers,  accord  with  equal  proportions  between  the  numbers  at  the  extremi- 
ties of  those  intervals  and  thus  the  degree  of  error  in  them,  and  the  part  where  it  exists 
to  the  greatest  extent  may  be  observed  : but  it  will  be  useless  to  do  so,  with  the  view  of 
finding  one  so  accurate  as  to  dispense  with  calculation  in  exact  analytical  experiments. 

Those  scales,  which  are  laid  down  directly  upon  wood,  though  not  liable  to  the  same 
sources  of  error  as  the  paper  scales,  are  still  seldom,  if  ever,  so  accurate  as  to  compete  with 
calculation. 

The  errors  just  referred  to,  relate  to  the  accuracy  of  the  scale  of  numbers,  and  its  pro- 
portional value  in  every  part.  Others  relate  to  the  imperfect  and  inaccurate  results  of  the 
experiments,  by  which  the  numbers  representing  the  equivalent  or  combining  quantities  of 
bodies  are  obtained.  If  an  inaccurate  result  be  mistaken  for  a correct  one,  and  the  pro- 
portional number  of  a body  be  entered  erroneously  upon  the  scale,  it  is  evident  that  all 
estimations  of  substances  including  that  body,  which  are  given  by  the  scale,  must  involve 
this  original  inaccuracy.  Whenever  therefore  a more  accurate  determination  of  the  num- 
ber of  a body  is  obtained  than  was  before  possessed,  its  place  on  the  scale  should  be  cor- 
rected; and  as  the  equivalent  numbers  of  substances,  previously  undetermined,  are  satis- 
factorily ascertained,  the  substances  themselves  should  be  put  upon  the  scale  in  their 
proper  situations,  as  before  described. 

In  consequence  of  the  unavoidable  errors  in  the  scale  of  numbers,  which,  however 
small,  still  interfere  in  the  investigation  of  complicated  cases,  and  the  determination  of 


516 


Appendix. 

accurate  conclusions,  the  instrument  should  only  be  used  in  those  instances  where  accu- 
racy within  a certain  degree  is  sufficient  for  the  purpose.  All  nicer  results  should  be 
obtained  by  calculation  from  a table  of  equivalents : if,  for  instance,  the  quantity  of  sul- 
phuric acid  in  64.7  grains  of  sulphate  of  baryta  were  required  to  two  or  three  places  of 
decimals,  it  would  be  better  to  take  the  equivalent  numbers  of  sulphate  of  baryta  and 
sulphuric  acid  from  such  a table,  and  to  say,  as  the  first  number  is  to  the  second,  so  is  64.7 
to  the  quantity  of  sulphuric  acid  it  contains,  than  to  work  with  the  scale.  The  present 
determination  of  the  sulphate  of  baryta  is  1 18,  and  that  of  sulphuric  acid  40,  hydrogen 
being  1 or  unity,  and  as  1 18  is  to  40,  so  is  64.7  to  21  932  very  nearly.  It  will  be  impossi- 
ble to  ascertain  this  last  number  accurately  on  an  ordinary  scale,  or  to  observe  how  far  it 
differs  from  22. 

There  are  numerous  tables  of  equivalents  published  in  different  chemical  works. 
Whichever  may  be  adopted  should  be  examined  from  time  to  time,  and  the  numbers  affix- 
ed to  bodies  on  it  corrected,  whenever  they  are  more  accurately  determined. 

It  has  been  shewn  by  Gay-Lussac  and  others  that  all  gases  and  all  volatile  substances 
when  in  the  state  of  vapour,  combine  or  act  chemically  in  volumes,  which  have  very  simple 
relations  to  each  other.  These  volumes  once  ascertained,  may  be  considered  in  the  rela- 
tion of  equivalents,  and  their  proportions  aie  so  simple,  as  to  be  remembered  without  the 
least  difficulty  : it  is  therefore  highly  advantageous  in  all  tables  of  chemical  equivalents,  to 
place  small  diagrams  by  the  sides  of  the  substances  and  their  numbers,  which  may  represent 
the  volumes  of  the  equivalents  when  brought  into  the  state  of  gas  or  vapour.  For  it  re- 
quires no  great  power  of  discernment  to  perceive  that,  if  bodies  combine  in  definite 
weights,  and  also  in  simple  ratios  of  volumes,  these  volumes  60  combining  must  contain 
the  weights  previously  found  to  be  definite  : for  whether  two  substances  which  combine 
to  form  a third,  are  observed  by  weight  or  volume,  still  they  combine  only  in  one  pro- 
portion. 

So  arranged,  the  table  will  have  an  appearance  of  the  following  kind  : 


Hydrogen 

1 

• □ 

Oxygen  ♦ 

8 

a 

Chlorine 

- 36 

. • □ 

Iodine 

- 125 

• □ 

Water  - 

9 

• □ 

Muriatic  acid  - 

- 37 

- CD 

Hydriodic  acid, 

- 126 

• m 

Ammonia 

- 17 

- m 

and  will  be  found  very  useful  when  referred  to  for  gaseous  or  vaporous  substances.  The 
proportions  of  these  volume?  are  much  more  easily  remembered  than  the  proportions  of 
their  equivalent  numbers  ; which,  added  to  the  facility  with  which  the  bulk  of  gases  or 
vapours  are  ascertained,  may  often  properly  induce  the  chemist  to  dispense  with  the  deter- 
mination of  weights,  and  work  with  volumes  only.* 


* Faraday’s  Chemical  Manipulation. 


Appendix, 


517 


TABLE  I. 

The  following  are  the  results  obtained  by  a commission  appointed  by  the 
Parisian  Academy  of  Sciences  to  examine  the  elastic  force  of  vapour They  were 
obtained  by  experiment  up  to  a pressure  of  25  atmospheres,  and  at  higher  pressures 
by  calculation . 


Elasticity  of  the  vap. 
taking  amospheric  £ 
press,  as  unity. 

Temperature  accord- 
ing to  Fahr. 

Elasticity  of  the  vap. 
taking  atmospheric 
press,  as  unity. 

Temperature  accord- 
ing to  Fahr. 

] 

212° 

13 

380.66° 

H 

233.96 

14 

386.94 

2 

250.52 

15 

392.86 

2 h 

263.84 

16 

398.48 

3 

275.18 

17 

403.82 

3 ft 

285.08 

18 

408.92 

4 

203  72 

19 

413.78 

4 ft 

-300.28 

20 

418.46 

5 

3U7.5 

21 

422.96 

5* 

314  24 

22 

427.28 

6 

320  36 

23 

431.42 

64 

326.26 

24 

435.56 

7 

331.70 

25 

439.34 

336.86 

30 

457.16 

8 

341.78 

35 

472.73 

9 

350.78 

40 

486.59 

10 

358.88 

45 

491.14 

11 

366.85 

50 

510.60 

12 

374.00 

* Braude’s  Jour.  N.  S.  viii ; 191. 


518 


Appendix. 


TABLE  II. 

Table  of  the  Elastic  Force  of  Aqueous  Vapour  at  different  Temperatures , 
expressed  in  Inches  of  Mercury. 


TEMP. 

Fah. 

Force  of  Vapour. 

TEMP. 

Fah. 

Force  of  Vapour. 

TEMP. 

Fah. 

Force  of  Vapour. 

Dalton. 

Ure. 

Dalton. 

Ure 

Dalton. 

Ure. 

3*2  c 

0.200 

0.200 

79° 

0.971 

126° 

3.89 

33 

0.207 

80 

1.00 

1.010 

127 

4.00 

34 

0.214 

81 

1.04 

128 

4.11 

35 

0.221 

82 

1.07 

129 

4.22 

36 

0.229 

83 

1.10 

130 

4.34 

4.366 

37 

0.237 

84 

1.14 

131 

4.47 

38 

0.245 

85 

1.17 

1.170 

132 

4.60 

39 

0.254 

86 

1.21 

133 

4.73 

40 

0.2t>3 

0.250 

87 

1.24 

134 

4.86 

41 

0.273 

88 

1.28 

1&5 

5.00 

5.070 

42 

0.283 

89 

1.32 

136 

5.14 

43 

0.294 

90 

1.36 

1.360 

137 

5.29 

44 

0.305 

91 

1.40 

138 

5.44 

45 

0.316 

92 

1.44 

139 

5.59 

46 

0.328 

93 

1.48 

140 

5.74 

5.770 

47 

0.339  ; 

94 

1.53 

141 

5.90 

48 

0.351 

95 

1.58 

1.640 

142 

6.05 

49 

0.363  | 

96 

1.63 

143 

6.21 

50 

0.375  . 

0.360 

97 

1.68 

144 

6.37 

51 

0.388  ; 

98 

1.74 

145 

6.53 

6.600 

52 

0.401  i 

99 

1.80 

146 

6.70 

53 

0.415  : 

100 

1.86 

1.860 

147 

6.87 

54 

0.429  I 

101 

1.92 

148 

7.05 

55 

0.443 

0.416 

102 

1.98 

149 

7.23 

56 

0.458  ! 

103 

2.04 

150 

7.42 

7.530 

57 

0.474 

104 

2.11 

151 

7.61 

58 

0.4!  H) 

105 

2.18 

2.100 

1 53 

7.81 

59 

0.507 

106 

2.25 

153 

8.01 

60 

0.524 

0.516 

107 

2.32 

154 

8.20 

61 

0.542 

108 

2.39 

155 

8.40 

8.500 

62 

0.5<  JO 

109 

2.46 

156 

8.60 

63 

0.578 

110 

2.53 

2.456 

157 

8.81 

64 

0.5H7 

111 

2.60 

158 

9.02 

65 

0.616 

0.630 

112 

2.68 

159 

9.24 

66 

0.(535 

113 

2.76 

160 

9.46 

9.600 

67 

0.655 

114 

2.84 

161 

9.68 

68 

0.676 

115 

2.92 

2.820 

162 

9.91 

69 

0.698 

116 

3.00 

163 

10.15 

70 

0.721 

0.726 

117 

3.08 

164 

10.41 

71 

0.745 

118 

aie 

165 

10.68 

10.800 

72 

0.770 

119 

3.25 

166 

10.96 

73 

0.796 

120 

3.&3 

2.300 

1.17 

11.25 

74 

0.823 

121 

3.42 

168 

11.54 

75 

0.851 

0.860 

122 

3.50 

169 

11.83 

76 

0.880 

123 

3.59 

170 

12.13 

12.050 

77 

0.910 

124 

3.69 

171 

12.43 

78 

0.940 

125 

3.79 

3.830 

172 

12.73 

Appendix. 


519 


TABLE  II. — Continued. 


TEMP. 

Fah. 

Force  of  Vapour.  1 

TEMP. 

Fah. 

Force  of  Vapour,  j 

I 

TEMP. 

Fail. 

Foree  of  Vapour. 

Dalton. 

Fre. 

Dal  ion. 

Ure. 

Dalton. 

lire. 

173° 

13.02 

224° 

37.53  j 

i 

275° 

83.13 

93.480 

174 

13.32 

225 

38.20 

39.1101 

276  1 

84.35 

175 

13.62 

13.550 

226 

38.89 

40.100 

277 

85.47 

97.800 

176 

13.92 

227 

39.59 

! 278  | 

86.50  | 

177 

14.22 

228 

40.30  1 

I 279  ! 

87.63  j 

101.600 

178 

14.52 

229  i 

41.02  | 

280 

88.75 

101.900 

179 

14.83 

230  ! 

41.75  i 

43.100 

281 

89.87  | 

104.400 

180 

15.15 

15.160 

231 

42.49  | 

j 282  t 

90.99 

181 

15.50 

232 

43.24  | 

283 

92.11 

107.700 

182 

15.86 

2&3 

44.00  j 

| 284 

93.23 

183 

16.23 

234 

44.78  | 

46.800i 

j 285 

94.35  S 

112.200 

184 

16.61 

235  | 

45.58  ! 

47.220 

1 286 

95.48 

1 

185 

17.00 

16.900 

236 

46.39 

i 

J 287 

96.64 

114.800 

186 

17.40 

237 

47.20  1 

! 

288 

97.80  1 

1 

187 

17.80 

238 

48.02  1 

50.3001 

289  | 

98.96 

118.200 

188 

18.20 

239  | 

48.84 

1 290 

100.12  1 

120.150  j 

189 

18.60 

240 

49.67  | 

51.700i 

! 291  ; 

101.28  j 

190 

19.00 

19.000 

241 

50.50  | 

! 

j 292 

102.45 

123.100 

191 

19.42 

242 

51.34 

53.600 

293 

103.63 

i 

192 

19.86  j 

243 

52.18  I 

294 

j 104.80 

i 126.700  | 

193 

20.32 

244 

53.03 

1 295 

105.97 

I 129.000 

194 

20.77 

245  j 

53.88 

| 56.340 

! 296 

107.14 

195 

2]  .22 

21.100 

246 

54.68 

1 

! 297 

108.31 

j 133.900 

196 

21.68  ; 

247 

55.54 

1 298 

109.48 

: 137.400  | 

197 

22.13 

248 

i 56.42 

' 60.400 

299 

i 110.64 

198 

22.69 

249 

! 57.31 

300 

| 111.81 

| 139.700 

199 

23.16 

250 

58.21 

! 61.900 

301 

112.98 

200 

23.64 

23.600 

251 

59.12 

; 63.500 

[ 302 

' 114.15 

144.300 

201 

! 24.12 

252 

60.05 

i 303 

* 115,32 

! 147.700  i 

202 

24.61 

253 

61.00 

304 

| 116.50 

203 

25.10 

254 

61.92 

66.700 

305 

117.68 

1 150.560  ; 

204 

25.61 

255 

62.85 

1 67.25  ! 

1 306 

118.86 

; 154.400  I 

205 

26.13 

25.900 

256 

63.76 

307 

120.03 

206 

26.66 

257 

64.82 

69.800 

308 

i 121.20 

| 157.700 

207 

27.20 

258 

65.78 

! 309 

I 122.37 

208 

27.74 

259 

i 66.75 

310 

1 123.53 

161.300 

209 

28.29 

260 

i 67.73 

72.300 

! 311 

124.69 

164.800 

210 

28.84 

28.880 

261 

i 68.72 

| 312 

' 125.85 

| 167.000 

211 

29.41 

262 

| 69.72 

75.900 

313 

| 127.00 

212 

30.00 

| 30.000 

263 

1 70.73 

314 

128.15 

1 

213 

30.60 

264 

! 71.74 

; 77.900 

i 315 

! 129.29 

* 

214 

31.21 

265 

| 72.76 

78.040 

! 316 

1 130.43 

215 

31.83 

266 

| 73.77 

317 

1 131.57 

216 

32.46 

33.400 

267 

! 74.79 

j 81.900 

318 

| 132.72 

217 

33.09 

j 268 

1 75.80 

319 

1 133.86 

218 

33.72 

269 

j 76.82 

84.900 

320 

; 135.00 

219 

34.35 

1 270 

i 77.85 

- 86.300 

321 

I 136.14 

220 

34.99 

1 35.540 

, 271 

i 78.89 

88.000 

322 

137.28 

221 

35.63 

36.700 

II  272 

79.94 

1 323 

138.42 

222 

36.25 

! 

||  273 

! 80.98 

91.200 

| 324 

: 139.56 

I 223 

36.88 

il  274 

1 82.01 

! 325 

140.70 

520 


Appendix. 


TABLE  III. 


Dr  Ure's  Table,  showing  the  Elastic  Force  of  the  Vapours  of  Alcohol  and 
Ettver  at  different  Temperatures , expressed  in  Inches  of  Mercury. 


Ether. 

Alcohol  sp 

. gr.  0 813. 

Alcohol  sp 

. gr.  0.813. 

Temp. 

Force  of  Vapour. 

Temp. 

Force  o:  Vapour. 

Temp. 

Force  of  Vapour. 

34° 

6.20 

32° 

0.40 

193.3 

46.60 

44 

8.10 

40 

0.56 

196.3 

50.10 

54 

10.30 

45 

0.70 

200 

53.00 

(34 

10.00 

50 

0.86 

206 

60.10 

74 

16.10 

55 

1.00 

210 

65.00 

84 

20.00 

60 

1.23 

214 

69.30 

94 

24.70 

65 

1.49 

216 

72.20 

104 

30.00 

70 

1.76 

220 

78.50 

105 

30.00 

75 

2.10 

225 

87.50 

110 

32.54 

80 

2.45 

230 

94.10 

115 

35.90 

85 

2.93 

232 

97.10 

120 

39.47 

90 

3.40 

2-36 

103.60 

125 

43.24 

95 

3.90 

238 

106.90 

130 

47.14 

100 

4.50 

240 

111.24 

135 

51.90 

105 

5.20 

244 

118.20 

140 

56.JX) 

no 

6.00 

247 

122.10 

145 

62.10 

115 

7.10 

248 

126.10 

150 

67.60 

120 

8.10 

249.7 

131.40 

155 

73.60 

125 

9.25 

250 

132.30 

160 

80.30 

130 

10.60 

252 

138.60 

165 

86.40 

135 

12.15 

254.3 

143.70 

170 

92.80 

140 

13.90 

258.6 

151.60 

175 

99.10 

145 

15.95 

260 

155.20 

180 

108.30 

150 

18.00 

262 

161.40 

185 

116.10 

155 

20.30 

264 

166.10 

190 

124.80 

160 

22.60 

195 

13-3.70 

165 

25.40 

200 

142.80 

170 

28.30 

205 

151.30 

173 

30.00 

210 

166.00 

178.3 

33.50 

180 

34.73 

182.3 

36.40 

185.3 

39.<K) 

190 

43.20 

Appendix. 


521 


TABLE  IV. 


Dr  Ore’s  Table  of  the  Quantity  of  Oil  of  Vitriol , of  sp.  gr.  1.8485,  and 
of  Anhydrous  Acid , in  100  Parts  of  dilute  Sulphuric  Acid , at  different  Densities. 


Liquid. 

Sp.  Gr. 

Dry. 

Liquid. 

Sp.  Gr. 

Dry. 

Liquid. 

Sp.  Gr. 

Dry. 

100 

1.8485 

81.54 

66 

1.5503 

53.82 

32 

1.2334 

26.09 

99 

1.8475 

80.72 

65 

1.5390 

53.00 

31 

L2260 

25.28 

98 

1.8460 

79.90 

64 

1.5280 

52.18 

30 

1.2184 

24.46 

97 

1.8439 

79.09 

63 

1.5170 

51.37 

29 

1.2108 

23.65 

96 

1.8410 

78.28 

62 

1.5066 

50.55 

28 

1.2032 

22.83 

95 

1.8376 

77.46 

61 

1.4960 

49.74 

27 

1.1956 

22.01 

94 

1.8336 

76.65 

60 

1.4860 

48.92 

26 

1.1876 

21.20 

93 

1.8290 

75.83 

59 

1.4760 

48.11 

25 

1.1792 

20.38 

92 

1.8233 

75.02 

58 

1.4660 

47.29 

24 

1.1706 

19.57 

91 

1.8179 

74.20 

57 

1.4560 

46.48 

23 

1.1626 

18.75 

90 

1.8115 

73.39 

56 

1.4460 

45.66 

22 

1.1549 

17.94 

89 

1.8043 

72.57 

55 

1.4360 

44.85 

21 

1.1480 

17.12 

88 

1.7962 

71.75 

54 

1.4265 

44.03 

20 

1.1410 

16.31 

87 

1.7870 

70.94 

53 

1.4170 

43.22 

19 

1.1330 

15.49 

86 

1.7774 

70.12 

52 

1.4073 

42.40 

18 

1.1246 

14.68 

85 

1.7673 

69.31 

51 

1,3977 

41.58 

17 

1.1165 

13.86 

84 

1.7570 

68.49 

50 

1,3884 

40.77 

16 

1.1090 

13.05 

83 

1.7465 

67.68 

49 

1.3788 

39.95 

15 

1.1019 

12.23 

82 

1.7360 

66.86 

48 

1.3697 

39.14 

14 

1.0953 

11.41 

81 

1.7245 

66.05 

47 

1.3612 

38,32 

13 

1.0887 

10.60 

80 

1.7120 

65.23 

46 

1.3530 

37.51 

12 

1.0809 

9.78 

79 

1.6993 

64.42 

45 

1.3440 

36.69 

11 

1.0743 

8.97 

78 

1.6870 

63.60 

44 

1.3345 

35.88 

10 

1.0682 

8.15 

77 

1.6750 

62.78 

43 

1.3255 

35.06 

9 

1.0614 

7.34 

76 

1.6630 

61.97 

42 

1.3165 

34.25 

8 

1.0544 

6.52 

75 

1.6520 

61.15 

41 

1.3080 

33.43 

7 

1.0477 

5.71 

74 

1.6415 

60.34 

40 

1.2999 

32.61 

6 

1.0405 

4.89 

73 

1.6321 

59.52 

39 

1.2913 

31.80 

5 

1.0336 

4.08  ' 

72 

1.6204 

58.71 

38 

1.2826 

30.98 

4 

1.0268 

3.26 

71 

1.6090 

57.89 

37 

1.2740 

30.17 

3 

1.0206 

2.446 

I 70 

1.5975 

57.08 

36 

1.2654 

29.35 

2 

1.0140 

1.63 

1 69 

1.5868 

56.26 

35 

1.2572 

28.54 

1 

1.0074 

0.8154 

• 68 

1.5760 

55.45 

34 

1.2490 

27.72 

1 67 

1.5648 

54.63 

33 

1.2409 

26.91 

66 


522 


Appendix. 


TABLE  V. 


Table  of  Muriatic  ( Hydrochloric ) Acid , hy  Dr  Ure. 


Acid  of 
120  in  1<)0. 

Specific 

Gravity 

Chlorine. 

Muriatic 

Cjab. 

Acid  of 
1^0  ill  loo. 

100 

1.2000 

39.675 

40.777 

66 

99 

1.1982 

39.278 

40.369 

65 

98 

1.1964 

38.882 

39.961 

64 

97 

1.1946 

38.485 

39.554 

63 

96 

1.1928 

38.089 

39.146 

62 

95 

1.1910 

37.692 

38.738 

! 61 

94 

1.1893 

37.296,38.330 

60 

93 

1.1875 

36.900 

37.923 

1 59 

92 

1.1857 

36.503 

37.516) 

1 58 

91 

1.1846 

36.107 

37.108, 

57 

90 

1.1822 

35.707 

36.700 

56 

89 

1.180235.310 

36.292 

55  ! 

88 

1.1782(34.913 

35.884 

54  ! 

87 

1.176234.517 

35.476 

53 

86 

1.174134.121 

35.068 

52  ! 

85 

1,1721:33.724 

34.660 

51  | 

84 

1.1701  • T3.328 

34.252 

50 

83 

1.1681 32.931 

33.845 

49 

82 

1.166132.535 

33.437) 

48 

81 

1.164132.136 

33.029 

47  1 

80 

1.162031.746 

32.621 

46  | 

79 

1.159931.343 

32.213 

45 

78 

1.157830.946 

31.805 

44 

77 

1.155730.550 

31.398 

43  1 

76 

1.153630.153 

30.990, 

42 

75 

1.1515  29.757 

30.582 

41  ! 

74 

1.149429.361 

30.174 

. 40  | 

73 

1.147328.964 

29.767 

39  | 

72 

1.145228.567 

29.359! 

1 38  | 

71 

1.1431 

28.171 

28.95] 

1 37 

70 

1.141027.772 

28.544  36 

69 

1.138927.376  28.136  35 

68 

1.136926.979 

1 27.728 1 34 

67 

1.1349(26.583 

1 27.321 1|  33 

Specific 

Gravuy. 


Muriatic 

Lius. 


1328  26.186  26.913 
1308)25.78920.505 
1287  25.392p26.098 


I 

I .  1 267 J24.996i25.690 

I I. 1247,24.599125.282 
1.122624.20224.874 
1.120623,80524.466 
1.1J8523.408J24.058 
1.1164  23.012l23.050 
1.114322.61523.242 

I. 112322.21822.834 

I I. 1 102  2 1 .822  22. 426 
j 1.1082  21.425*22.019, 
11.1061  21.02821.611 

I. 104120.6:1221.203 

II. 102020.23520.796 
1.1000  19.837  20.388 
1.0980  19.440  19.980 

I. 096019.04419.572 

II. 0939  18.647  19.165 
1.091918.25018.757 


.0899  17.854 
.0879  17.45? 
.085917.060 
,0838 16.664 
,0818 16.267 
.0798  15.870 


18.349 

17.941 

17.534 

17.126 

16.718 

16.310 


0758  15.077  15.494 
0738  14.680  15.087 
0718  14.284  14.679 
0697  13.887  14.271 
0677  13.490 13.863 
0657  13.094  13.456 


Ac|d  i f 
120  in  1U0. 

Specific 
G,  ayity. 

Chlorine. 

Muriatic, 

Gas. 

32 

1.0637 

12.697 

13.049 

31 

1.0617 

12.300 

12.641 

30 

1.0597 

11.903 

12.233 

29 

1.0577 

11.506 

11.825 

28 

1.0557 

11.109 

11.418 

27 

1.0537 

10.712 

11.010 

26 

1.0517 

10.316 

10.602 

25 

1.0497 

9.919 

10.194 

! 24 

1.0477 

9.522 

9.786 

23 

1.0457 

9.126 

9.379 

22 

1.0437 

8.729 

8.971 

21 

1.0417 

8.332 

8.563 

20 

1.0397 

7.935 

8.155 

19 

1.0377 

7.538 

7.747 

18 

1.0357 

7.141 

7.340 

17 

1.0337 

6.745 

6.932 

16 

1.0318 

6.348 

6.524 

15 

1.0298 

5.951 

6.116 

14 

1.0279 

5.554 

5.709 

13 

1.0259 

5.158 

5.301 

12 

1.0239 

4.762 

4.893 

11 

1.0220 

4.365 

4.486 

10 

1.0200 

3.968 

4.078 

9 

1.0180 

3.571 

3.670 

8 

1.0160 

3.174 

3.262 

7 1 

1.0140 

2.778 

2.854 

6 1 

1.0120 

2.381 

2.447 

5 

1.0100 

1.984 

2.039 

4 

1.0080 

1.588 

1.631 

3 

1.0060 

1.191 

1.224 

9 

1.0040 

0.795 

0.816 

1 ; 

1.0020 

0.397 

0.408 

* Dictionary  of  Arts  and  Manufactures,  873. 


Appendix. 


523 


TABLE  VI. 


Dr  Ure's  Table  of  the  Quantity  of  Real  or  Anhydrous  Nitric  Acid  in  100 
Parts  of  liquid  Acid , at  different  Densities . 


Sp  Gr. 

Real  Acid  in  100 
parts  of  the  li- 
quid. 

Sp.  Gr. 

Real  Acid  in  100 
parts  of  the  li- 
quid. 

Sp  Gr. 

Real  Acid  in  100 
parts  of  the  li- 
quid. 

1.5000 

79.700 

1.3783 

52.602 

1.1895 

26.301 

1.4980 

78.903 

1.3732 

51.805 

1.1833 

25.504 

1.4960 

78.106 

1.3681 

51.068 

1.1770 

24.707 

1.4940 

77.309 

1.3630 

50.211 

1.1709 

23.910 

1.4910 

76.512 

1.3579 

49.414 

1.1648 

23.113 

1.4880 

75.715 

1.3529 

48.617 

1.1587 

22.316 

1.4850 

74.918 

1.3477 

47.820 

1.1526 

21.519 

1.4820 

74.]  21 

1.3427 

47.023 

1.1465 

20.722 

1.4790 

73.324 

1.3376 

46.226 

1.1403 

19.925 

1.4760 

72.527 

1.3323 

45.429 

1.1345 

19.128 

1.4730 

71.730 

1.3270 

44.632 

1.1286 

18.331 

1.4700 

70.933 

1.3216 

43.835 

1.1227 

17.534 

1.4670 

70.136 

1.3163 

43.038 

1.1168 

16.737 

1.4640 

69.339 

1.3110 

42.241 

1.1109 

15.940 

1.4600 

68.542 

1.3056 

41.444 

1.1051 

15.143 

1.4570 

67.745 

1.3001 

40.647 

1.0993 

14.346 

1.4530 

66.948 

1.2947 

39.850 

1.0935 

13.549 

1.4500 

66.155 

1.2887 

39.053 

1.0878 

12.752 

1.4460 

65.354 

1.2826 

38.256 

1.0821 

11.955 

1.4424 

64.557 

1.2765 

37.459 

1.0764 

11.158 

1.4385 

63.760 

1.2705 

36.662 

1.0708 

10.361 

1.4346 

62.963 

1.2644 

35.865 

1.0651 

9.564 

1.4306 

62.166 

1.2583 

35.068 

1.0595 

8.767 

1.4269 

61.369 

1.2523 

34.271 

1.0540 

7.970 

1.4228 

60.572 

1.2462 

33.474 

1.0485 

7.173 

1.4189 

59.775 

1.2402 

32.677 

1.0430 

6.376 

1.4147 

58.978 

1.2341 

31.880 

1.0375 

5.579 

1.4107 

58.181 

1.2277 

31.083 

1.0320 

4.782 

1.4065 

57.384 

1.2212 

30.286 

1.0267 

3.985 

1.4023 

56.587 

1.2148 

29.489 

1.0212 

3,188 

1.3978 

55.790 

1.2084 

28.692 

1.0159 

2.391 

1.3945 

54.993 

1.2019 

27.895 

1.0106 

1.594 

1.3882 

1.3833 

54.196 

53.399 

1.1958 

27.098 

1.0053 

0.797 

^24  Apptndiz. 


TABLE  VII. 

I able  of  Lowitz , showing  the  Quantity  of  Absolute  Alcohol  in  Spirits  of 
different  Specific  Gravities. 


100 

Parts 

Specific  Gravity. 

100 

Parts. 

Specific 

Gravity. 

100  Parts. 

Sp.  Gravity. 

Alcohol. 

Water 

At  68°. 

At  60'. 

Alcohol 

Water 

At  64°. 

At 

Alcuhol. 

Water 

At  63°. 

At  60°. 

100 

0 

0.791 

0796 

66 

34 

0.877 

0.881 

32 

68 

0.952 

0.955 

99 

1 

0.794 

0.798 

65 

35 

0.880 

0.883 

31 

69 

0.954 

0.957 

98 

2 

0.797 

0801 

64 

36 

0.882 

0.886 

30 

70 

0.956 

0.958 

97 

3 

0.800 

0.804 

63 

37 

0.885 

0.889 

29 

71 

0.957 

0.960 

96 

4 

0.803 

0.807 

62 

38 

0.887 

0.891 

28 

72 

0.959 

0.962 

95 

5 

0.805 

0 809 

61 

39 

0.889 

0.893 

27 

73 

0.961 

0.963 

94 

6 

0.808 

0812 

60 

40 

0.892 

0.896 

26 

74 

0.963 

0.9G5 

93 

7 

0.811 

0815 

59 

41 

0.894 

0.898 

25 

75 

0.965 

0.967 

92 

8 

0.313 

0817 

58 

42 

0.896 

0.900 

24 

76 

0.966 

0.  ♦ 8 

91 

9 

0.816 

0820 

57 

43 

0.899 

0.902 

23 

77 

0.968 

0.970 

90 

10 

0.818 

0822 

56 

44 

0 901 

0.904 

22 

78 

0.970 

0.972 

89 

11 

0.821 

0.825 

55 

45 

0.903 

0 906 

21 

79 

0.971 

0973 

88 

12 

0.823 

0-827 

54 

46 

0.905 

0.908 

20 

80 

0.973 

0.974 

87 

13 

0 826 

i 0-830 

53 

47 

0.907 

0.910 

19 

81 

0.974 

0.975 

86 

14 

0.828 

! 0-832 

52 

48 

0.909 

0.912 

18 

82 

0.976 

0.977 

85 

15 

0.831 

0-835 

51 

49 

0.912 

0.915 

17 

83 

0.977 

0.978 

84 

16 

0 834 

0-838 

50 

50 

0.914 

0.917  i 

16 

84 

0.978 

0.979 

83 

17 

0.836 

0840 

49 

51 

0.917 

0.920 

15 

85 

0.980 

0.981 

82 

18 

0.839 

0.843  ! 

48 

52 

0.919 

0.922 

14 

86 

0.981 

0.982 

81 

19 

0.842 

0.846  , 

47 

53 

0.921 

0.924 

13 

87 

0.983 

0.984 

80 

20 

0.844 

0.848  ; 

46 

54 

0.923 

0.926 

12 

88 

0.985 

0.986 

79 

21 

0.847 

0.851 

45 

55 

0.925 

0.928 

11 

89 

0.996 

0.987 

78 

22 

0.849 

0.853  i 

44 

56 

0.927 

0.930 

10 

90 

0.987 

0.988 

77 

23 

0.851  ! 

0.855 

43 

57 

0.930 

0.933 

9 

91 

0.988 

0.989 

76 

24 

0 853 

0.857 

42 

58 

0.932 

0.935 

8 

92 

0.979 

0.990 

75 

25 

0.856  I 

0.860 

41 

59 

0.934 

0.937 

7 I 

93 

0.991 

0.991 

74 

26 

0.859 

0.863 

40 

60 

0.936 

0.939 

6 ! 

94 

0.992 

0.992 

73 

27 

0.861 

0.865 

39 

61 

0.938 

0.941 

5 | 

95 

0.994 

72 

28 

0.863 

0 867 

39 

62 

0.940 

0.943 

4 

96 

0.995 

71 

29 

0.866 

0.870  ' 

37 

63 

0.942 

0.945 

3 ' 

97 

0.997 

70 

30 

0.868  1 

0.872 

36 

64 

0.944 

0.947 

o ' 

98 

0.998 

69 

31 

0.870  1 

0.874  ! 

35 

65 

0.946 

0.949 

1 

99 

0.999 

68 

32 

0.872 

0.875  ) 

34 

66 

0.948 

0.951 

0 

100 

1.000 

67 

33 

0.875 

0.879  1 

S3 

67 

0.950 

0.953 

| 

Appendix. 


Specific  Gravity  of  E 

ssential  and  other  Oils. 

Oil  of  Anise-seed, 

0.9958 

“ “ Bergamot,  . 

0.685 

*4  “ Cajeput, 

0.048 

“ “ Caraway,  .... 

. 0.975 

“ M Cassia,  .... 

1.071 

“ u Cinnamon, 

1.035 

“ 44  Cloves,  .... 

1.061 

44  “ Fennel,  .... 

. 0.997 

Oil  of  Juniper,  ... 

0.911 

44  44  Lavender,  . . 

. 0.898 

44  “ Lemons, 

0.8517 

44  44  Nutmegs,  . 

. 0.948 

44  “ Peppermint, 

0.899 

44  “ of  Roses,  (Ottar  of  Roses) 

. 0.832 

44  44  Rosemary, 

0.85 

Oils  of  Fermented  Liquors. 


Oil  of  Grain  Spirits,  .... 

. . . . 0.635 

44  44  Potato  Spirits,  .... 

. 0.821 

Tables  of  Weights  and  Measures , of  the  Correspondence  between  Fahren- 
heit's, Reaumur's,  and  the  Centigrade  Thermometers,  and  of  Freezing  Mixtures. 


WEIGHTS  AND  MEASURES. 

WEIGHTS. 

The  standard  according  to  which  the  present  system  of  weights  is  regulated,  is  the  Troy 
brass  pound.*  It  contains  5760  grains. 


Imperial  Standard  Troy  Weight 


24 

grains  = 

1 pennyweight. 

20 

pennyweights  = 

1 ounce. 

12 

ounces  = 

or,  n 

1 pound. 

Grains. 

Pennyweights. 

Ounces. 

Pound . 

24 

= 1 = 

l 

21X 

itItt 

480 

= 20  — 

1 

tV 

5760 

= 240  = 

12 

* For  important  remarks  on  weights  and  measures  and  on  the  standard  weights  of  the  United 
States,  see  HassieFs  Reports  to  Congress,  \ $37— $. 


526  Appendix. 

Avoirdupois  Weight. 

The  pound  avoirdupois  contains  7000  grains,  each  of  which  is  equal  to  a Troy  grain, 
being  thus  heavier  than  the  Troy  pound  by  1240  grains. 


1 drachm 

— 

27.34375  grains. 

16  drachms 

= 1 ounce 

— 

437.5 

16  ounces 

= 1 pound 

— 

7000 

28  pounds 

= 1 quarter 

= 

J 96000 

4 quarters 

= 1 cwt.  or 

112  lbs. 

= 

784000 

20  cvvts. 

= 1 ton 

or, 

= 

15680000 

Pound. 

Ounces. 

Drachms. 

1 = 

16  = 

256 

= 7000  grains. 

Tff  = 

I = 

16 

= 437.5 

i 

TF  = 

1 

= 27.34375 

Apothecaries ’ Weight. 

The  pound  in  Apothecaries'  Weight  is  equal  to  the  Troy  pound,  containing 5760  grains, 
but  is  differently  subdivided. 

1 pound  ||j  = 12  ounces  = 5760  grains. 


1 ounce  3 

— 

S diachms 

— 

480 

1 drachm  3 

— 

3 scruples 

60 

1 scruple  3 

= 

20  grains 

= 

20 

or. 

Pound.  Ounces. 

Drachms.  Scruples. 

Grains. 

1 = 12 

— 

96  = 

288  = 

5760 

1 

= 

8 = 

24  = 

480 

1 = 

3 = 

60 

1 = 

20 

The  following  tables  show  the  correspondence  between  the  Troy , Avoirdupois,  an  d 
Apothecaries’  Weights. 


Troy  Weight. 


Avoirdupois. 


Apothecaries’ 


9 1 pound 

1 ounce 
1 pennyweight 


13  oz.  2 dr.  17.8125  grs. 
1 1 15  1562 

0 0 24. 


1 pound. 

1 ounce. 

1 scruple  4 grs. 


Avoirdupois. 


Troy  Weight. 


Apothecaries’. 


1 pound  = 1 Jb  2 oz.  11  dwt.  10  gr.  = 1 lb  2 § 4 3 2 9 

1 ounce  = 0 0 18  5.5  = 0 0 7 0 17.5  grs. 

1 drachm  = 0 0 1 3.34  = 0 0 0 1 7.34 


Apothecaries’. 

1 pound 
1 ounce 
1 drachm 
1 scruple 


Troy  Weight. 

1 pound 

1 ounce 

2 dwt.  12  gr. 

0 20 


Avoirdupois. 


= 13  oz.  2 dr.  17.8125  grains. 

= 1 1 15.1562 

= 0 2 5.3 125 

= 0 0 20. 


French  Decimal  If  eight. — Gramme  = 15.4063  Troy  Grains. 


Milligramme 

Centigramme 

Decigramme 

Gramme 


0.0154  grain? 
0.1.540 
1.5406 
15.4063 


Appendix* 


527 


MEASURES. 

The  Imperial  Standard  Gallon  contains  ten  pounds  Avoirdupois  weight  of  distilled 
water,  weighed  in  air  at  62°  Fahr.  and  30°  Barotn.,  or  12  lb.  1 ounce  16  pennyweights  and 
16  grains  Troy,  = 70,000  grains  weight  of  distilled  water.  A cubic  inch  of  distilled 
water  weighs  252.458  grains,  and  the  imperial  gallon  contains  277  274  cubic  inches. 


Imperial  Measure. 


Quarter 

Bushel 

Peck 

Gallon 


1 Quart 


8 Bushels. 
4 Pecks. 

2 Gallons. 
4 Quarts. 
2 Pints. 


Distilled  Water. 


Grains.  Avoird.  lb. 

Cub.  hich. 

Pint. 

Quart.  Galls. 

Pecks. 

Bush. 

Qv. 

8750  = 1.25  = 

34 .659 

= 1 

17500  = 2.5  = 

69.318 

2 

= 1 

70000  = 10  = 

277.274 

= 8 

= 4=1 

140000  = 20  = 

554.548 

= 16 

= 8 = 2 

= 1 

560000  =80  = 

2218.192 

= 64 

= 32  = 8 

= 4 = 

1 

4480000  = 640  = 

17745.536 

= 512 

= 256  = 64 

= 32  = 

8 = 

1 

Apothecaries ’ Measure  (London  Pharmacopoeia). 

The  gallon  of  the  former  wine  measure,  and  of  the  present  Apothecaries’  measure,  con- 
tains 58333.31  grains  weight  of  distilled  water,  or  231  cubic  inches,  the  ratio  to  the  impe- 
rial gallon  being  nearly  as  5 to  6,  or  as  0 8331  to  1. 

1 Gallon  ~ 


1 Pint  0 
1 Ounce  f § 

1 Drachm  f 5 


8 Pints. 

16  Ounces. 

8 Drachms. 

60  Drops,  or  Minims. 


Gallon.  Pints. 

Ounces. 

Drachms. 

Minims. 

Gr.  of  Dist.  Water 

•.  Cub  Inch. 

1 ==  8 

= 128 

= 1024 

= 61440 

= 58333.31 

= 231 

1 

= 16 

= 128 

.==  7680 

= . 7291.66 

= 28.8 

1 

-=  8 

= 4S0 

— 455,72 

= 1.8 

1 

= 60 

= 56.96 

= 0.2 

French  Decimal  Measure  of  Capacity,  Litre  — 61.02525 
15406.312  grains  of  distilled  ivater. 


British  cubic  inches . or 


Millilitre 

Centilitre 

Decilitre 

Litre 


0.06102  cubic  inches. 
0.61025 
6.10252 
61.02525 


Table  showing  the  Weight  in  Grains  of  various  Measures  (Apothecaries)  of  liferent 

Fluids. 


'Specific 

Gravity. 

Weight  in  Grains  of 

1 fuit. 

1 Ounce. 

1 Drachm. 

| 1 Minim . 

Distilled  Water 

Sulphuric  Ether 

Alcohol - 

Solution  of  Ammonia  ... 

Muriatic  acid  - 

Nitric  acid 

Sulphuric  acid 

1.000 

0.720 

0.796 

0.925 

1.118 

1.480 

1.848 

7291  66 
524  >.99 
5801.16 
6744.78 
8152.07 
10791.65 
13474.98 

455.72 

328.12 

362.76 

421.54 

509.50 

674.47 

842.18 

56.96 
41.01 
45.34  ! 
52.69 
63  68 
84.30 
105.27 

0.947 
0 683 
0.749 
0.878 
1.061 
1405 
1.754 

628 


Appendix. 


Fig'-r. 


G=P 


%\ 


A-/ 


V 


Apparatus  for  obtaining  Potassium.  Fig.  1,  an  iron  pot  made  of  the 
best  malleable  iron,  about  12  inches  long,  and  5 or  6 in  diameter ; the 
iron  at  least  three  eighths  of  an  inch  thick.  A lid  is  fitted  accurately  to 
it,  and  this  is  secured  by  an  iron  rod  passing  through  two  holes  in  the 
upper  part  of  the  pot.  A gun-barrel  passes  from  the  cover  to  the  re- 
ceiver. The  receiver  consists  of  two  pieces.  It  is  made  of  tinned  cop- 
Fig.  2.  per.  The  piece  (Fig.  2)  is  a thin  parallelopiped,  10 

inches  long,  5 or  6 broad,  and  thick.  It  is  shut 
at  the  top  and  open  at  the  bottom.  It  is  divided  by 
l£)  a diaphragm,  a , to  within  one  third  of  the  bottom. 

On  one  side  is  a small  hole  into  which  the  end  of 
the  gun-barrel  enters,  and  to  which  it  is  luted  air-tight,  or,  what  is 
better,  fitted  by  grinding.  Opposite  to  it  is  another  opening,  fitted 
with  a cork  through  which  an  iron  wire  passes  air-tight.  It  passes 
also  through  a cork  fitted  into  the  hole  in  the  diaphragm.  The  use 
of  this  wire  is  to  keep  the  gun-barrel  from  being  filled  up  during  the 
process.  Fig.  3 is  the  other  part  of  the  receiver,  open  above,  and  shut 
below.  Fig.  2 fits  it  exactly.  A few  inches  of  naphtha  are  put  into 
Fig.  3,  and  Fig.  2 is  placed  in  it;  being  well  luted  with  fat  lute  or 
putty  to  exclude  air.  A bent  glass  tube  proceeds  from  2 at  6,  Fig.  4, 
well  luted,  which  plunges  into  a vessel  filled  with  naphtha;  to  allow 
the  escape  of  the  gases. 

Fig.  4 shows  the  arrange- 
ment of  the  iron  pot,  recei- 
ver, and  furnace.  The  iron 
pot  should  be  luted  before  it  is  used,  as  it  is  apt 
to  be  melted  ; this  is  best  done  by  binding  it 
round  with  iron  wire,  covering  it  with  a stiff 
cla}"  lute  mixed  with  about  one  fifteenth  part  of 
iron  filings  and  charcoal,  and  a little  thread  cut 
into  pieces  about  an  inch  in  length.  This  is 
bound  round  again  with  wire,  and  the  whole 
rubbed  over  with  lute.  It  should  be  allowed  to 
dry  a day  or  two  before  using,  and  the  cracks 
should  be  filled  up. 

The  iron  pot  is  placed,  as  represented,  above 
a piece  of  fire-brick,  and  fixed  to  it  with  fine 
clay.  The  body  of  the  furnace  may  be  about  18 
inches  long,  15  broad,  and  18  deep  ; the  walls 
from  5 to  10  inches  thick,  and  the  flue  6 inches 
square  (inside). 

The  upper  part  of  the  furnace  is  covered  by  a 
flat  cast-iron  plate  about  three  fourths  of  an  inch 
thick,  and  with  an  opening  in  the  centre 
through  which  fuel  is  introduced,  a moveable 
cover  of  th§  same  metal  being  fitted  to  it  by  an  iron  bolt  passing  through  a hole  bored  in  it 
and  in  the  plate  ; it  allows  us  also  to  see  very  conveniently  the  state  of  the  apparatus  within 
the  furnace  Another  opening  is  made  on  a level  with  the  branders,  to  allow  the  fire  to 
be  withdrawn  whenever  it  may  be  necessary  ; it  is  constructed  in  such  a manner  as  to  al- 
low it  to  be  easily  closed  up  with  a brick  and  a little  mortar,  which  may  be  removed  again 
with  the  same  facility.  A door  is  also  placed  below  to  regulate  the  admission  of  the  air, 
and  a damper  in  the  vent  to  diminish  the  draught  if  this  should  be  necessary.  The  aper 
ture  in  the  side  of  the  furnace  for  the  gun-barrel  must  not  be  forgotten. 

After  everything  has  been  properly  adjusted,  the  fire  may  be  put  on.  A little  water 
comes  away  when  the  apparatus  becomes  red-hot ; soon  after,  carbonic  oxide  gas  is 
evolved  ; and  when  it  is  at  white  heat,  a very  dense  vapour  is  disengaged,  which  burns 
with  a brilliant  flame.  The  receiver  intended  to  condense  the  potassium  may  then  be 
fixed  to  the  extremity  of  the  gun  barrel  without  the  furnace.  The  receiver  is  that  recom- 
mended by  Berzelius,  which  should  be  kept  cold  by  ice. 

When  the  gas  begins  to  be  disengaged  slowly,  this  arises  in  general  from  the  tube  being 
so  obstructed  as  to  prevent  it  from  passing  out  readily  ; the  plug  is  then  taken  out,  and  the 
obstructing  matter  removed  as  completely  as  possible,  but  if  the  gas  does  not  appear  then 
to  increase  in  quantity,  it  will  be  better  to  withdraw  the  fire  and  allow  the  apparatus  to 
cool.  Too  mueh  caution  cannot  be  taken  in  endeavouring  to  clear  the  tube  either  during 
the  distillation  or  after  the  apparatus  has  been  allowed  to  cool,  for  the  tube  being  frequently 
obstructed  while  the  materials  are  at  a high  temperature  and  still  producing  gas,  it  is  obvi- 


Appendix.  529 

ous  that  a large  quantity  must  be  accumulated  in  a short  time,  and  the  moment  the  impe- 
diment to  its  free  passage  is  removed,  it  often  expands  with  explosive  violence,  and  gives 
rise  occasionally  to  serious  accidents* 

The  mixture  of  charcoal  and  potassa  is  prepared  most  easily  by  exposing  six  or  seven 
pounds  of  cream  of  tartar  (cr  ude  tartar  may  be  used)  tq  a red  heat,  in  large  earthen  or  iron 
crucibles,  till  no  more  gas  is  disengaged,  reducing  it  to  powder  in  a mortar,  when  cold. 
This  is  transferred  immediately  to  an  iron  pot,  that  it  may  be  prevented  from  attracting 
water  from  the  air.  Brunner  states  that  when  the  tartar  is  mixed  with  one  twelfth  of  its 
weight  of  charcoal  a larger  quantity  of  potassium  is  obtained.  This  additional  quantity  of 
charcoal  is  useful  also  in  preventing  the  fusion  of  the  carbonate  of  potassa  at  the  high  tem- 
perature to  which  it  is  afterwards  exposed. 

A powerful  lamp  (Fig.  5),  where  a large  flame  is  required,  may  be 
formed  by  filling  a ring  of  tin  of  an  inch  or  more  in  diameter,  and  an 
inch  in  length,  with  wick  yarn,  and  placing  it  in  a shallow  tin  vessel, 
in  the  centre  of  which  is  a tube  or  cavity  into  which  the  ring  fils  loosely. 

The  tube  is  soldered  at  the  top  to  the  body  of  the  lamp,  but  a small 
space  is  left  at  the  bottom  to  permit  the  passage  of  the  alcohol  with 
which  the  lamp  is  filled.  The  lamp  is  filled  by  pouring  the  alcohol  upon 
the  wick.  The  upper  edge  of  the  ring  rises  a little  above  the  top  of  the 
lamp,  as  seen  in  the  section  Fig.  (i. 

The  power  of  different  metals  of  conducting  heat  may  be  shown 
Fi".  7.  by  the  apparatus,  Fig.  7.  See  paragraph  203. 


Fig.  8 represents  a convenient  funnel  for 
conveying  gases  into  vessels  the  funnel  be- 
ing prolonged  by  a tube  at  right  angles,  and 
inverted'  in  a basin  of  water,  a small  piece 
may  be  removed  from  the  edge  to  admit  the  pipe  from  a 
retort. 

Fig.  9.  Advantage  will  sometimes  be  gained  by  cement- 

ing a thin  piece  of  wood  to  a cork  made  tapering, 

through  both  which  tubes  may  be  passed  and  secured,  as  in  Fig.  9,  for  intro- 
ducing into  bottles  and  flasks. 


Barium , Strontium , and  Calcium . Dr  Hare  has  recently  obtained,  by  an  im- 
proved process,  all  three  of  these  metals.  Saturated  solutions  of  the  chlorides 
were  substituted  for  moistened  oxides,  and  exposed  to  a powerful  Voltaic  circuit,  in  con- 
tact with  mercury  as  a cathode  ; the  resulting  amalgams  were  distilled  by  means  of  vessels 
of  iron.  The  avidity  of  the  metals  for  oxygen  was  such,  that,  to  see  their  bright  metallic 
surfaces,  it  was  necessary  for  the  eye  to  follow  closely  the  movements  of  the  file  or  bur- 
nisher. They  were  brittle,  and  much  harder  than  potassium  or  sodium.  See  Jhncr.  Jour. 
Oct.,  1839. 


* On  one  occasion  when  the  apparatus  was  not  touched  till  36  hours  after  the  fire  had  been 
withdrawn,  on  tapping  the  gun -barrel  to  remove  it  more  easily,  the  whole  of  the  glass  tube  was 
broken  to  pieces  so  excessively  small  that  no  trace  of  it  could  be  found;  a peculiar  detonating 
compound  indeed  is  lormed  within  the  tube,  small  quantities  of  which  were  found  in  almost 
every  part  of  the  room,  and  exploded  with  very  little  friction,  Keid. 


530 


Appendix. 


Absorption  of  Gases  by  Charcoal. 

Saussure  found  that  charcoal  prepared  from  box-wood  absorbs  during  the  space  of  24 
36  hours,  of 

Ammoniacal  gas,  .....  90  times  its  vol. 

Hydrochloric  acid,  . . . . .85 

Sulphurous  ......  65 

Sulphuretted  hydrogen,  . . . . .81  (Henry.) 

Nitrous  Oxide,  .....  40 

Carbonic  acid  . . . . . .35 

Olefiant  gas,  ......  35 

Carbonic  oxide,  ......  9.42 

Oxygen,  . . . . . . 9.25 

Nitrogen,  .......  7.5 

Hydrogen,  . . . . . . 1.75 


GENERAL  INDEX 


ABB 

ABB  RE  VIA  TION  of  symbols , 35 
Acetates , 377 
Acetal,  447—452 
Acetate  of  alumina,  380 
ammonia,  378 
copper,  379 
iron,  378 
lead,  379 
lime,  378 
mercury,  379 
morphia,  439 
potassa,  378 
tin,  378 
zinc,  378 
Acetic  acid,  376 

procured,  376 
by  platinum,  377  (n*) 
from  wood,  376 
glacial,  377 
properties  of,  376 
theory  of  its  formation,  489 
Acetification,  489 
Acetone,  455  (n) 

Acetous  acid,  376 

fermentation,  489 

Acidity,  oxygen  not  essential  to,  122 
Acids,  containing  nitrogen,  391 

oxygen,  action  of,  122 

fixed,  382 

produced  by  chlorine,  122 

hydrogen,  122 

from  metals,  225 
termipology  of,  103 
metals  oxidized  by,  122 
oily,  390 

transfer  of,  by  galvanism,  97 
vegetable,  369 
Acid,  acetic,  376 — 489 
acetous,  376 
aldehydic,  447  (n) 


ACI 

Acid,  aloxanic,  426 

althionic,  394 — 454 
antimonic,  287 
antimonious,  286 
apocrenic,  394 
arsenic,  275 
arsenious.  272 
azuhnic,  391 
benzoic,  381 
boracic,  175 
bromic,  204 
carbonic,  153 

quantity  produced  by  respiration, 

498 

camphovinic,  454 
carbazotic,  392 
chloric,  192 
chloriodic,  201  (n) 

chlorocarbonic,  195  (n) 
chloronitrous,  195  (n) 
cholic,  501 
chromic,  279 
cinnamomic,  382  (n) 

citric,  383 
columbic,  285 
crenic,  394 
croconic,  373 
cyanic,  398 
cyanilic,  422 
cyanuric,  403 
erythric,  see  Alloxan , 425 
esculic,  3S2  (n) 

ethionic,  395 
fluoboric,  207 
fluosilicic,  208 
formo-benzpilic,  395 

composition  of,  396 

formic,  373 

fuluninic,  401 


* (n)  signifies  note. 


ALB 


ACI  532 


Acid,  gallic,  3S7 

hydro-bromic,  203 
hydriodio,  198 
hydro-chloric,  184 
hydro-cyanic,  405 

hydrous,  406 

hydro -ferrid  cyanic,  417 

hydro-ferrocyanic,  412 

hydro-fluoric,  205 
hydro-oleic,  391 
hydro-selenie,  217 
hydro-sulphuric,  214 
hydro-telluric,  293  (n) 
hypo-chlorous,  189 
hypo-nitrous,  145 
hydro-sulphocyanic,  420 
hypo-phosphorous,  172 
hypo-sulpho-indigotic,  395 — 457  (n) 
hypo-sulphuric,  168 

hypo-sulphurous,  168 

indigoticJ  392 

iodic,  200 

kinic,  388 

lactic,  380 — 503 

lithic,  504 

malic,  382 

margaric,  391 

meconic,  386 

mellitic,  375 

mesoxalic,  427 

metaphosphoric,  174 

molybdic,  282 

monoxylic 

muriatic,  184,  188 

mykomelinic,  427 

naphthalic,  381  (n)  480  (o) 

nitric,  147 

process  for,  148  (n) 

nitro-hydrochloric,  188 

nitro-sulpluiric,  329,  337  (n) 

nitrous,  146 

oleic,  391 

osmic,  319 

oxalic,  369 

oxalovinic,  454 

oxaluric,  428 

oxymuriatic,  see  Chlorine 

parabanic,  428 

pectic,  393 

perchloric,  193 

periodic,  201  (n) 

permanganic,  254 

phosphoric,  173 

glacial,  175 

phosphorous,  173 
phosphbvinic,  395  (n) — 454 
pinic,  464 
prussic,  405 
purpuric,  433 — 504 
pyrogailic,  387 
pyroligneous,  376 
pyrophosphoric,  174 
racemovinic,  454 
rhodizonic,  373 
selenic,  180 


Acid,  selenious,  180 
silicic,  177 
silici-fluoric,  208 
silico-hydrofluoric,  361 
sorbic,  see  Malic,  382 
stearic,  390, 391 
suberic,  381  (n) 

succinic,  375 — 466 
sulpho-cetic,  448 
sulpho  -oleic,  391 
sulpho-indigotic,  395 — 457  (n) 
sulpho-naphthalic,  395 
sulphur,  355 
sulphuric,  165 
sulphurous,  163 
silvic,  464 
tannic,  388 
tartaric,  383 
tartrovinic,  454 
telluric,  294  (n) 
tellurous,  293 
thionuric,  429 
titanic,  292 

transfer  of,  by  galvanism,  97 
tungstic,  283 
uramilic,  430 
uric,  423—504 
vanadic,  281 
Action,  chemical,  14 
Adipocere,  492 
Aeriform  bodies,  see  Gases 
conducting  power  of,  65 
expansion  of,  41 

matter,  its  power  of  sustaining  indue 
tion,  82 

Affinity,  chemical,  13 

results  of,  13 

of  aggregation,  2 
elective,  11 

inferred,  17 

single,  17 

tables  of,  18 

influenced,  19 
measured.  23 
Agitation,  its  effect,  17 
Air , effect  of  respiration  on,  498 
atmospheric,  136 
analysis  of,  138 
an  electrode,  99 
composition  of,  137,  139 

uniformity  of,  139 

compression  of  evolves  heat,  50 
Dalton’s  theory,  140 
Graham’s  experiments,  140 
necessary  to  fermentation,  488 
properties  of,  136 
pump,  137 

purity  estimated,  137 
thermometer,  46 
Alabaster,  325 

Albumen, antidote  to  corrosive  sublimate, 30 
animal,  492 
liquid,  493 
solid,  493 
vegetable,  474 


AMM 


533 


ANT 


Alchoates,  444 
Alcohol , 441 

absolute,  442 

Alcohol , action  of  platinum  on,  377  (n) 
composition  of,  445 
of  sulphur,  220 
strength  of  ascertained,  443 
uses,  443 

in  wine,  table  of,  445 
Aldehyde,  446 

its  composition,  447  (n) 

resin,  447 

Algaroth,  powder  of,  286 
Alkali,  volatile,  208 
Alkalies , 104,  22S 

metallic  bases  of,  229 
vegetable,  232—434 
Alkaligenous  metals,  228 
Alkaline  earths,  228 
Alkalimeter , 158 
Allanile,  289 
Allantoin,  425 
Alloys,  <2,21 

characters  of,  224 
formed,  224  (h) 

qualities  of  the  metals  altered  in,  228 
Alloxan,  425 
Alloxanic  acid,  426 
Alloxantin,  430 
Almonds,  485 

bitter,  oil  of,  468 
Althionic  acid,  394 — 454 
Alum,  330 

impurities  in,  247  (n) 
chrome,  331 
iron,  331 
magnanese,  331 
Alumina,  247 

acetate  of,  380 
in  blood,  496 
obtained,  247 
purified,  247  (n) 

properties  of,  247 

quantity  of  water  taken  up  by, 248  [n] 
recognized,  248 
sulphates  of,  326 
Aluminium,  247 

sesquichloride  of,  248 

process  for,  248 

sesquioxide  of,  247 
Alizarin,  458  (n) 

Amalgams,  307 
Amber,  466 

acid  of,  375 
Ambergris,  502 
Amides , theory  of,  364 

signification  of  the  term,  467 
Amidet,  364 
Amidin,  472 
Ammelid,  398 
Ammelin,  397 
Ammonia,  208 

preparation  of,  208 
acetate  of,  378 


Ammonia,  anomalous  cyanate  of,  399 
bicarbonate  of,  350 
action  of  chlorine  on,  210 
action  on  oxalic  ether,  467  (n) 
analysis  of,  210 
benzoate  of,  382 
basic  cyanate  of,  399 
carbonate  of,  349 
carbo-sulphuret  of,  357 
chlorides  with,  359 
cleaning  gold  by,  296  (n) 
cyanates  of,  399 
liydrochlorate  of,  353 

native,  354 

hydrocyanate  of,  409 
hydrofluate  of,  354 
bydrosulphate  of,  354 
inflamed  with  oxygen,  209 
metallization  of,  307 
muriate  of,  353 
nitrate  of,  335 
oxalate  of,  371 

phosphate  of,  and  magnesia,  344 
purpurate  of,  see  Murexid,  431 
sub-carbonate  of,  350 
sulphate  of,  323 
urate  of,  505 
water  of,  210 
Ammonia-aldehyde,  446 
Ammoniac  Sal,  353 
Ammoniacal  salts  recognized,  353 
Ammonia  and  magnesia,  phosphate  of,  344 
Ammonium,  209 

bicarbonate  of  oxide  of,  350 
cyanuret  of,  409 
ferrocyanuret  of,  413 
nitrate  of  oxide  of,  335 
sesquicarbonate  of  oxide  of,  350 
sulphate  of  oxide  of,  323 
Amygdalin,  475  (n) 

Amylaceous  substances,  471 
Amylin , 472 
Analysis,  defined,  36 
proximate,  37 
of  light,  74 
Anhydrite,  325 
Animal  carbon,  152 — 481 
heat,  498 

theories  of,  499 

substances,  490 

contain  nitrogen,  490 

— — proximate  principles  of, 490 

putrefaction  of,  491 

• effect  of  heat  upon, 491 

Animals,  effect  of  narcotina  upon,  437 

Annealing,  178 

Animal  heat,  494 

Anions,  defined,  98 

Anotta , 458 

Anode,  defined,  98 

Antimonial  powder,  286 

Antimonic  acid,  287 

Antimonio-sulphurets,  358 

Antimonious  acid,  286 


ATO 


534 


BER 


Antimony , 285 

alloys  of,  288 
butter  of,  287 
chlorides  of,  287 
detected,  286 

distinguished  from  arsenic,  275 
glass  of,  287 
golden  sulphuret  of,  288 
ignited,  detonates  with  vapour,  25 
salts  of,  286 
sulphurets  of,  287 
tartarized,  286 
Antiseptics,  491 
Ants,  acid  from,  373 

ApperCs  method  of  preserving  meat,&c.491 
Apocrenic  acid,  394 
Apparatus,  chemical,  106,  115 
for  freezing,  53  (n) 

Nooth’s,  154  (n) 

for  liquefying  carbonic  acid,  see  In- 
dex to  apparatus 
Aqua  Ammonia,  210 
fort  is,  151 
regia,  188,  354 
Arabin,  473 
Arbor  Diana,  310 
Saturni,  299 
Argot,  384 
Arrow-root,  472 
Arseniatec,  345 
Arsenic,  271 

acid,  275 

obtained,  271 

alloys  of,  277 
chlorides  of,  275 
detected,  273 
properties  of,  272 
oxide  of,  272 
persulphuret  of,  357 
sesquichloride  of,  275 
solution  of,  Fowler’s,  345 
tests  of,  273 

Arsenio-sulphurets,  357 
Arsenious  acid,  272 

action  of  galvanism  on,  275  [n] 
solubility,  272 
solution  made,  272  [n] 

Arsenites,  345 

Arseniuretted  hydrogen,  276 

Arterialization,  493 

Asbolin,  481 

Asphaltum,  477 

Assay,  see  Gold  and  Silver. 

Atmospheric  air,  136 

composition  of,  139 
contains  carbonic  acid,  140 
Dalton’s  theory  of,  140 
weight  of,  137 
Atomic  theory,  30 
weights,  30 
Atoms,  defined  2,  29 
elementary,  2 
figure  of,  31 
Atoms,  organic,  362 

use  of  the  term,  30 


Atropa  belladonna,  484 
alkali  of, ‘484 
Attraction,  2 

contiguous,  2 
chemical,  3 
heterogeneous,  13 
results  of,  13 
Auro-chloridrs,  358 
Auric  acid,  313 
A arum  musivum  268 
Azote,  135 

oxide  of,  141 
Azotic  gas,  135 
Azulmic  acid,  391 


BACHE’S  apparatus,  66  (n) 
Baldxoin’s  phosphorus,  77  (n) 
Balloons,  124 
Balsams,  464 

Balsam  of  Canada,  464  (n) 
of  Peru,  465 
of  Tolu,  465  (n) 

Barilla,  348 

purity  of  ascertained,  349  (n) 
Barium,  237 

chloride  of,  239 
peroxide,  use  of,  131 
pfotosulphuret  of.  239 
hydrosulphurel,  356 
peroxide,  239 
properties,  237 
protoxide,  238 
Bark,  482 
Baryta,  233 

carbonate,  350 
chlorate  of,  340 
hydrate,  233 
properties,  233 
pure  obtained,  324 
sulphate,  323 

sulpho-naphthalate,  395  (n) 
test  of  sulphuric  acid,  168 

of  carbonic  acid,  238 

Bases,  104 
Basic  water,  5 

cyanate  of  ammonia,  399 
Basis  in  dyeing,  456 
Bassorin,  474 
Battery,  voltaic,  91 
Battery's  sedative  liquor,  440  (n) 

B ’ar-berry,  acid  from,  3S8 
Beer,  487 
Bees-xoax,  460 
Beet-sugar,  469 
Benzamide,  364 — 468 
Benzoate  of  ammonia,  382 
Benzoic  acid,  381 

sublimation  of,  382 
Benzoyl , theory  of,  365 
compounds  of,  468 
properties  of.  468 
Benzule,  381  (n) 

BertholetVs  views,  23 


CAL 


BOR  535 


Berzelius,  his  symbols,  35 

theory  of  combustion,  121 
Bicarbonate  of  potassa,  348 
soda,  349 

oxide  of  ammonium,  350 
Bicar  buret  of  nitrogen,  219 
Bi-chloride  of  mercury,  304 
Bi-chromate  of  potassa,  346 
Bi-cyanuret  of  mercury , 411 
Bile,  500 

Biliary  calculi,  501 
Biniodide  of  mercury , 305 
Binoxalate  of  potassa,  371 
Binoxide  of  hydrogen,  134 
nitrogen,  143 

Bisulphate  of  potassa,  322 
Bismuth,  properties  of,  290 
chloride,  291 
magistery,  291 
oxide,  291 
sesquioxide,  291 
Bi-sulphuret  of  carbon,  220 
apparatus  for,  221  (n) 

Bitartrate  of  potassa,  384 
Bitter  almonds,  oil  of, 

hydret  of  benzoyle,  468 
Bittern,  203 
Black  dyes,  457 

flux,  271  (n) 
lead,  261 

Black,  Dr,  his  theory  of  animal  heat,  499 
Bleaching,  182 

powder,  243 

assay  of,  243  (n) 

Bladders  for  gases,  107 
Bleeding , effect  of,  496 
Blood,  494 

buffy  coat  of,  499 
coagulation  of,  495 

accelerated,  495 

colouring  matter  of,  496 
composition  of,  495 
absorbs  oxygen,  119,  498 
effect  of  chlorine  on,  496 

oxygen,  498 

of  diseases  on,  499 
peculiar  principle  in,  496 
serum  of,  497 

Blow-pipe  compound,  127,  128 
Brooke’s,  128 
Blue-dyes,  457 

Bodies,  state  of  influenced  by  heat,  37 
Boiling  point,  55 

influenced  by  pressure  55 

of  mercury,  55 

of  water,  301 

Bologna  phosphorus,  323 
Bone,  493 

composition  of,  494 
effect  of  heat  on,  494 
phosphate  of  lime,  344  (n) 
Boracic  acid,  obtained,  175 
native,  175 
properties,  176 
with  fluorine,  207 


Borates,  346 
Borax,  347 
Borofiuorides,  361 
Boron,  175 

terchioride,  195  (n) 

Boyle’s  fuming  liquor,  354 

Braude’s  experiments  on  wines,  &c>,  444 

Brandy,  488 

Brain,  494 

Brass,  297 

Brazil  wood,  458  (n) 

Bromine,  202 

and  hydrogen,  203 
action  on  combustibles,  203 

on  metals,  226 

detected,  202 
obtained,  202 
properties,  203 
Bromic  acid,  204 
ether,  452 

Bromides,  205  (n) 

Bromoform,  448  (n) 

Bronze,  2$~l 
Brooke’s  blow-pipe,  128 
Brucia,  437 
Buckthorn  berries,  486 
Buffy  coat  of  the  blood,  499 
Bulbs,  483 
Butter,  501 
Butyrine,  501 
Brunswick  green,  359 

CABBAGE,  infusion  of,  14  (n) 
Cadmium,  264 

oxide,  265  (n) 
properties,  264 
sulphuret,  265  (n) 

Caffein,  486 
Calamine,  263 
Calcination,  225 
Calcium,  240 

bromide,  244  (n) 
chloride,  243 
fluoride,  205 
phosphuret,  244 

process  for,  218  (n)  244  (ra) 

protoxide,  241 
Calculi,  biliary,  501 
urinary,  505 
varieties  of,  505 
Calico-printing , 456 
Calomel,  303 

process  for,  303  (n) 

Caloric,  absorption  of,  69 

during  evaporation,  61 

liquefaction,  51 

solution,  52 

capacity  for,  48 
apparatus  for  illustrating,  48 
cause  of  vapour,  54 
combined,  50 

conducting  power  of  bodies  for,  63 

of  liquids  and  gases,  64,  65 

conductors  of,  63 

confined  air  a bad  conductor  of,  64 


CAR 


536 


CER 


Caloric,  definitions  of,  37 

Hare’s  apparatus,  64 
Rumford’s  experiments,  63,  65 
evolved  by  increase  of  density,  50--53 

•  during  separation  of  salts,  54 

the  condensation  of  vapour, 61 

by  mechanical  pressure,  50 

expands  bodies,  38 

expansion  of  air  by,  41 

liquids,  39 

mercury,  40 

solids,  38 

•  water,  41 

general  observations  on,  37 
influences  the  state  of  bodies,  50 
influenced  by  surface,  66 

Bache’s  apparatus  for  illustrat- 

ing,  66  (n) 

latent,  50 

of  steam,  58 

made  sensible,  53 

apparatus  for  illustrating,  56 

Melloni’s  experiments,  70 
nature  of,  71 
peculiar  effect  of,  42 
polarization  of, 70 
radiation  of,  506 

■ theories  of,  70 

reflection  of,  67 
Pictet’s  experiments,  68 
radiant,  65 

sensible  made  latent,  57 
sources  of,  71 
specific,  48 

of  gases,  49 

Stark’s  experiments,  67 
Calorimeter , 48 
Calorimutor,  Hare’s,  89 
Camphogene,  463 
Camphors,  463 

common,  463 
Camphrone,  463 
Camphovinic  acid,  454 
Canada  balsam,  464  [n) 

Canton's  phosphorus,  77  (n) 

Caoutchouc,  475 
Caoutchene,  476  (n) 

Capacity  for  caloric,  48 
Capnomor,  479 
Carbazotic  acid,  392 

obtained,  392 
salts  of,  392 
Carbon,  151 

bisulphuret  of,  220 

•  process  for,  220  (n) 

a sulphur-acid,  221 

bromide  of,  205  (n) 
combustion  of,  151 
dichloride,  195  (n) 

and  hydrogen,  211 
liydroguret  of,  214 
and  iron,  227 
and  nitrogen,  219 
perchloride  of,  194 
periodide  of,  202  (u) 


Carbon,  proto-chloride  of,  194  (n) 
and  sulphur,  220 

quantity  produced  by  respiration,  498 
varieties  of,  152 
Carbonates,  characters  of,  347 
Car  bo -sulphur  et  of  hydrosulphate  of  ammo- 
nia, 357 

Carbonates,  double,  353 
Carbonate  of  ammonia,  349 
baryta,  350 
copper,  352 
iron,  352 
lime,  350 
magnesia,  351 
potassa,  347 
protoxide  of  iron,  352 

of  lead,  352 

soda,  348 
strontia,  350 
Carbonic  acid,  153 

absorbed  by  water,  155 

•  quantity,  133  [n] 

•  by  lime,  351 

apparatus  for  solidifying.  See  Plate  /. 

composition  of,  153 

effects  on  vegetation,  157 

expelled  by  heat,  351 

fatal  to  life,  155 

generated  in  combustion,  156 

liquefied  and  frozen,  157 

Mitchell’s  experiments,  157  [n] 

procured,  153 

properties  of,  154 

a product  of  respiration,  156  , 498 

quantity  produced  by  respiration,  498 

specific  gravity  of,  154 

tests  of,  156 

water  impregnated  with,  154 
Carbonic  Oxide,  154 

explodes  with  oxygen,  160 
processes  for,  159 
properties  of,  160 

Carbo-sulphuret  of  potassium,  356 

hydrosulphale  of  ammonia, 357 

Carburet,  103 

of  iron,  261 

Carburettcd  hydrogen,  light,  211 
action  of  chlorine  on,  212 
combustion  of,  212 
procured,  211 
properties  of,  212 
from  animal  bodies,  491 
Carthamin,  458  (n) 

Caromel,  470 

Cassava,  472 

Caseous  matter,  501 

Cassius,  purple  of,  314 

Cast  iron,  261  % 

Cations,  what,  98 
Cathartina,  484 
Cathode,  what,  98 
Caustic,  lunar,  337 
Cedriret,  479 
Cerasin,  474 
Cerin,  461 


CHL 


537 


COA 


Cerium,  289 

oxides,  289 

Ceruleo-sulphate  of  potassa,  457 
Cerulin,  457 
Ceruse,  See  White  lead 
Chain  of  cups,  galvanic,  90 
Chameleon  mineral,  254 
Charcoal,  152 

absorbing  power,  152 — 530 
animal,  481 
conducts  galvanism,  95 
properties,  152 

spontaneous  combustion  of,  153 
See  Carbon . 

Chemical  action,  15 
promoted,  16 
influenced,  16 — 22 
effects  of,  15 
results  of,  14 
attraction,  13 
how  exerted,  13 

modified,  19 

illustrated,  14, 16,  17 

energies  of  bodies  influenced  by  light, 74 
equivalent,  25 
Chemical  symbols,  33 — 513 
table  of,  34 
formulae,  33 
nomenclature,  102 
Chemistry , defined,  1 
foundations  of,  1 
organic, 362 
inorganic,  118 

ChevreuVs  researches  on  oils,  &c.  460 
Chio  turpentine , 464  [n] 

Chloral,  448 

Chlorates,  characters  of,  339 
Chlorate  of  baryta,  340 
potassa,  339 
soda, 349  (n) 

Chloric  acid,  192 

ether,  452  [n] 

Chlorides,  184,  225 

with  ammonia,  359 
of  gold,  314 
auro,  358 
oxy,  359 
platino,  358 
hydrargo,  358 
rhodio,  359 
of  iodine,  201  [n] 

metallic,  226 

with  phosphuretted  hydrogen,  360 
various,  195  [n] 

Chloride  of  nitrogen,  193 
bromine,  204  [n] 
ethyl,  451 
potassium,  233 
zinc,  263 
Chlorine,  180 

absorbed  by  water,  181 
action  on  ammonia,  210 

metals,  183 

• carburetted-hydrogen,  212 

antidote  to,  182  [n] 

68 


Chlorine,  action  on  olefiant  gas,  214 
condensed,  184 
effect  of  light  on,  185 
detected,  184 

explosion  of,  184,  apparatus  for, PI. II. 

with  ether,  450 

hydrate  of,  182 
nature  of,  195 
obtained,  181 
peroxide  of,  191 
supports  combustion,  182 
unaltered  by  heat,  183 
uses,  184 
weight,  182 
with  cyanogen,  41 

hydrogen,  184 

metals,  225 

nitrogen,  193 

oxygen,  189 

phosphorus,  183 

mercury,  183 

• tin,  183 

Chloriodic  Acid,  201  [n] 

Chlorites,  341 
Chloroform,  448  [n] 

Chloro  carbonic  Acid , 195  [n] 

Chloro -nitrous  Gas,  195  [n] 
Chlorophyllite,  458 
Chlorous  Acid,  191 
process  for,  192 
Choak  damp,  156 
Cholera,  effect  of  on  the  blood,  499 
Cholesterine,  501 
Cholic  acid,  501 

Christison’s  experiments  on  alcohol,  442 
table  of  strength  of  wines,  445 
Chromates,  characters  of,  345 
Chromate  of  iron,  277 — 346 

acid  from,  279 

lead,  346 
potassa,  346 
zinc,  346  [n] 

Chrome  alums,  331 
Chromic  acid,  279 
Chromium,  277 

chlorides,  280 
oxides,  278 
perfluoride,  280 
Chromule,  458 
Chromulite,  458 
Chyle,  501 

Cinchona,  varieties  of,  483 
acid  in,  388 
Cinchonia,  435 
Cinnabar,  306 

factitious,  306 
manufacture  of,  306  [n] 

native,  307 

Cinnamomic  acid,  382  [n] 

Circles,  voltaic,  85 
Citisin,  486 

Citric  acid,  process  for,  383 
from  currants,  383 

Clothing  substances, conducting  power  of, 63 
Coagulation  of  blood,  495 


CYA 


COO  538 


Coaly  gas  from,  212 — 480 
distillation  of,  480 
mines,  fire  damp  of,  212 
Coating  of  vessels , 105  [n] 

Cobalt , obtained,  268 
alloys,  270 
chloride,  269 
oxide,  269 
properties,  269 

Cobaltate  of  ammonia,  269  [n] 

Cocoa-nut  oil,  460 
Codeia,  440 
Coffee,  analysis  of,  485 
Cohesion,  2 

diminished,  19 
Coke , 153 

Colchicum  autumnale,  437 
Colcothar,  327 

Cold,  artificial  produced,  51,  60 
by  rarefaction  of  air,  50 
by  carbonic  acid,  158  [n] 

by  ether,  450 
tables  of  mixtures  for,  51 
Colocynthin,  485 
Colocynth,  485 
Colophan,  464 
Colouring  matters,  455 
Colouring  matter  of  flowers,  484 
of  fruits,  486 
of  blood,  496 
Colours,  adjective,  456 
Colour,  its  influence  on  absorption  of  calor- 
ic, 69 

of  odours,  506 

Colours,  theories  of,  74 

destroyed  by  chlorine,  182 
removed  by  carbon,  152 
substantive,  456 
Columbic  acid , 285 
Columbium,  281- 
acid  of,  285 
oxide  of,  285 
obtained,  284 
same  as  tantalum,  284 
Combination,  laws  of,  24 
accounted  for,  24 
Combining  proportion,  25 
Combustion,  121 

Berzelius’  theory  121 
Lavoisiers’  theory,  121 
in  oxygen  gas,  120 
increases  the  weight  of  bodie«,  121 
of  alcohol,  443 

Compounds  of  many  proportions,  24 
Compound  voltaic  circles,  91 
radicals,  367 
Compound  blow  pipe.  507 
Conductors  of  caloric,  63,529 
Congelation , artificial,  60 
Conicina,  484 
Conium  maculatum,  484 
Constitutional  water,  5 
Contiguous  attraction , 2 
Contraction  from  heat,  42 
Cooling , rate  of,  varied  by  surface,  66 


Copaiva,  464 

adulteration  of  detected,  465 
Copal,  465 

solution  of,  465 
Copper,  acetate  of,  379 
alloys  of,  297 
cleaning  of,  296  [n) 
chlorides,  296 

combination  with  ammonia,  328 

di-carbonate,  352 

effect  of  galvanism  on,  95 

• heat  on,  294 

ores  of,  294 
oxychloride,  359 

plates,  preservation  of,  298  (n] 
properties,  294 
scales,  328  [n] 

sulphate  of  oxides  of,  328 
sulphurets,  296 

whitened  by  arsenic,  275  (n) 
Copperas,  326 
Cork,  483 

Corn  poppy,  petals  of,  485 
Corrosive  sublimate,  304 
antidote  to,  305 
Cortical  layers,  482 
Crassamentum,4% 

Cotton , 483 

Crawford' s experiments,  53 
Crosse's  experiments,  98 
Croton  oil,  460 
Cream,  501 
Cream  of  tartar,  384 
Crenic  acid,  394 
Creosote,  478 
Croconic  acid.  373 
Crocus  of  antimony,  287 
Crude  tartar,  384 
Cryophorus,  61  (n) 

Crystallization,  agency  of  cohesion,  20 
conditions  for,  3 
connexion  of  with  chemistry,  13 
influence  of  light  upon,  7 
laws  of,  9 
promoted,  6 
systems  of,  10 
theories  of,  7 
water  of,  5 

Crystallized  tin,  265  [n] 

Crystals,  axes  of,  9 

large  forms  of  obtained,  6 
from  fusion.  4 
Cupellation,  308  [n] 

Cuticle,  494 

Currants,  acid  from,  383 
Cyanates  of  ammonia,  399 
anomalous.  399 
basic,  399 
Cyanic  acid,  398 

properties  of.  399 
Cyanodide  of  Ethyle,  452  (n) 
Cyanogen,  219 

analysis  of,  220 
compounds  of,  396 
obtained,  219 


EMU 


DOB  539 


Cyanogen,  properties,  220 
and  hydrogen,  405 
and  iron,  compounds  of,  412 

iodine,  419 

oxygen,  398 

Cyanurates,  404 

Cyanurets,  double,  of  metals,  412 
Cyanurets  of  ammonium,  409 

■ potassium,  409 

iron,  410 

palladium,  411 

silver,  411 

Cyanuric  acid,  403 
radical  of,  398 
Cystic  oxide,  433 

DALTON,  his  theory  of  atoms,  29 

ofelements,  31  (n) 

of  the  atmosphere,  140 

Daguerre,  his  invention,  507 
Daniel's  experiments,  8 
Decomposition,  18 

by  electro-magnetism,  102 

— galvanism,  96 
Decrepitation,  6 
Deflagration,  225 
Deflagrator,  Hare’s,  91 
Deliquescence,  5 

Davy,  his  galvanic  experiments,  96 

— list  of  voltaic  circles,  87  [n] 

— protector,  87 

— safety  lamp,  78 

— theory  of  galvanism,  101 

— theory  of  chlorine,  185 
Delphinia,  437  (n) 

De  Luc's  columns,  92  . 

Density,  maximum  of  water,  43 
Deoxidation,  122 
Deoxidizing  rays,  75 

substances,  their  action  on  indigo, 457 
Dextrine,  510 
Dephlogisticated  air , 118 

nitrous  air,  141 

Detonating  powders,  340,402 
Deutocarbohydrogen , 474  [n] 

its  relation  to  aldehyden,  447  (n) 
Dew,  62 

point,  63 
Diagrams,  19 

Diamond,  pure  carbon,  151 
combustion  of,  151 
Dichloride  of  carbon,  195  [n] 
sulphur.  195  [n] 

Differential  thermometers,  46 

Diffusion  of  gases,  Mitchell’s  exp’ts  on, 497 

Diffusiveness  of  gases,  140 

Dilatation  of  air , 41 

Dippel's  oil,  491,502 

Diseased  blood,  499 

Disinfecting  liquid,  349  [n] 

Distillation,  132 

destructive,  368 

of  vegetables,  477 

Distilled  water , 162 
Dobereiner's  lamp,  125 


Double  elective  affinity,  17 
carbonates,  353 
fluorides,  361 
iodides,  360 
sulphates,  330 
Dragon's  blood,  465 
Drummond's  light,  76 
Ductile  metals,  223 

Dumas'  process  for  carbonie  ©xide,  159 

Dutch  gold,  297 

Dutrochet,  experiments  of,  49’([ , 

Dyeing,  456 
Dyes,  black,  457 
blue,  457 
red,  456 
with  indigo,  458 

EARTHS,  alkaline,  228 
bases  of,  228,  237 
Ebullition , 56 
Efflorescence,  5 

effects  of,  21 

Effluvia  of  putrescent  substances,  492 
Elaine,  460 

Elastic  gum,  see  Caoutchouc,  475 
Elaterium,  485 
Elasticity , effects  of,  21 

increased  by  heat,  21 
influences  results,  22 
Elatin,  485 
Elective  affinity,  17 
Electricity,  79 

and  galvanism,  identity  of,  85 
action  on  ammonia,  209 

on  albumen,  493 

by  induction,  81 

Faraday’s  theory  of,  81 

nature  of,  94 

quantity  and  intensity,  94 
sources  of,  84 
theories  of,  79,  81 
voltaic,  85 

Electrical  battery,  84 
Electro-chemical  equivalents  100, 

decomposition,  101 
Faraday’s  theory  of,  101 

Electrodes,  98 
Electrolytes,  only  excite,  99 
Electrolytic  action,  99 
Electrolyze,  98 
Electromagnetism,  102 
Electrometer , 80 

Volta's,  100  (n) 

Electrophorus,  84 
Electro-positive  bodies,  101 
negative,  101 
Erithrogen,  497 
Ethylide  of  potassium , 510 
Elements,  chemical,  37 
Emetic  tartar,  385 
Emmet's  process  for  formic  acid,  374 
Emetina,  437  [n] 

Emulsin,  475 
Eliquation , 309  [n]  300 
Enamel , 178  (n) 


FRU 


FEC  540 


Endosmose , 497 
Epsom  salts,  325 
Equivalents,  chemical,  25 
of  compounds,  25 
determined,  28 
electro-chemical,  100 
uses  of,  28 
Erythrin,  455 
Erythrogen,  497 
Ethal,  448 
Ethyle,  509  . 

Ethyl,  451 

chloride  of,  451 
cyanodide  of,  452  (n) 

sulphuret  of,  452 
Ether,  448 

sulphuric,  448 
purification  of,  449 

Philip’s  process  for,  449  (n) 

production  of  cold  by,  57 
explodes  with  oxygen  and  with  chlo- 
rine, 450 

action  on  oxides,  451 
base  of,  451 
hydrochloric,  451 
nitric,  453 
oxalic,  453 
cenanthic,  454 
thialic,  452 
hydrocyanic,  452  (n) 

sulphohydric,  452  (n) 

chloric,  452  (n) 
iodic,  452 
sulphocyanic,  452 
Ethers,  theory  of,  365 
Etheroxalate  of  potassa,  453  (n) 

Ethionic  acid,  395 
Ether oxamide,  468 
Ethiop's  mineral,  307 
Euchlorine,  189 
Eudiometry,  137 

Gay  Lussac’s  method,  145  (n) 
Eudiometer , 137 

Doebereiner’s,  139 
Priestley’s,  139 
Ure’s,  138  (n) 

Volta’s,  138 
Eupion,  476 — 477 
Evaporation,  4,  57 
Exosmose,  497 
Expansion,  38 

of  air,  rate  of,  42  (n) 

Extractive,  477 
Extractum  Saturni,  379 


FARADAY,  his  experiments,  93 

electrical  investigations,  81 

induclometer,  82 

new  terms,  98 

theory,  81,  82,  101 

volta-electrometer,  100  (n) 

Fat,  502 
Feathers,  494 
Fecula , 471 


Fermentation,  487 

acetous,  487 — 489 
panary,  490 
vinous,  487 

Fermented  liquors,  strength  of,  444 
Ferro-cyanogen,  compounds  of,  412 
Ferro-cyanurets,  413 

decomposed  by  heat,  413 
with  two  basic  metals,  416 
Ferrocyanuret  of  ammonium,  413 
mercury,  415 
potassium,  413 
potassium  and  iron,  416 

Fibrin,  492 
Finery  cinder,  256 
Firedamp  of  mines,  212 
Fireworks  without  smell,  &c.  125 
Fixed  acids,  382 
oils,  459 

effect  of  air  on,  459 
spontaneous  combustion  of  459 
Flame,  what,  213 

light  and  heat  of,  77 
tinged  by  selenium,  179 
red  and  green,  336  (n) 

Flour,  wheat,  471 
Flowers  of  sulphur,  162 

colouring  matter  of,  484 
Fluidity,  caloric  of,  50 
Fluoboric  acid,  207 
obtained,  207 
properties,  207 

Fluids,  imperfect  conductors,  65 
Fluoric  acid,  see  Hydro-fluoric,  205 
Fluosilicic  acid,  208 

singular  appearance,  208 
Fluorides,  double,  361 
Fluoride  of  calcium,  205 
Fluorine,  205 

action  on  metals,  226 
Fluor  spar,  205 
Flux,  black,  271  (n) 

white,  333  (n 
Fly  powder,  272 
Forbes's  experiments,  70 

spark  from  magnet,  102 
Formic  acid,  373 
Formo-benzoilic  acid,  395 
Forms  of  crystals,  9 
Formulce,  chemical,  33,  513 
abbreviated,  35 
Fowler's  solution,  345 
Freezing  mixtures,  51 

apparatus  for,  53  (n) 
in  vacuo,  60 
Leslie’s  method,  60 
of  mercury,  53 

by  carbonic  acid,  157 

bv  ether,  450 

Freezing  and  boiling,  of  water  and  ether, 
450  * 

Frost,  62 

bearer,  61 

Friction,  light  from,  77 
Fruits,  486 


GAS 


541 


GOL 


Fruits , acids  of,  486 

contain  sugar,  486 
colouring  matter  of,  486 
Fulminating  gold,  313 
platinum,  318 
powder,  334 
silver,  310 
mercury,  402 
Fuming  liquor,  267 
Furnaces,  111 
Fusibility  of  metals,  223 
Fusion,  watery  of  crystals,  6. 


GAL  AC  TIN,  461 

Galena,  298 

Gallic  acid  obtained,  387 
properties,  387 
use,  388 

precipitates  by,  387 

Galls,  387 

Galvanic  arrangements,  85 
battery,  89 

Hare’s,  89 

pile,  90 
trough,  90 

Galvanism,  see  Voltaic  electricity,  85 
excitement  of,  85 
and  electricity,  identity  of,  94 
decomposes  water,  96,  131 
theories  of,  92 

Gases,  equivalent  weights  of,  32 
expansion  of  by  heat,  42 
condensible  by  pressure,  118 
apparatus  for  experiments  on,  107 
method  of  weighing,  116 

transferring,  113 

quantities  of  absorbed  by  water,  133 

00 

purity  ascertained,  138 
from  gun-powder,  335 
give  out  their  latent  heat  by  compres- 
sion, 50 

ratios  of  combining  vols.  33 

calculated,  33 

specific  heat  of,  49 
specific  gravities  of,  32 
tendency  to  become  thoroughly  mix- 
ed, 127 

general  law  of  their  union  by  vols.  31 
diffusion  of,  Mitchell’s  exp’ts,  497 
tend  to  mix  together,  127 
liquefaction  of,  117 
solidification  of,  157 
as  bottles,  107 
bags,  107 
holder,  109 

Gas,  what,  105 

ammoniacal,  208 
arsen  in  retted  hydrogen,  276 
azotic,  or  nitrogen,  134 
binoxide  of  nitrogen,  143 
light  carburetted  hydrogen,  211 
carbonic  acid,  153 
carbonic  oxide,  159 


Gas,  carburetted  hydrogen,  211 
coal,  480 
chlorine,  180 
chloronitrous,  195  (n) 

cyanogen,  219 
fluoboric  acid,  207 
hydriodic  acid,  198 
hydrochloric  acid,  184 
hydrogen,  122 
hydrosulphuric  acid,  214 
— — properties  of,  215 

action  on  metals,  215 

* salts  of,  215 

hydro-zincic,  327  (n) 
hydrotelluric  acid,  293  (n) 
nitric  oxide,  143 
nitrogen,  134 
nitrous  acid,  146 
nitrous  oxide,  141 

■ purity  ascertained,  142 

oil,  481 
olefiant,  213 
oxygen,  118 

oxymuriatic  acid.  See  Chlorine  gas 
phosgene,  195  (n) 
phosphuretted  hydrogen,  217 
protoxide  of  nitrogen,  141 
seleniuretted  hydrogen  217 

sulphuretted , 214 

sulphurous  acid,  163 
Gas  lights,  481 
Gay  Lussac's  theory,  31 

apparatus  for  hydrogen,  123 
method  of  analysis  of  gases,  145  (n 
Gasometer,  108 

mercurial,  110  (n) 

Gelatine,  properties  of,  493 
test  of,  493 

Glaser's  polychrest  salt,  334 
Glair  in,  475  (n) 

Glass,  178 

action  of  hydrofluoric  acid  on,  206 
annealing,  178 
of  antimony,  287 
of  borax,  347 
pastes,  178  [n] 

etching  on,  206 
method  of  colouring,  17S  [n] 

varieties  of,  178 
vessels,  acted  upon,  178 
Glauber's  salt.  See  Sulphate  of  soda. 
Glauberite,  330 

Glucina,  method  of  obtaining,  249 
distinguished,  249 
properties,  249 
Glucinium,  248 

sesquioxide  of,  249 
Glue,  493 
Gluten,  471 — 474 
Glutin,  475 
Glycerin,  471 
Gold,  malleability  of,  312 
alloys  of,  315 
chlorides  of,  314 
fulminating,  313 


INS 


HEA  542 


Gold,  oxides  of,  313 
pure,  312 — 314 
percyanuret  of,  412 
precipitants  of,  314 
revival  of,  314 
solution  in  ether,  314 — 451 
standard  of  U.  S.,  315  (n) 
separated,  312 — 329  [n] 
cleaned,  296  (n) 

assay  of,  316 
powder,  316 
effect  of  galvanism  on,  95 
mosaic,  268 — 297  (n) 

Dutch,  297 
fineness  of,  316 
colour  destroyed,  315 
ductility  destroyed,  315 
analysis  of  alloys  of,  315 
Gooseberries,  acid  from, 393 
Goniometers , 8 
Graduated  vessels,  107 
Graham's  experiments,  140 
on  alcohol,  442 
Graphite,  261 
Gravel,  urinary,  505 
Green  fire,  336  (n) 

Gregory’s  process  for  hydro-chlorate  of 
morphia,  439  (n) 

Gravitation,  2 
Gravity,  influence  of,  23 

specific,  effect  of  chemical  union  on,  16 

of  gases,  32,  114,  116 

of  solids,  115 

of  powders,  115 

of  liquids,  116 

water,  standard  of,  114 
Gum  resins,  466 — 482 
fetid,  466 
cathartic,  467 
sedative,  467 
Gums,  473 

Gunpowder,  composition  of,  334 
Gypsum,  325 

HJEMA  TITE,  red,  257 
Hcemaiin,  45S  (n) 

Half  equivalents,  26 
Hare's  apparatus,  64 
blow  pipe,  127 
calorimotor,  89 
reservoir  for  hydrogen,  123 
Hair,  494 

Haloid  salts,  105,  358 
Hassenfratz,  his  theory  of  animal  heat,  499 
Haiiy's  theory,  7 
Heat.  See  Caloric,  37 
animal,  498 
Black’s  theory  of,  499 
of  flame,  77 
guarded  against,  69 
nature  of,  71 
latent,  50 

and  cold,  sensations  of,  37 
operation  of  on  animal  bodies,  491 
polarized,  70 


Heat,  influences  affinity,  22 
radiant,  65 
sources  of,  71 
specific,  48 

transfer  of  prevented,  64 
theories  of,  70 
Henry’s  apparatus,  58  (n) 

HeSvene,  476 
Hellot’s  ink,  270  (n) 

Hemlock,  484 

Heterogeneous  attraction,  13 
Hircine,  502 
Hog's  lard,  502 
Homberg’s  phosphorus,  242 
pyrophorus,  330 
Honey,  471 

stone,  375 
Hoofs,  494 
Hops,  486 
Hordein,  473 
Horn  silver,  310 
Horns,  494 
Humus,  490 
Hydrate,  what,  133 

of  hypophosphorous  ucid,  172 
Hydriodates,  199 
Hydriodic  acid,  198 
properties,  199 
decomposed,  199 
test  of,  200 
use,  200 

Hydrobromic  acid,  203 
process  for,  204 
properties,  204 
Hydro  carburet,  211 
Hydrochlorate  of  ammonia,  353 
native,  354 

Hydrochloric  acid,  184 

process  for,  185,  187  (n) 
absorbed  by  water,  186 
apparatus  for,  187  (n) 
composition,  189 
liquid,  187 
recognized,  189 
theory  of,  185 

Hydrocyanate  of  ammonia,  409 
Hydrocyanic  acid,  405 

with  metallic  oxides,  409 
Hydroferrocyanic  acid,  412 

and  metallic  oxides,  413 

Hydrofluoric  acid,  205 

action  on  glass,  206 

on  metals,  207 

Hydrofluate  of  ammonia,  354 
Hydrofluates,  207 
Hydrofluorides,  361 
Hydrometers,  443 

INDIAN  CORN,  sugar  of,  470 
Indigo,  457 
Indigogen,  457 
Intermediate  bodies,  441 
Ink,  indelible,  338,  new,  509 
printers’,  459  (n) 

Insoluble  cyanurets,  409 


543 


LIM 


KIN 

Insoluble,  chloral,  448 
Inulin,  473 
Iodic  ether , 452 
Iodine,  nature  of,  198 

detection  of,  198 — 508 
in  sea  water,  508 
oxide  of,  200 
and  chlorine  201 
and  nitrogen,  201 
and  oxygen,  200 
and  phosphorus,  198 
sources  of,  196 
test  of,  198 
lodurets,  198 
Iodous  acid,  200 
Iridium.  320 
Iron , 256 

alum,  331 

action  of  water  on,  256 

of  nitric  acid,  257  (n) 

of  sulphuric  acid,  257 

acetate  of,  378 
bisulphuret  of,  260 
black  oxide,  258 
carbonate  of  protoxide,  352 
carburets  of,  261 
cast,  261 

combustion  of  in  oxygen,  120 
with  carbon,  227,  261 
chlorides,  258 
chromate  of,  277 

acid  from,  27 

and  cyanogen  constitution  of  the  com- 
pounds of,  412 
cyanuret  of,  410 
fluorides  of,  259  (n) 

gray,  261 

oxychlorides  of,  359 
phosphurets  of,  260  (n) 

properties,  256 
protiodide  of,  259 
protochloride  of,  258 
protoxide  of,  257 
sesquiferrocyanuret  of,  415 
process  for,  415 
sesquioxide  of,  257 
sesquichloride  of,  258 
sesqu iodide  of,  259  (n) 
sulphate  of  protoxide,  326 
test  of,  389 
varieties  of,  261 
Isinglass,  493 
Isomeric  bodies,  36 
Isomorphism,  12 

advantages  of,  12 

JELLY  obtained  by  pectic  acid,  393 

Jackson,  his  lamp.  See  Frontispiece. 

KELP,  348 
Kermes,  288 
King's  yellow,  277 
Kinic  acid,  388 


LABARRAQUE’S  liquid , 349  (n) 

Lac,  466 

varieties  of,  their  composition,  466  (n) 
solvent  for,  454  (n) 

Laccin,  466 
Lactates,  380 
Lactic  acid,  380 — 503 
Lactucarium,  467  (n) 

Lakes,  456 
Lamp,  safety,  78,  213 
aphlogistic,  78 
Jackson’s,  120  (n) 
black,  481 

Lapis  lazuli,  colouring  matter  of,  236  (n) 
Latanium,  320 
Latent  heat,  50 

made  sensible,  53 
Lavoisier' s theory,  121 
Laws  of  combination,  24 
advantage  of,  27 
Lead,  acetate  of,  379 

action  of  water  on,  298 
alloys  of,  300 

carbonate  of  protoxide,  352 
poisonous,  299  (n) 
chloride  of,  300 
detected,  299 
oxides  of,  298 
oxychlorides  of,  359 
peroxide  of,  300 
properties  of,  298 
purified,  298 

salts  of,  poisonous,  299  (n) 
solvent  of,  298 
subacetate  of,  379 
sugar  of,  379 
Leather,  389 
Legumin,  475  (n) 

Leslie's  method  of  freezing,  60 

experiments  on  radiation,  66 
photometer,  75 
Leucine,  492 
Leyden  jar,  83 

Libavius,  fuming  liquid  of,  267 
Lichenin,  473 

Liebig's  compound  radicals,  367 
Light,  71 

analysis  of,  74 
chemical  effects  of,  75 
magnetical,  75 
double  refraction  of,  73 
Drummond’s,  76 
of  flame,  77 

influence  on  vegetation,  76 
from  percussion,  &c.,  77 
polarization  of,  73 
reflection  of,  72 
refraction  of,  72 
Lignin,  473 
Lime,  acetate  of,  878 

bone  phosphate  of,  344  (n) 

carbonate  of,  350 
chloride  of,  243 
fluate  of,  205 
hydrate  of,  241 


MER 


MAN  544 


Lime , hydrochlorate,  242 
light  of,  76 
milk  of,  241 
nitrate,  336 
oil  of,  242 
oxalate  of,  372 
phosphates  of,  344 
phosphuret,  244 
properties  of,  241 
solubility  of,  241 
sulphate  of,  325 
test  of,  242 
water,  241 
Liquefaction,  51 

of  gases,  117 

• chlorine,  184 

carbonic  acid,  157 

apparatus  for,  Plate  I. 

Liquids,  expansion  of  by  heat,  39 
evolve  heat,  53 

manner  in  which  they  conduct  heat, 
64 

specific  gravity  of,  116 
Liquorice,  sugar,  471 
Lithia,  discovery  of,  237 
distinguished,  237 
obtained,  237 
Lithic  acid,  504 
Lithium,  237 

chloride  of,  237  (n) 
fluoride  of,  237  (n) 

Litmus,  455 

Lixivium,  what,  197  [n] 

Logometric  scale,  513 
Loco  foco  matches,  171  [n] 

Lunar  caustic , 309,  337 
Lupulin,  486 

MAGISTERY  of  bismuth , 291 
Magnesium,  245 

chlorides  of,  246 
hydrate,  246  [n] 
protoxide  of,  245 
Magnesia,  246 

calcined,  246  (n) 

carbonate  of,  246  (n) 

sulphate  of,  325 

. adulteration  of,  326  (n) 

Magnesite , 351 
Magnet, * Electro,  102 
spark  from,  102 
decomposition  by,  102 
Magnetism,  Electro,  102 
Magnetizing  rays,  75 
Maize,  formic  acid  from,  374 
Malachite,  352 
Malic  acid,  382 
Malt,  487 

Manganate  of  potassa,  254 
Manganese,  251 

acids  of  with  potassa,  give  different 
colours  with  water,  254 
in' blood,  496 
alum,  331 
perchloride,  255 


Manganese,  perfluoride,  255 
peroxide,  252 

uses  of,  253 

protochloride  of,  255  (n) 
protosulphuret  of,  256  (n) 
salts  of,  252 
red  oxide  of,  253 

composition,  253 

Manganic  acid,  254 
Manipulation  with  tubes,  113 
Manna,  471 
Mannite,  471 
Maple  sugar,  469 
Marble,  153 

MarceVs  apparatus  for  boiling,  56  (n) 

for  freezing,  57  (n) 

Margaric  acid,  391 

Margarine,  390 — 502 

Marsh's  method  of  detecting  arsenic,  274 

Massicot,  298 

Mastic,  465 

solvent  for,  454  (n) 

Matches  for  instantaneous  light,  171  (n) 

Matter,  quantity  of,  22 

Measure  of  affinity,  23 

Meat,  preservation  of,  process  for,  491  (n) 

Mechanical  division , advantage  of,  16 

Meconates,  387 

Meconia,  440 

Melam,  397 

converted  into  cyanuric  acid,  397 
Melamin,  396 

combinations  of,  397 
Mellite,  375 
Mellitic  acid,  375 
Mellon,  220  (n ) 396 
Melloni's  experiments,  70,  74 
Mercaptan,  452 

Mercurial  trough , Newman’s,  110  (n) — 

163  (n) 

Mercury,  acetate  of,  379 
adulteration  of,  301 
action  of  chlorine  on,  303 

oxygen,  225 

alloys  of,  307 
bichloride  of,  304 

process  for,  304  (n) 

bicyanuret  of,  411 
chlorides  of,  303 
congelation  of,  301 

apparatus  for,  53  (n) 

by  carbonic  acid,  158  (n) 

detected,  305 
expansion  of,  40 
ferrocyanuret  of,  415 
fulminating,  402 
iodides  of,  305 
oxides  of,  302 
pernitrate  of 
peroxide  of,  302 

action  of  water  on,  303 

protacetate  of,  379 
protochloride  of,  303 
prussiate  of 
purified,  301  (n) 


MOL 


545 


NIT 


Mercury,  specific  gravity  increased  by  con- 
gelation, 301 

sulphates  of  oxides  of,  329 
sulphurets  of,  306 
with  potassium,  307 
Mesite,  455 
Mesoxalic  acid,  427 
Metals,  acids  from, 225 

action  of  acids  on,  228 

bromine,  226 

carbon,  227 

chlorine,  225 

fluorine,  226 

hydrogen,  227 

iodine,  226 

phosphorus,  227 

sulphur,  226 

sulphuretted  hydrogen,  215 

alloys  of,  224,  227 
amalgams,  224,  228 
classification  of,  228 
conduct  heat,  222 

decomposing  water  at  a red  heat,  229, 
251 

double  cynnurets  of,  412 
enumeration  of,  222 
fusibility  of,  223 

fused  and  ignited  by  galvanism,  95 
malleable,  222  (table  m) 
not  essential  in  Voltaic  circles,  8S 
oxidation  of,  225 
qualities  altered,  224,  228 
salifiable  bases  from,  225 
seleniurets  of,  227 
specific  gravities  of,  222 
speculum  metal,  297  (n) 
sulphurets  of,  226 
tenacity  of,  223 
Metallic  alloys , 227 
chlorides,  226 
phosphurets,  227 
seleniurets,  227 
sulphurets,  226 
Metaphosphoric  acid,  174 
peculiarity  of,  175 
Metaphosphates,  342 
Meteoric  stones  contain  nickel,  256 
Microcosmic  salt,  343 
Milk,  501 

Minder  erus' s spirit,  378 
Mineral  chameleon , 254 
green,  352 
yellow,  359 

Mineral  waters,  separation  of  salts  from, 
21  (n) 

Minium , 299 

Mitchell's  process  for  phosphuret  of  calcium, 
218  [n] 

experiments  on  passage  of  air,  497 
Mitscherlich' s discovery,  12 
Mixture,  frigor-ific,  51 
Molasses,  469 

Molybdenum,  hydrate  of,  282 
ore  of,  282 
obtained,  232 


Molybdenum,  oxides  of,  282 
properties,  282 
sulphurets,  283 
Molybdic  acid,  282 
Molybdo- sulphurets,  357 
Mordant,  what,  456 
Morphia,  438 

acetate  of,  439 
detection  of,  438 
hydro-chlorate  of,  439 
process  for,  439  [n] 

Morrichini,  his  experiments,  75 
Mosaic  gold,  268,  297  [n] 

Mucin,  475 
Mucus,  503 

Multiples,  law  of  combination  in  simple,  25 
Murexan , 433 
Murexid,  431 

Muriates.  See  Hydrochlorates,  353 
Muriatic  acid.  See  Hydrochloric,  184 
impurities  of,  188 
prepared,  187 
Muscles,  494 
Muscovado  sugar,  469 
Must,  488 
Mustard,  486 
Mykomelinic  acid,  427 
Myricin,  461 
Myrtle  wax, 461 


NAILS,  494 
Narceia,  440 
Narcotina,  437 
Naphtha,  477 
Naphthalic  acid,  480  (n) 

Naphthaline,  479 
Nascent  state,  what,  21 
Nature  of  chlorine,  195 
Neutral  compounds,  25 

vegetable  principles,  467 
Neutralization,  14 
Newman's  trough,  110  (n) 

Nickel,  270 

chloride  of,  271  (n) 

detected,  270  (n) 

properties,  270 
protoxide,  271 
Nicotin,  441 
Nightshade,  484 
Nitrates,  characters  of,  332 
of  baryta,  335 
copper,  336 
lime,  336 

oxide  of  ammonium,  335 
oxides  of  mercury,  336 
potassa,  333 
protoxide  of  copper,  336 
Nitrate  of  silver,  337 
of  soda,  335 
of  strontift,  336 
Nitre,  333 

decomposed,  333 
Nitric  acid,  147 

action  on  animal  matter,  149 


69 


OIL 


546 


OXI 


Nitric  acid,  action  on  fixed  oils,  459 

iron,  257  (n) 

lead,  300 

metasl,  150 

phosphorus,  150,  174 

sugar,  470 

volatile  oils,  462 

boiling  point  of.  149 
decomposed,  150 
detected,  509 
effect  of  light  on,  149 
oxide  of,  1-13 
properties  of,  149 

proportion  of  real  acid  in  100  parts, 
523. 

prepared,  147,  148  (n) 

purified,  148 
Nitric  ether,  453 
Nitrites,  339 
Nitrogen,  134 

in  animal  substances,  490 
analysis  of,  143 
detected,  509 
process  for,  134 
and  oxygen,  135 
— carbon,  219 
binoxide  of,  143 

properties,  144 

use  of,  145 

chloride  of,  193 
phosphuret  of,  220  (n) 

protoxide  of,  141 

quantity  absorbed  by  water,  133  (n) 
quadrochloride  of,  193 
sulphuret  of,  221  (n) 

supposed  base,  135 
teriodide  of,  201 
Nitronaphthalese,  480 
Nitrous  ether , 453 
Nitrous  air,  dephlogisticated,  141 
acid,  146 

properties,  147 

gas,  143 

Nitro -hydro chloric  acid,  189 

sulphuric  acid,  329,  337 

Nitrous  oxide,  141 

analysis  of,  143 
absorbed  by  water,  133  (n) 

Nitrous  turpeth,  337 
Nobilli's  experiments,  70 
Nomenclature,  102 
Noyeau.  485 
Nux  vomica,  437 

OERSTED'S  discoveries,  102 
(Enanthic  ether,  454 
Octohedral  system,  10 
Oil  gas,  481 

apparatus,  481  (n) 

cocoa  nut,  460 
croton,  460 
olive,  460 
palm,  460 
of  tartar,  348 
Oil,  of  turpentine,  462 


Oil,  of  wine,  452 

almonds,  485 

Oils,  action  of  acids  on  fixed,  459 
action  of  nitric  acid  on,  459 
action  of  alkalies  on,- 460 
combustion  of,  469 
drying,  459 
soap  from,  390 
spermaceti,  503 
train,  503 
volatile,  461 
watchmaker’s  460  (n) 
sweet  principle  of,  471 
Oily  acids,  390 

Oleaginous  substances,  458 — ■ 502 
Olefiant  gas,  213 

action  of  chlorine  on,  214 
properties  of,  214 

quantity  absorbed  by  water,  133  (n) 
Oleic  acid,  391 
Olein,  391,  502 
Oleine,  460 
Olive  oil,  460 
Opium,  467 

alkali  of,  438 
detected,  438 
process  for,  438 
acid  in,  386 
substances  in,  440  (n) 

Organic  chemistry,  362 
principles,  362 

classes  of,  363 

matter  in  water,  132  (n) 

Organic  and  Inorganic  compounds , 
distinction  between,  362 
Orpiment,  277 
Osmazome,  493 
Osmic  acid,  319 
Osmium,  319 

oxide  of,  319 

Oxalate  of  ammonia,  371 
lime,  372 

calculi,  369,  505 

potassa,  371 
Oxalic  acid,  369 

composition  of,  371 
decomposed,  371 
distinguished,  370 
from  tannic  acid,  389 
properties  of,  3/0 
theory  of  its  production,  370 
poisonous,  370 
in  vegetables,  369 
Oxalovinic  acid,  454 
Oxalurate  of  ammonia,  428 
Oxaluric  acid,  428 
Oxamide,  467 

analysis  of,  468 
obtained,  467 
properties  of,  467 
action  of  sulphuric  acid  on,  467 
Oxide,  carbonic,  159 

quantity  absorbed  by  water,  133  (n) 

. by  charcoal,  530 


cystic,  433 


PAR 


547 


PHO 


Oxide , nitric,  143 

nitrous  absorbed  by  water,  133  (n) 

by  charcoal,  530 

of  phosphorus,  171 

— process  for,  172  (n)  508 

of  selenium,  179 
uric,  433 
xanthic,  433 

Oxides,  nomenclature  of,  103 
reduction  of,  225 
sesqui,  102 
Oxy- chlorides,  359 
of  copper,  359 
lead,  359 
iron,  359 

Oxygen,  absorbed  by  the  blood,  119 

by  combustible  bodies,  121 

by  tannic  acid,  389 

action  of  on  blood,  498 
compounds  of  combustible  bodies  with, 
122 

of  chlorine  with,  189 

derivation  of,  103 
diminished  in  combustion,  120 

by  respiration,  498 

explosion  with  ether,  450 

loss  of  compensated,  141 

not  the  sole  principle  of  acidity,  122 

produces  oxides  and  acids,  122 

union  with  hydrogen  forms  water,129 

nitrogen,  141 

chlorine,  189 

gas,  118 

its  effect  on  indigo,  457 
properties,  119 
procured,  118 

combustion  of  carbon  in,  120 

of  phosphorus,  120 

quantity  absorbed  by  water,  133  (n) 

— by  charcoal,  530 

required  for  combustion  of  woods, 

484 

supports  life,  119 

Oxyhydrogen,  blow  pipe,  128, 507 
Oxyiodides , 360 

Oxymuriatic  acid.  See  Chlorine. 

Oxy  muriates.  See  Chlorates. 

Oxy  salts,  320 

PALLADIO- CHLORIDES,  358 
Palladium,  319 

cyanuret  of,  411 
oxides  of,  319 
Palm  oil , 460 
Panary  fermentation,  490 
Pancreatic  juice,  500 
Paper,  test,  455,  370 
Parahanic  add,  428 
Paracyanogeu,  220  (n) 

Paraffin,  477 
Paranaphthaline,  480 
Parillia,  440 
Parts  of  plants,  482 
Particles  of  bodies,  2 
integrant,  13 


Pectic  acid,  393 

obtained,  393 
Pectin,  393 
Pearlash,  347 

sources  of,  348  . _ 

quantity  of  alkali  in,  ascertained,  158 
Pearl-white,  291 

powder,  291  (n) 

Pelletier  and  Caventou  s process  for  Cm- 
chonia,  435  (n) 

Perchlorates,  341 
Perchloric  acid,  193 
Perchloride  of  carbon,  194 
of  manganese,  255 
of  phosphorus,  195  (n) 

Percussion,  light  from,  77 
Percyanuret  of  gold,  412 
Perfluoride  of  manganese,  255 
Perfumed  essences,  462 
Periodic  acid,  201  (n) 

Periodide  of  carbon,  202  (n) 

Permanganic  acid,  254 
Peroxide  of  hydrogen,  134 
Persulphuret,  of  arsenic,  277 

hydrogen,  216 

Petroleum , 477 
Peru,  balsam  of,  465 
Pewter,  268,  288,  300 
Phlogiston,  121,  122 
Phosphates,  characters  of,  342 
detected,  342 
Pitch,  464 

Plating  of  copper,  312 
Portfire,  335  (n) 

Phenicin,  457 
Phosphorescence,  78 
Phosphori,  solar,  76 
Phosphoric  acid,  173 

distinguished,  174 
glacial,  175 
prepared,  174 
matches,  171  (n) 
test  of,  174 
union  with  bases,  174 
Phosphorous  acid,  173 
Phosphorus,  169 

action  on  metals,  227 

of  nitric  acid  on,  174 

Baldwin’s,  77  (n) 

Bolognian,  323 
bromides  of,  205  (n) 

Canton’s,  77  (n) 
characters  of,  169 
combustion  in  oxygen,  120.  170 

■ slow,  170 

. under  water,  340 

effect  of  light  on,  171 
equivalent  of,  171 
inflames  in  rarefied  air,  1 /0 
oxide  of,  171 
Verrier’s  process,  172  (n) 

Botger’s  508 

solution  in  ether,  171 
union  with  chlorine,  183 
hydrogen,  217 


POT 


548 


PRO 


Phosphorus,  union  with  iodine,  198 

oxygen,  171 

use  in  eudiometry,  139 
Phosphovinic  acid.  395  (n) — '454 
Phosphuret  of  calcium,  218  (n) 
of  nitrogen,  2-0  (n) 

Phosphurets , metallic,  227 
Phosphuretted  hydrogen , 217 
prepared,  217 
chlorides  with,  360 
combustion  in  oxygen,  219 
effect  of  light  on,  219 
salts  of,  355 

Photogenic  drawing,  311  (n)  507 
Picamar,  479 
Picromel,  501 
Pinchbeck , 297 
Pictet's  experiments , 68 
Pistol , electrical,  125 
Pittacal,  479 
Plants,  parts  of,  482 

respiration  of,  511 
juices  of,  482 
Platina-mohr,  377  (n) 

P latino -chlorides,  358 

biniodide  of  potassium,  360 

of  hydrogen,  360 

Platinum,  316 

action  on  hydrogen  and  oxygen  gases, 
316 

on  alcohol, 377  (n) 

on  carbonic  oxide,  160 

chlorides  of,  317 
conducts  caloric  slowly,  316 
ethereal  solution  of,  451 
fulminating,  318 
iodide  of,  318 
oxides  of,  317 
properties  of,  316 
spongy,  316 
sulphurets  of,  318 
test's  of,  318 
Plesiomorphism,  13 
Pneumato- chemical  trough,  108 
mercurial,  110,  163  (n) 

Polarization  of  heat,  70 
of  light,  73 
Poles,  voltaic,  98 
Pollenin,  475  (n) 

Polychroite,  458 
Poppy,  485 
Potash,  caustic,  232 
Potassa,  232 

acetate  of,  378 

action  on  organic  compounds,  368 

bicarbonate  of,  348 

binoxalate  of,  371 

bisulphate  of,  322 

bitartrate  of,  384 

carbonate  of,  347 

chlorate  of,  339 

distinguished,  232 

affords  oxygen,  119 

action  on  inflammables,  339 

of  sulphuric  acid  on, 340 


Potassa , chromates  of,  346 
croconate  of,  372 
fusa,  232 

etheroxalate  of,  453  [n] 
iodate  of,  341 
manganate  of,  254 
nitrate  of,  333 
preparation  of,  232 
properties  of,  232 
proto-hydrate  of,  232 
pure,  prepared,  232  [n] 
purified,  232 
quadroxalate  of,  372 
bistearate  of,  390 
sulphate  of,  322 
bisulphate,  322 
sulpho-indigotate  of  395 
tartrates  of,  385 
Potassium,  229 

apparatus  for,  528 
boro-fluoride  of,  361 
bromide,  of 233  [n] 
carbo-sulphuret  of,  356 
carburet  of,  233  [n] 
chloride  of.  233 
compounds  of,  231 
cyanuret  of,  409 

■ process  for,  410 

decomposes  water,  231 
ferrocyanuret  of,  413 
fluoride  of,  233  [n] 
and  hydrogen,  233 
hydro-sulpiiuret  of,  356 
iodide  of,  233 
phosphurets  of,  234  [n] 

platino-biniodide  of,  360 
processes  for,  230 
properties,  230 
seleniurets  of,  234  [n] 
sulphurets  ol,  234,  234  [n] 
and  iron,  ferrocyanuret  of,  416 
tersulphuret  of,  234 
Potatoes,  483 
Powder,  fulminating,  334 
gun,  334 

with  chlorate  of  potassa,  340  (n) 
Precipitate,  red,  302 

process  for,  302  (n) 

Precipitates,  apparatus  for  drying,  59 
Precipitation,  18 

Preservation  of  animal  substances,  491 
Pressure,  influences  the  boiling  point,  56 

crystallization,  6 

chemical  action,  23 

Prevost's  theory,  71 
Priestley's  method  of  analysis,  139 
Primitive  forms,  8 
Printers'  ink , 459  (n) 
types,  288 

Prismatic  colours,! A 
systems,  II 
Proof  spirit,  443 
Proportion,  what,  25 
Proportions  in  which  bodies  combine,  23 
compounds  of  many,  24 


REF 


549 


SAP 


Proportions,  laws  of,  24 
limited,  24 
in  volumes,  331 
Protector,  Davy’s  87 
Proto-chloride  of  manganese , 255  (n) 
Protoxide  of  nitrogen,  141, 
decomposed,  143 
process  for,  142 
properties,  142 
Prussian  blue,  415 

constitution  of,  416 
Prussiate  of  mercury,  219 
potassa,  410 
Puddling  of  iron,  261 
Pulse  glass,  56 
Pulvis  antimonialis,  286 
Purification  of  alcohol,  441 
Purple  of  Cassius,  266 
Purpurate  of  ammonia,  see  Murexid,  431 
Purpuric  acid,  433 — 504 
Pus,  503 
Putrefaction,  490 

effluvia  from,  its  effects,  492 
Pyr acids,  theory  of,  366 
Pyrites,  iron,  260 
copper,  294 

Pyroligneous  acid,  37 6 
Pyrometer,  38 

Daniel’s,38 

Pyrophorus,  Homberg’s,  330 
Pyrophosphoric  acid,  174 
Pyrophosphates,  345 
Pyroxylic  spirit,  454 
uses  of,  454  [n] 

Pyrrhine,  132  [n] 


QTJADROXALATE  of  potassa,  372 
Quadro  chloride  of  nitrogen,  193 
analysis  of.  194 

Quantity  of  matter,  its  influence,  22 
Quevenne,  his  observations  on  yeast,  511 
Quinia , 435 

adulteration  of,  436 
disulphate  of,  436 
hydro-ferrocyanate  of,  436  [n] 

process  for,  435 

sulphate  of,  436 


RACEMOVINIC  ACID,  454 
Radiant  heat,  65 
Radiation  in  vacuo,  66 
theories  of,  70 
Radicals,  compound,  367 
Radical  vinegar,  376 
Ratios,  combining,  26 
Rays , luminous,  74 
calorific,  70 
chemical,  75 
Red  fire,  336,  [n] 
dyes,  456 

Refiner's  verditer,  352  [n] 


Reflection  of  heat,  67 
cold,  68 

Refraction,  double,  73 
of  light,  72 
of  inflammables,  72 
Regulus  of  antimony,  285 
Rennet,  501 
Resin,  alpha,  464 
beta, 464 
Resins,  463 

gum,  466 
solvents  ©f,  463 
dissolved  by  ether,  451 
solid,  465 

Respiration,  494—497 

consumption  of  oxygen  by,  498 

carbon  produced  by,  498 

Rhodio- chlorides,  359 
Rhodium,  319 
Rhodizonic  acid,  373 
Rhombohedral  system,  12 
Rocou,  458 
Rochelle  salt,  385 
Romd  de  Lisle's  theory,  7 
Roots,  483 
Rosin,  462 — 464 
I Rouge,  458  [n] 

Rum,  488 

Rumford's  experiments,  65 


SACCHAROMETER,  487 
Safety  lamp,  213 

principle  of  the,  213 

Saffron,  458 
Sago,  472 
Sal  ammoniac,  353 
native,  354 
Salicin,  436 
Saliva,  500 
Salop,  472 

Salt,  common,  chloride  of  sodium,  236 
Glauber’s,  322 
of  lemons,  371 
of  hartshorn,  491 
Salts , ammoniacal,  353 

atomic  composition  of,  104 
characters  of,  105 
composition  illustration  by,  25 
double,  104,  321 
haloid,  105,  358 
microcosm ic,  343 
neutral,  104 
orders  of,  104 
oxy,  320 

of  phosphuretted  hydrogen,  355 
saturated  solution  of  obtained,  4 (n) 

solution  of,  produces  cold,  52 
super,  104 
sulphur,  105,355 
Santalin,  458  (n) 

Sap  green,  486 


SIL 


550 


SPE 


Saratoga  waters,  iodine  in,  508 
Saturation,  3,  14 
Saturn,  sail  of,  379 
-Sauer  kraut,  acid  in,  380 
Saxon  blue,  457 
Scale  of  equivalents , 513 
Scheele’s  green,  345 
Sealing  wax,  464 
Sclerotium  giganteum,  393 
Sclerotin,  393 

Sea  salt , hydrochloric  acid  from,  185 
theory  of,  186 

Secondary  action,  98 
Seebeck's  experiments,  74 
Seeds,  485 
Seignette's  salt,  385 
Selenic  acid.  180 
Selenious  acid , 180 
Selenites,  180 
Selenium.  178 

bisulphuret  of,  221  (n) 

equivalent  of,  179 
sources  of,  178 
oxide  of,  179 
tinges  flame,  179 

Seleniuret  of  phosphorus,  221  (n) 

Seleniurets,  metallic,  227 
Seleniuretted  hydrogen,  217 
Seltzer  water,  349  (n) 

Senna,  484 
Sensible  heat.  53 
Serous  fluids,  503 
Sesquiferrocyanuret  of  iron,  415 
Serum,  497 

solid  matter  in,  496 
analysis  of,  497 
Signal  lights,  335  (n) 

Silica,  177 

in  blood,  496 
obtained,  177 
properties,  177 
U9es,  178 
Silicic  acid,  177 
Silico-fluorides,  361 
Silicon,  176 

obtained,  176 
oxide  of,  177 
properties,  176 
terchloride  of,  195  (n) 

Silver,  alloys  of,  311 

assay  of,  308  (n) 
chloride  of,  310 
cupellation  ol,  308  (n) 

cyanates  of,  401 
detonating,  310 
effect  of  galvanism  on,  95 
eliquation  of,  309,  (n) 
fulminating,  310 
glance,  311 
horn,  310 
ores  of,  307 
oxide  of,  309 
properties  of,  308 


Silver,  purification  of,  307 

solvent  of,  309,  337  (n) 
standard,  312 
sulphate  of  oxide  of,  329 
sulphuret  of,  311 
tarnish  of,  308 
tree,  310 

triphosphate  of  oxide  of,  344 
Silvering  for  dials,  312 
Simple  bodies  37 
Skin,  494 

affects  the  air,  499 
Smalt,  270 

Smells  removed  by  charcoal,  152 
. chlorine,  184 

Soap,  460 
Soda  alum,  331 
Soda,  bi-borate  of, '347 

a new  one,  347  (n) 

bi-carbonate  of,  349 
carbonate  of,  348 
distinguished,  235 
liquid. disinfecting,  349  (n) 
nitrate,  335 
powders,  385  (n) 
preparation  of,  see  Potassa 
properties  of,  235 
sesquicarbonate  of,  349 
sulphate  of,  322 
tartrate  of,  and  potassa,  385 
triphosphate  of,  343 
water,  349  (n) 

Sodium,  234 

bromide  of,  236  (n) 

chloride  of,  236 
fluoride  of,  236  [n] 

iodide  of,  236  [n] 
oxides  of,  235 
properties  of,  234 
proto-sulpluiret  of,  236 
protoxide  of,  235 
sesquioxide  of,  235 

Scemering’s  experiments  on  alcohol,  442 

Solar  phosphori,  77 

Solders,  300 

Solids-  expansion  of.  38 

Solubility,  tried,  4 [n] 

Solution,  defined,  3 
objects  of,  3 
produces  cold,  51 
saturated,  4 [n] 

Soot,  4S1 

Somerville’s  experiments,  75 
Sorbic  acid,  see  Malic  acid. 

Sorrel,  salt  of,  see  Oxalic  acid • 

Specific  gravity,  114 

changed,  16 
caloric,  48 

of  gases,  calculated,  33 
heat,  48 

Speculum  metal,  297 
Spectrum,  solar,  74 
Speiss,  270 


SUL 


551 


SUL 


Spelter , 263 
Spermaceti , 502 
oil,  503 
Spiroil.  469 
Spirit  of  wine , 488 
Spiritus  cetheris  nitrici , 453 
Spongy  platinum,  action  of  on  gases,  139 
carbonic  oxide,  161 

Squill,  483 
Stannates,  267 
Stark's  experiments,  67,  70 
Starch,  obtained*  471 

test,  prepared,  200  [n] 

converted  into  sugar,  471 
in  seeds,  485 
State  of  bodies,  50 
Steam  apparatus,  56,  59 
latent  beat  of,  58 
uses  of.  59 
Stearic  acid , 390 
Stearine,  502 
Steel,  227,  262 

alloyed,  263 

coated  with  gold,  &c.  451  [n] 
tempering  of,  262 

Stodartd's  exp’ts  on  coating  steel,  451  (n) 
Strasburg  turpentine,  464  (n) 

Stream  tin,  265  (n) 

Strontium,  239 

chloride  of,  240 
iodide  of,  240  (n)J 
obtained,  240 
peroxide  of,  240  (n) 
protoxide,  239 
Strontia,  carbonate  of,  350 
salts  of,  240 
sulphate,  324 
Strontianite,,  350 
Strychnine , 437 
Street  spirit  of  nitre , 453 
Sublimate , corrosive,  304 
Sublimation  of  benzoic  acid,  381 — 382 
Sub -acetate  of  lead,  379 
Sub  carbonate  af  ammonia,  350 
Substantive,  colours,  456 
Substitutions , theory  of,  366 
Succinamide,  468 
Succinates  376 
Succinic  acid,  375 
in  amber,  466 
Suet,  502 
Sugar , 469 

from  beets,  469 
acid  from,  374 
action  of  acids  on,  470 
of  grapes,  470 
of  starch,  471 
liquid,  470 
of  lead,  379 
Sulphamide,  468 
Sulphates,  characters  of,  321 

classification  of,  322  (n) 

decomposition  of,  227 
double,  330 

of  potassa  and  alumina,  330 


Sulphate,  of  alumina,  326 

of  ammonia,  323 
of  baryta,  323 
of  cobalt,  328 
copper,  328 
iron,  326 
lime,  325 
lithia,  323 
magnesia,  325 
mercury,  329 
nickel,  328 

oxide  of  ammonium,  323 

potassa,  322 

quihia,  436 

silver,  329 

soda  322, 

strontia,  324 

zinc,  327 

Sulphite  of  baryta,  332 
lime,  332 

Sulphites.  165  332 
Sulpho-cetic  acid  448 
Sulpho -cyanic  acid,  420 
Sulpho  hydric  ether,  452  (n) 

Sulpho -naphthalic  acid,  480 
Sulphur,  161 

acids,  355 
alcohol  of,  220 

combination  of  carbon  with,  22& 

■ metals  with.  226 

combustion  of,  162 
contains  hydrogen,  162 
crystallized,  161 
equivalent  of,  162 
flowers  of,  162 
vapour  of,  162 
salts,  355 

Sulphur et  of  Ethyl,  452 
Sulphurets,  action  of  heat  on,  226 
of  antimony,  287 
arsenic,  276 
iron,  259 

nitrogen,  221  (n) 

phosphorus,  221 
platinum,  318 
silver,  311 
tin,  267 
vanadium,  281 

Sulphuretted  hydrogen.  See  Hydrosulphx$~ 
ric  acid  gas. 

Sulphuric  acid,  165 

action  on  iron,  257 

on  oxamide,  467 

analysis  of,  167 
boiling  point,  167 
ether,  448 

manufacture  of,  165 

— illustrated,  166 

theory,  166 

of  Nordhausen,  165 
purified,  166 

strength  of  ascertained,  167 
test  of,  168 
uses,  168 


THE 


552 


URI 


Sulphurous  acid.  163 
analysis  of,  164 
bleuclies,  164 

convertible  into  sulphuric  acid,  164 
liquefied,  165 

Surface , influence  of  on  radiation,  66,  506 
Sweet  oil  of  wine,  451 
Sylvius,  salt  of,  378 
Symbols,  chemical,  33 
Berzelius’s,  35 
table  of,  34 

Sympathetic  ink,  270  (n) 

Synthesis,  36 

Systems  of  crystallization , 10 


TABLES  of  affinity,  18 

equivalent  weights  and  specific 
gravity  of  gases,  32 
freezing  mixtures,  51 
symbols,  34 
Tannic  acid,  388 

artificial,  390 
distinguished,  389 
varieties  of,  389 
Tannin,  388 
Tanno- gelatine,  389 
Tantalum,  same  as  Columbium,  284 
Tapioca,  472 
Tar,  464 

Tartar,  cream  of,  384 
emetic,  385 
Tartaric  acid,  383 

properties,  384 
a test,  384 

Tartrate,  of  antimony  and  potassa,  385 

iron  and  potassa.  385 

potassa,  384 

potassa  and  copper.  335 

and  soda,  385 

7'artrovinic  acid,  454 
Tellurium,  293 

action  of  nitric  acid  on,  293 
Tellurous  acid,  293 
Temperature,  43 

ascertained,  44 

changed  by  chemical  union,  16 

by  solution,  52 

influences  athnity,  21 
of  the  globe  equalized,  61 
of  steam,  58 
Tempering.  262 
Tendons , 494 
Terchloride  of  gold,  314 
Teriodide  of  nitrogen,  201 
Tests,  liquid,  14 
Test  papers,  made,  455  (n) 

Tetarto-carbo-hydrogen,  452  (n) 

Texture,  effect,  of,  63 
Thebaia,  440 
Theory  of  volumes,  31 
Thermometer,  44 

differential,  46 

reduction  to  mean  height  of  the,  42[n] 


Thermometer,  self  registering,  47 
Seix’s,  47,  new  viii 

Thermometers,  correspondence  between,  45 

Thialic  ether,  452 

Thionuric  acid,  429 

Third  body,  efiect  of  a,  17 

Thorium,  250 

Thorina,  250 

properties  of,  250 
Tin,  265 

acetate  of,  378 
alloys  of,  268 
chlorides  of,  267 
crystallized,  265  [n] 

filings,  265  [n] 

foil.,  265  [n] 
oxides  of,  266 
permuriate  of,  267 
properties,  265 
salts  of,  268 
sulphurets  of,  267 
Tincal,  317 
Titanium,  291 

metallic,  292 
oxides  of,  292 
Titanic  acid,  292 
Titano -fluorides,  361 
Tolu,  balsam  of,  465  (n) 

Torpedoes,  310 

Torrey's  apparatus  for  nitric  ether,  453 
Train  oil,  503 
! Triphosphates , 343 
of  lime,  344 
magnesia,  344 
oxide  of  silver,  344 
soda,  343 

Tube  apparatus,  117 
'Tungsten,  283 

chlorides  of,  284 
oxides  of,  283 
Tungstates,  284 
Tungstic  acid,  283 
'Tungsto- sulphurets,  358 
Turmeric,  456 
Turpentine , oil  of,  462 

Slrasburg,  464  [n] 

Venice,  464 
Turpeth  mineral,  329 
Tutenag , 297 

UNIT,  chemical,  29 

Union  of  sub  stances,  in  certain  proportions, 
23 

Uramil,  429 
Uramilic  acid,  430 
Uranium,  289 

oxides  of,  289 
Urea,  399—504 

compounds  of,  400 
t/re’s  drying  apparatus,  59  (n) 

Urets,  what,  103 
Uric  oxide,  433 
acid,  504 
Urine,  504 


WOL 


VOL  553 


Urine , phosphate  of  ammonia  and  magnesia 
in,  344 

urea  from,  400 
component  parts  of,  504 
VAN  ABIC  ACID , 281 
Vanadium,  280 

oxides  of,  281 
sulpliurets  of,  281 
Vaporization,  54 
Vapours,  dilatation  of,  51 

table  of  elastic  force  of,  520 

aqueous,  517,518 

Varnishes,  464 
Varvacite,  253  (n) 

Vegetable  acids,  369 
alkali,  232 
bodies,  362 
principles,  362 

form  definite  compounds,  363 

classes  of,  363 

soil,  490 

Vegetables,  alkalies  in,  434 

distinguished,  434 

decompose  water,  134 
growth  &c.,  affected  by  light,  76 
decomposition  of,  490 

of  carbonic  acid  by,  157 

products  of  destructive  distillation  of, 
477 

principles  in,  362 

neutral,  467 

Venice  turpentine,  464 
Ventilation,  41 
Ver atria,  437 
Verdigris,  379 

composition  of,  379  (n) 

Verditer,  352 
Verjuice,  470 
Vermilion,  306 

Vernier’s  process,  for  oxide  of  phosphorus, 
172  (n) 

Vinegar,  376 — 489 
distilled,  376 

Vinous  fermentation,  487 
Viscin,  475  (n) 

Vision,  71 

Vitriol,  blue,  See  Copper,  sulphate  of,  328 
green.  See  Iron,  sulphate  of,  326 
white,  See  Zinc,  sulphate  of,  327 
oil  of,  table  of,  521 
Volatile  oils,  461 
obtained,  461 
action  of  acids  upon,  462 
quantity  afforded  by  various  seeds,  &c, 
462  (n) 

Volta’s  eudiometer,  138 
pile,  90 

crown  of  cups,  90 
theory,  85,  92 

evidence  against,  93 

Voltaic  electricity,  85,  88 
circles,  85,  88 

— without  metals,  88 

chemical  effects  of,  96 
Davy’s  experiments,  96 
effect  on  metals,  95 

70 


Voltaic  electricity,  Faraday’s  experiments, 93 
magnetic  effects  of,  102 
new  terms,  98 
WASH,  487  (n) 

Water,  action  of  on  lead,  298 
analysis  of,  131 

by  galvanism,  96 

by  vegetables,  132 

apparatus  for  showing1  the  composi- 
tion of,  131 

— « decomposition  of,  96,  131 

basic,  5 

composition  of,  129 

illustrated,  130 

compressible,  133 
constitutional,  5 

* removed,  5 

contains  air,  133 
of  crystallization,  5 
decomposed  by  galvanism,  96,  131 

by  potassium,  231 

distilled,  132 
expands  by  cold,  43 
frozen  by  ether,  450 

by  rapid  evaporation,  60 

gilding,  316 
hard,  325 
of  ammonia,  210 

process  for,  211  (n) 

maximum  density  of,  43 

not  essential  in  voltaic  circles,  87 

properties  of,  132 

quantity  of  gas  absorbed  by,  133  (n) 
quantity  of  denoted,  5 
Seltzer,  349  (n ) 
a slow  conductor,  65 
soda,  349  (n) 

standard  weight  and^measure  of,132(n) 
Waters,  distilled,  462 
Wax,  460 

bees,  460 
cow  tree,  461 
myrtle,  461 
sealing,  464 
Weight,  2 

atomic,  30 
of  gases,  32 

Weights  and  measures,  525 
Weiss  his  systems  of  crystals,  10 
Wells’  experiments,  62 
Welther’s  tube,  187  (n) 

Wenzel’s  law,  27 
Wheat  four,  471 
JVhey,  501 

White  oxide  of  bismuth,  291 
flux,  333  (n) 
lead,  299 
pearl,  291 
vitriol,  327 

Wilson’s  phosphorus,  77  (n) 

Wine,  488 

heavy  oil  of,  454 
light  oil  of,  452 
sweet  oil  of,  451 
odour  of,  to  what  owing,  488 
Wire  gauze,  effect  of,  78 


YTT 


554 


ZIR 


Wollaston's  cryophorus,  61  (n) 

scale,  29,  513 
theory  of  crystals,  8 
theory  of  galvanism,  92 
thermometer,  56 

Woods , quantity  of  oxygen  required  for 
combustion,  484 

Wood,  affords  oxalic  acid,  370  (n) 

pyroxylic  spirit,  454 

Woody  fibres,  483 
Wool , 494 

XANTHIC  OXIDE,  433 
Xyloidin , 473 

YELLOW  DYES,  457 
Yellow,  King’s,  277 
acid,  492 
Yttria,  249 
Yttrium,  219 

properties  of,  249 
salts  of,  249 


ZAFFRE,  270 
Zanthin,  458  (n) 

Zeine,  475  (n) 

Zinc,  acetate  of,  378 

amalgamated,  87  [nj 
blende,  264 
chloride  of,  263 
circle,  86 

combustion  of  in  oxygen  gas,  120 
flowers  of,  263 
for  hydrogen  gas,  263  [n] 
properties,  263 
protoxide  of,  263 
sulphate  of  protoxide,  327 
uses  of,  264 
Zirconia,  251 

properties  of,  251 
Zirconium,  250 

properties,  251 
sesquioxide  of,  251 


INDEX 


TO  THE  FIGURES  OF  APPARATUS,  &c. 


Fig. 

JACKSON’S  oxyalcohol  lamp,  1,  2 Front. 
Air  Pump,  5,  6 do. 

De  Luc’s  columns,  7 do. 

Dish  for  freezing  water,  8 do. 

Clarke’s  electro-mag.  machine,  9,  10  do. 
New  thermometer,  11  do. 

Adams’  apparatus  for  solidifying 

carbonic  acid  gas,  1,2  PI.  I. 

Do.  for  washing  precipitates,  1,  2 P1.1I. 
Galin’s  cylinder  holder,  3,4,  5 do. 

Condensing  apparatus,  6 do. 

Cooper’s  mercurial  receiver,  7 do. 

Seffstroem’s  support,  8 do. 

Hare’s  app’ts  for  hyd.  and  chlorine,  9 do. 
Haiiy’s  primitive  forms,?  1 to  6 Page 8 
Daniell’s  method  of  developing 

crystalline  structure,  7 8 

Simple  and  compound  forms,  8 to  13  9 

Weiss’s  system  of  crystalliza- 
tion, 14  to  20  11 

Apparatus  for  hydrochlorate  of 

ammonia,  21  15 

Pyrometer,  22  38 

Apparatus  for  illustrating  the 

expansion  of  liquids,  23  39 

Do.  do.  do-  24  to  25  40 

Do.  do.  of  air,  26  41 

Do.  change  of  specific  gravity 

in  liquids  by  heat,  27  41 

Do.  ascent  of  heated  air,  28  41 

Thermometers,  29  to  34  46 

Apparatus  for  illustrating  ca- 
pacity of  bodies  for  heat,  35  48 

Do.  evolution  of  heat  by  con- 
densation of  air,  36  50 

Do.  for  freezing  mercury,  37  53 

Pulse  glass,  or  manometer,  38  56 

Apparatus  for  illustrating  the 
effect  of  diminished  pressure 
on  the  boiling  point,  39  56 

Marcet’s  apparatus  for  increas- 
ed pressure,  &c.  40  56 


Fig.  Page 

Marcet’s  ap’ts  for  freezing  mercury,  41  57 

Henry’s  do,  for  boiling,  &c.  42  58 

Wollaston’s  steam  tube,  43  59 

Leslie’s  method  offreezing  wa- 
ter in  vacuo,  44  60 

Cryophorus,  45  61 

Marcet’s  modification  46  61 

Hare’s  apparatus  for  exhibit- 
ing the  conduction  of  water,  47  64 

Rumford’s  do.  do.  do.  48  65 

Davy’s  do.  do,  the  ra- 
diation of  heat  in  vacuo,  49  66 

Bache’s  do.  absorption,  &c.  of  beat,  50  66 

Pictet’s  do.  illustrating  the 

radiation  ofheat,  51  68 

Diagram  illustrating  the  re- 
fraction of  light,  52  72 

Ignition  of  platinum  wire,  53  78 

A phlogistic  lamp,  54  78 

Electrometer,  55  80 

Series  of  electrical  conductors,  56  81 

Electrophorus,  57  84 

Voltaic  circles,  58,  59  86 

Simple  circle,  60  88 

Circular  arrangemeut,  61,  62  89 

Hare’s  calorimotor,  63  89 

Method  of  forming  copper  and 

zinc  plates,  64,  65  89 

Crown  of  cups,  66  90 

Voltaic  pile,  67  90 

■ trough,  6C,  69,  70  90 

Wollaston’s  Plates,  71  91 

Hare’s  deflagrator,  72  to  74  91 

Figure’s  illustrating  Faraday’s 
experiments,  75  to  78  93 

Arrangements  for  decomposing 
water  by  galvanism,  79  to  81  96 

Davy’s  cups,  82  97 

Arrangement  for  transfer  of 

acid  and  alkali,  83  97 

Faraday’s  voltameter  84  100 

Gas  bottles,  85  to  87  106 


556 


»>  < 1 

Fig. 

Page 

Flexible  tube. 

88 

106 

Iron  gas  bottles, 

89,  90 

107 

Apparatus  for  manipulating 

with  gases, 

91  to  9o 

107 

Pneumatic  troughs. 

96,  97 

108 

Graduated  tube, 

98 

108 

Gas  funnel. 

99 

108 

Gasometer, 

100 

108 

Gas  holder, 

101 

109 

of  Pepys, 

102 

109 

of  Hope, 

103—4 

no 

Newmann’s  mercurial  trough, 

, 105 

no 

Detonating  tube, 

106 

in 

Furnaces, 

107—110 

in 

Apparatus  for  submitting  _ 
to  electricity,  111 

Pepy’s  transferring  tube,  112 

Transferring  of  gases  from  tubes  113 
Hydrostatic  balance,  114 

Leslie’s  apparatus  for  taking 
specific  gravity  of  powders,  115 
Jars  for  combust’n  in  ox. gas,  116 — 1 IS 
Gay  Lussac’s  hyd.  gas  ap’ts,  119 
Hare’s  hyd.  gas  reservoir,  self- 

regulating,  120 

Bladder  and  pipe  for  hyd.  gas,  121 
Arrangement  for  extinguishing 

dame  in  hyd.  gas,  122 

Dobereiner’s  lamp,  123 

Electrical  pistol,  121 

Small  calorimotor  for  explod- 
ing gases,  125 

Tube  for  exploding  gases,  126 

Arrangement  for  do.  by  electricity,  127 
Hare’s  compound  blow  pipe,  123 

Concentric  jet  for  do.  129 

Brooke’s  blow  pipe,  130 

Apparatus  for  the  formation  of 

water,  131  to  133 

Do.  for  decomposition  of  do. 

by  iron,  134 

Do.  do.  do.  do.  by  galvanism,  135 

Distillation,  136 

App’ts  for  obtaining  nitrogen,  137, 138 
Ure’s  eudiometer,  130 

Apparatus  for  decomposition  of 

protoxide  of  nitrogen,  140 

Do.  for  distillation  of  nitric 
acid,  141,  142 

Do.  for  action  of  nitric  acid 
and  phosphorus,  143 

Do.  for  carbonic  acid  gas,  144, 145 
Nooth’s  apparatus,  146 

Apparatus  for  exhibiting  the 

escape  of  carbonic  acid,  147 

Do.  for  ascertaining  loss  of  do.  148 

Alkalimeter,  149 

Apparatus  for  sulphurous  acid,  150 

Reid’s  mercurial  trough,  151 


112 

113 

114 

115 

116 
120 
123 

123 

124 

124 

125 
125 

125 

126 
126 
127 
127 
12S 

130 

131 

131 

132 

131 

13S 

143 

14S 

150 

154 

151 

155 

158 

159 
163 
163 


Apparatus  for  illustrating  the 
formation  of  sulphuric  acid. 

Do.  for  phosphorus, 

Do.  for  combustion  of  phos- 
phorus in  oxygen  gas,  154, 

Do.  for  oxidation  of  phosphorus, 
Do.  for  chlorine  gas, 

Do.  for  combustion  in  do.  158, 

Davy’s  do.  do.  of  charcoal  in  do.* 
Woulfe’s  apparatus. 

Apparatus  for  hvpochlorous 
acid  gas,  (Euchlorine)  162, 

Glass  syringe  for  taking  up  chlo- 
ride of  nitrogen, 

Apparatus  for  iodine, 

Do.  for  passing  gases  into  liquids. 
Do.  for  hydrofluoric  acid. 

Do.  fur  ammoniacal  gas, 

Do.  for  decomposing  do. 

Do.  for  exhibiting  the  action  of 
chlorine  and  ammonia, 

Do.  for  obtaining  aqua  ammonia. 
Do.  for  do.  do.  do. 

Method  of  illustrating  the  effect 
of  wire  gauze, 

Davy's  safety-lamp,  174, 

Apparatus  for  phosphuretted  hyd. 
Do.  for  bisulphuret  of  carbon, 

Ure’s  instrument  for  testing 
chloride  of  lime. 

Marsh’s  apparatus  for  detecting 
arsenic,  179, 

Berzelius’s  tube  for  reduction 
Matras  for  red  precipitate, 

Cupel  mould, 

Muffle, 

Cupelling  furnace, 

Apparatus  for  illustrating  the 
formation  of  sal  ammoniac, 

Do.  for  hydrosulphate  of  ammonia, 
Sublimation  of  benzoic  acid, 
Apparatus  for  hydrocyanic  acid. 
Do.  for  condensation  of  alcohol 
and  water, 

Hydrometer, 

Apparatus  for  sulphuric  ether,  192, 
Do.  for  freezing  with  ether, 
Torrey’s  apparatus  for  nitric  ether, 
Italian  recipient  for  distillation 
of  oils, 

Apparatus  for  oil  gas, 
Saccharometer, 

Apparatus  for  fermentation. 
Apparatus  for  potassium, 

Alcohol  lamps,  &c. , 


* This  also  answers  for  decomposing  by* 
drosulphuric  acid  gas  by  galvanism. 


Fig. 

Page 

152 

166 

153 

169 

,155 

170 

156 

174 

157 

181 

159 

183 

160 

183 

161 

187 

163 

190 

164 

194 

165 

197 

166 

200 

167 

206 

168 

208 

169 

210 

170 

210 

171 

210 

172 

211 

173 

213 

175 

213 

176 

218 

177 

221 

178 

243 

180 

274 

181 

274 

182 

302 

1S3 

308 

184 

308 

185 

309 

186 

354 

187 

355 

188 

382 

189 

405 

190 

442 

191 

443 

,193 

448 

194 

450 

,195 

453 

196 

461 

197 

481 

198 

487 

199 

488 

528 

529 

